Natural cellulose fibers from Agave Americana L. ASPARAGACEAE as an effective adsorbent for mercury in aqueous solutions

Adso p ion (2025) 31:40 h ps://doi.o g/10.1007/s10450-024-00590-4 coppe (Cu), zinc (Zn), lead (Pb), ch omium (C ), nickel (Ni), and me cu y (Hg) a e ha m ul by-p oduc s o hese indus ial p ocesses [1, 2]. Once in oduced in o he en i- onmen , hese me als dispe se h ough ai , soil, and wa e , accumula ing in li ing o ganisms due o hei non-biode- g adable na u e [3]. Thei oxici y is especially ala ming o aqua ic li e and can ha e de imen al e ec s on human heal h, e en a e y low concen a ions [4, 5].The impac o hea y me al pollu ion ex ends beyond heal h issues, sig- ni ican ly a ec ing he economic s abili y and quali y o li e o he a ec ed communi ies [6]. Among hea y me als, me cu y is conside ed one o he mos haza dous due o i s high oxici y and capaci y o bioaccumula ion [7]. Exces- si e me cu y in ake poses signi ican isks o he cen al ne ous, diges i e, and enal sys ems in humans [8]. The Wo ld Heal h O ganiza ion (WHO) ecommends a maxi- mum allowable limi o 0.006 mg/L o mine al me cu y in d inking wa e , wi h a o al daily in ake no exceeding 2 µg/ 1 In oduc ion Hea y me al pollu ion, pa icula ly ha which a ises om ac i i ies such as mining, ba e y p oduc ion, and he pha - maceu ical indus y, poses a se ious isk o bo h he en i- onmen and public heal h. Me als such as cadmium (Cd), Lou des Ga cía-Rod íguez [email p o ec ed] Hugo Sánchez-Mo eno [email p o ec ed] 1 G upo de In es igación de Ene gías Al e na i as y Ambien e, Facul ad de Ciencias, Escuela Supe io Poli écnica de Chimbo azo (ESPOCH), Paname icana Su Km 1 ½, EC060155 Chimbo azo, Ecuado 2 Depa amen o de Ingenie ía Ene gé ica, Escuela Técnica Supe io de Ingenie ía (ETSI), Uni e sidad de Se illa. ETSI, Camino de Los Descub imien os, s/n, Se illa 41092, Spain Abs ac This s udy in es iga ed he use o unc ionalized cabuya ibe s (FCF) as an e ec i e adso ben o Hg (II) emo al om aqueous solu ions. The composi ion, su ace p ope ies, and mo phology o he FCF we e cha ac e ized by scanning elec on mic oscopy (SEM), ene gy dispe si e X- ay spec ome y (EDS), and Fou ie ans o m in a ed spec oscopy (FTIR). The e ec s o he pH, con ac ime, empe a u e, adso ben dosage, and ini ial Hg (II) concen a ion on he adso p- ion p ocess we e s udied. Unde op imized expe imen al condi ions, FCF achie ed a emo al e iciency exceeding 92%, wi h a maximum adso p ion capaci y o 8.29 mg/g. The expe imen al da a o he FCF iso he m we e analyzed using he Langmui , F eundlich, DR, and Temkin adso p ion models. No ably, he Langmui iso he m exhibi ed he highes R² alue o 0.99, indica ing he model’s s ong applicabili y. The pseudo-second-o de kine ic model k2 = 0.42 mg/g.min was employed o elucida e he adso p ion mechanism. The modynamic s udies o he adso ben FCF we e conduc ed, and ΔG° (-6.16 kJ/mol), ΔH° (36.29 kJ/mol), and ΔS° (141.98 kJ/mol·K) we e calcula ed, assessing he easibili y o he p ocess. Addi ionally, he deso p ion esul s o FCF we e e alua ed, demons a ing ha i can be eused o up o h ee cycles, achie ing adso p ion a es o 74% and 62% in he hi d cycle. This indica es i s s abili y and ecycling capaci y. Finally, he e ec i eness o he FCF was demons a ed by elimina ing app oxima ely 91% o Hg (II) om eal mine al wa e samples in Ecuado . These esul s highligh he p o FCF as p omising, eco- iendly, and sus ainable adso ben s o he emedia ion o Hg (II) con amina ion in aqua ic sys ems. Keywo ds Hg (II) adso p ion · Mining was ewa e ea men · Adso p ion iso he m · Kine ic models · Adso p ion iso he ms · Na u al ibe s Recei ed: 6 No embe 2024 / Re ised: 16 Decembe 2024 / Accep ed: 26 Decembe 2024 / Published online: 31 Janua y 2025 © The Au ho (s) 2025 Na u al cellulose ibe s om Aga e Ame icana L. ASPARAGACEAE as an e ec i e adso ben o me cu y in aqueous solu ions HugoSánchez-Mo eno1· Lou desGa cía-Rod íguez2· CelsoRecalde-Mo eno1 1 3 Adso p ion (2025) 31:40 kg o body weigh [9]. The e o e, he emo al o Hg (II) om aqueous solu ions is essen ial, highligh ing he need o e ec i e me hods o elimina e Hg (II) [10]. Common emedia ion echniques o he elimina ion o con aminan s om was ewa e , such as chemical p ecipi a ion [11], ion exchange [12], e e se osmosis [13], coagula ion [14], elec ochemical ea men s [15], and memb ane p ocesses, ha e been epo ed in he li e a u e [16]. Howe e , mos o hese me hods ha e some disad an ages such as high cos , oxic was e p oduc ion, educed e iciency, and high ene gy consump ion [17]. Adso p ion is conside ed one o he bes was ewa e ea men echniques and has ecei ed consid- e able a en ion due o i s ope a ional easibili y, simple design, high e iciency in con aminan emo al, as well as i s ecyclabili y and eusabili y [18, 19]. In ecen yea s, nume ous s udies ha e been conduc ed o iden i y sus ainable and cos -e ec i e adso ben s de i ed om na u al biomass [20]. Among hese ma e ials, cellu- losic biomass has ga ne ed signi ican in e es due o i s low cos and abundance [21]. This ype o biomass is cha ac e - ized by i s high numbe o hyd oxyl g oups on he su ace, which acili a es modi ica ion, as well as i s excellen spe- ci ic esis ance, la ge su ace a ea, and ema kable he mal and chemical s abili ies [22, 23]. Examples o cellulosic biomass include Ame ican aga e [24], lax ibe s [25], Cis- sus quad angula is Linn plan [26], and palm oil ibe s [27]. Plan ibe s a e known as he mos abundan enewable esou ce in na u e, composed mainly o cellulose, hemicel- lulose, and lignin, wi h a hie a chical s uc u e ha spans om he me ic scale o he nanome ic scale [28]. In his con ex , aga e is p esen ed as a g oup o dese plan s belonging o he monoco amily Aga aceae [29]. I is cha ac e ized by i s spiny lea es, which p oduce a a ie y o ibe s [30]. Despi e hei abundan a ailabili y and en i- onmen al sus ainabili y, aga e ibe s ha e ye o achie e signi ican economic alue [31]. I has been demons a ed ha aga e ibe s a e highly e ec i e adso ben s o he emo al o dyes and ch omium om [29]. Howe e , despi e hei ema kable adso p ion capaci y, he p ope ies o hese ibe s in cap u ing hea y me al ions ha e ye o be explo ed in dep h. In his s udy, he main objec i es we e o explo e he emo al e icacy and adso p ion mechanism o Hg (II) on cabuya (Aga e Ame icana L. ASPARAGACEAE) ibe s unc ionalized wi h NaOH (FCF). A se ies o cha ac e iza- ions, such as FTIR, SEM, and EDS, we e conduc ed o in es iga e he physicochemical p ope ies. The esis ance o en i onmen al exposu e was examined agains pH le els and empe a u e, as well as he eusabili y o FCF. Subse- quen ly, adso p ion kine ics, iso he ms, and he modynam- ics we e s udied o in es iga e he adso p ion p ope ies o Hg (II) on FCF. The p ac ical applica ion o FCF in eal wa e bodies was also explo ed, speci ically in was ewa e om a isanal mining a he Vi gen de las Nie es Bene icia- ion Plan in Za uma. Th ough his comp ehensi e app oach, i is expec ed no only o con ibu e o he unde s anding o he adso p ion capaci y o Hg (II) on FCF bu also o p o- ide a iable solu ion o he emedia ion o con amina ed wa e s in Ecuado . This add esses a signi ican en i onmen- al issue and p omo es public heal h, ma king a s ep o wa d in s a egies o mi iga ing hea y me al con amina ion in a coun y wi h abundan ege a ion o Aga e. 2 Ma e ials and me hods 2.1 Reagen s and ma e ials Ame ican Aga e L. ASPARAGACEAE was collec ed in he cen e o he in e -Andean egion o Ecuado , in he Rio- bamba sec o . The bioso ben was ea ed wi h aqueous solu ions o app op ia e concen a ions p epa ed using NaOH, which was acqui ed om ISOLAB Labo ge a e GmbH, We heim, Ge many. The Hg (II) s anda d solu- ion o 1000 mg/L was acqui ed om AccuS anda d (New Ha en, Connec icu , USA). HCl and HNO3 we e pu chased om LOBA CHEMIE PVT. L d. All chemicals and sol en s used in his s udy we e o analy ical g ade, and no addi ional pu i ica ion sys ems we e equi ed. Milli-Q wa e was used o p epa e he solu ions ( esis i i y: 18.2 MΩ.cm a 298 K). 2.2 Me hods Cabuya lea es we e collec ed and unc ionalized by sal hyd olysis a 40 °C o 4 h. The esul ing FCF we e washed o emo e non-cellulosic compounds and we e cha ac e - ized using SEM, EDX, and FTIR. The FCF we e hen es ed as Hg (II) abso ben s wi h me cu y solu ions o known con- cen a ions placed in con ac wi h he FCF. The e ec s o a ious ac o s, including he con ac ime, sample dose, pH, empe a u e, and concen a ion, we e eco ded o de e mine he amoun o Hg (II) e ained. Me cu y adso p- ion was analyzed using a omic abso p ion spec oscopy. To de e mine he ype o adso p ion be ween he FCF and analy e, an adso p ion iso he m es was pe o med, which e alua ed he equilib ium da a based on he Langmui and F eundlich iso he m models unde expe imen al condi ions. Addi ionally, he adso p ion kine ics o me cu y in he FCF we e s udied by i ing he expe imen al da a o pseudo- i s - o de and pseudo-second-o de kine ic models. 1 3 40 Page 2 o 27 Adso p ion (2025) 31:40 3 Expe imen a ion 3.1 P epa a ion o FCF The ex ac ion o na u al ibe s poses a conside able chal- lenge in he p ocessing o plan ibe s. Lea es o black cabuya (Aga e ame icana L. ASPARAGACEAE) we e col- lec ed, which ini ially exhibi ed a g ay-g een colo . The ibe s om he plan we e manually ex ac ed, and he ho ns om he edges we e immed (Kozłowski e al., 2020). The collec ed ibe s unde wen a pu i ica ion and unc ionaliza- ion p ocess using a 5% (w/ ) sodium hyd oxide (NaOH) solu ion, which is gene ally op imal o mos na u al ibe s na u ales [32].This p ocess was ca ied ou a a empe a- u e o a ound 40 °C o a pe iod o 4 h [33]. Subsequen ly, he ea ed ibe s we e epea edly washed wi h deionized wa e using ul asonic cleaning equipmen un il a pH o 6 was eached. Finally, he unc ionalized cabuya ibe s (FCF) we e d ied in an o en a 75 °C o 24 h o emo e excess wa e [34]. 3.2 Cha ac e iza ion s udies The mic os uc u e o he FCF was analyzed using a Nikon Eclipse E200 da a acquisi ion op ical mic oscope wi h a pa a ocal leng h o 60 mm and a 10X ield o iew scanning elec on mic oscope (SEM, JSM-IT100LA). The samples we e moun ed on s ubs wi h double-sided adhesi e ape and coa ed wi h a hin laye o e apo a ed gold (Au) [35]. The FTIR spec um o he FCF was ob ained using a Fou- ie ans o m in a ed spec ome e (JASCO FT/IR-4100) om 4000 o 560 cm−1. The co esponding g aph was ans- o med in o a peak abso bance g aph wi h a esolu ion o 16 cm−1. 3.3 Feasibili y o FCF as hg (II) e aine s in wa e To es ablish he capaci y o he FCF o e ain me cu y, a ce i ied me cu y (II) s anda d o 1000 mg/L was used, and solu ion o 1.0 mg/L was p epa ed o a ious assays (e ec o con ac ime, adso ben quan i y, agi a ion, ini ial Hg (II) concen a ion, pH, and empe a u e). These solu ions we e placed in con ac wi h he FCF and once equilib ium was eached, he pe cen age o me cu y adso bed o each es was de e mined using a omic abso p ion spec ome y. 3.3.1 E ec o con ac ime The adso p ion o Hg (II) me al ions was measu ed by plac- ing 0.5 and 1.0 g o FCF in a lask con aining 100 mL o a solu ion o me cu y (1.0 mg/L) wi hou pH adjus men . The con en s o he lask we e agi a ed unde ul asound o 60 s and mechanical agi a ion was con inued a 150 pm o 24 h a a cons an empe a u e o 25 °C. Samples o he liquid phase (1 mL) we e collec ed a ime in e als o 5, 10, 15, 30, and 60 min, and hen a 2 h and 4 h. A e each aliquo was aken, i was i a ed o 10 mL wi h deionized wa e and me cu y e en ion was de e mined by a omic abso p ion spec oscopy. 3.3.2 E ec o adso ben quan i y (FCF) The e ec o he FCF quan i y on me cu y e en ion was de e mined by a ying he adso ben dose o each assay (0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 g) in a ixed- olume lask con aining 100 mL o a solu ion wi h a 1.0 mg/L me cu y ion concen a ion a a empe a u e o 25 °C wi hou pH adjus men . The con en s o he lask we e shaken unde ul asound o 60 s and mechanically agi a ed a 150 pm un il equilib ium was eached. An aliquo o 1 mL was hen aken and dilu ed o 10.0 mL wi h deionized wa e , and he concen a ion o he e ained me cu y was de e mined using a omic abso p ion spec oscopy equipmen . 3.3.3 E ec o empe a u e The e ec o empe a u e was e alua ed wi h alues be ween 25, 35, and 45 °C, o which he op imal condi- ions o FCF iden i ied in Sec . 3.3.1 and 3.3.2, which we e he equilib ium ime and dosage o he sample, p ese ing a concen a ion o 1.0 mg/L o me cu y, a a olume o 100 mL, wi hou pH adjus men . Once equilib ium was eached, aliquo s o 1 mL we e aken, illed o he 10.0 mL calib a- ion ma k, and he me cu y concen a ion was de e mined by a omic abso p ion spec oscopy. 3.3.4 E ec o pH on e en ion The poin o ze o cha ge (PZC) o FCF biomass was cal- cula ed by mixing 50 mg o FCF wi h 10 ml o a 0.01 M NaCl elec oly e solu ion. The ini ial pH was adjus ed using 0.1 M NaOH and 0.1 M HCl, and he mix u e was agi a ed o 24 h a oom empe a u e. The pH o he il a e was measu ed a e il e ing, and he PZC was de e mined as he in e sec ion o he cu e wi h he y-axis = 0. To s udy he e ec o pH on Hg (II) adso p ion, di e en solu ions we e p epa ed a pH alues o 3.0, 5.0, 7.0, and 9.0, wi h me cu y concen a ion o 1.0 mg/L o me cu y. The adso - ben samples we e added o a s able olume o 100 mL o each p epa ed solu ion, and he con ac ime was eached. The me cu y concen a ion was de e mined using a omic abso p ion spec oscopy and he pH was adjus ed using analy ical-g ade HCl and NaOH. 1 3 Page 3 o 27 40 Adso p ion (2025) 31:40 FCF we e placed in 100 mL o a solu ion o HCl and HNO3 wi h concen a ions o 0.1 mol L−1 in di e en assays, wi h 150 pm agi a ion a 25 °C o 8 h. The deso p ion p ocess was pe o med in duplica e du ing one deso p ion cycle. Once he es was comple ed, he e ained me cu y concen a ion was de e mined using a omic abso p ion spec oscopy. 3.7 Re en ion Capaci y in hg (II)-Fo i ied Real Wa e samples To e alua e he me cu y e en ion capaci y o he FCF, sam- ples o me cu y-con amina ed was ewa e om he gold ex ac ion sys ems o he Vi gen de las Nie es Bene icia ion Plan in Za uma, Ecuado (Sou h Ame ica) we e used. Mine wa e (100 mL) was collec ed, and Hg (II) concen a ions o 10 mg/L, 20 mg/L, and 30 mg/L we e added o ob ain a o i ied sample. The mine wa e used was ob ained om ou sampling poin s: he en ance, exi , gold ex ac ion poin s, and was ewa e discha ge pool. The o i ied mine wa e was b ough in o con ac wi h 1.0 g o FCF and agi- a ed un il an equilib ium was eached. A e equilib ium, aliquo s o 1.0 mL we e aken, dilu ed o 10 mL, diges ed, and he me cu y concen a ion was de e mined by a omic abso p ion spec oscopy. 4 Resul s and discussion 4.1 Cha ac e iza ion o FCF 4.1.1 Scanning elec on mic oscopy (SEM) and ene gy- dispe sed spec oscopy (EDS) Figu e 1 shows he mo phology o he cellulose su ace wi h inc ease o 800X (Fig. 1a) and 370X (Fig. 1b). The SEM mic og aphs show he s uc u e o long, hick, and FCF wi h an a e age diame e o 65 μm. A s udy by [38] he Uni e - si y o São Paulo epo ed a diame e o app oxima ely 50 μm. On he o he hand, Fig. 1b depic s a smoo h su ace s uc u e o ib ils wi h uni o m sizes, due o ea men wi h sodium hyd oxide, which success ully emo ed impu i ies. In Fig. 1a, holes wi h an a e age size o 3 μm we e obse ed. The EDS analysis o he FCF is p esen ed in Fig. 2, namely, he a ea analyzed (Fig. 2a) and i s spec um (Fig. 2b). The EDS mapping o he ibe e ealed he p esence o ca bon, oxygen, and gold. Speci ically, he p esence o ca bon and oxygen indica es ha he e we e no impu i ies in he o he elemen . In addi ion, he appea ance o gold was because he ibe s we e coa ed wi h a hin laye o gold o make hem conduc i e. Finally, he spec um indica es an 3.3.5 E ec o ini ial hg (II) concen a ion The e ec o he ini ial Hg (II) concen a ion on adso p ion by he FCF ob ained was ca ied ou by placing 1.0 g o d y FCF ibe s in a se ies o lasks con aining 100 mL o me al ions a de ined concen a ions (10–100 mg/L), wi hou pH adjus men . The con en s o he lasks we e agi a ed a 150 pm and 25 °C o 120 min. A e adso p ion, he esidual concen a ion o he me al ions was de e mined using a omic abso p ion spec oscopy. 3.3.6 E ec o agi a ion The e ec o agi a ion on Hg (II) adso p ion was de e mined o analyze he in luence o his ac o . Fo his pu pose, an ini ial me cu y concen a ion o 10 mg/L was p epa ed, main aining pa ame e s such as an adso ben dose o 1.0 g, con ac ime o 120 min, pH o 5, and a cons an empe a u e o 25 °C. Tes s we e pe o med wi h and wi hou agi a ion. A e adso p ion, he inal me cu y concen a ion was de e - mined by a omic abso p ion spec oscopy. 3.4 Adso p ion iso he m and adso p ion kine ics The adso p ion iso he m desc ibes he equilib ium o a ma e ial on a su ace based on he ela ionship be ween adso ba e concen a ion and adso bed [36]. In his s udy, Langmui , F eundlich, Temkin and Dubinin-RudushKe - ich adso p ion iso he ms we e in es iga ed o iden i y he bes iso he mal model o desc ibing me cu y adso p ion in FCF. Addi ionally, a undamen al aspec was add essed using kine ic analysis, which p o ided a desc ip ion o he a e and mechanism o Hg (II) adso p ion. To his end, he adso p ion kine ics o Hg (II) we e s udied by i ing he expe imen al da a o he pseudo- i s -o de , pseudo-second- o de , and Elo ich kine ic models. 3.5 The modynamic s udy The he modynamic adso p ion model is mainly used o cha ac e ize he he modynamic p ope ies o he adso p ion p ocess by p o iding in o ma ion on he mechanism o he empe a u e e ec s on he wa e -me cu y in e ace adso p- ion [37]. To his end, he he modynamic pa ame e s o he adso p ion o Hg (II) ions in FCF we e s udied h ough he changes o Gibbs ee ene gy, en opy and en halpy modi y- ing he empe a u e o he sys em be ween 25 °C and 40 °C. 3.6 Deso p ion analysis Once he adso p ion p ocess was comple e, wo leaching agen s we e used o assess Hg (II) e en ion. Hg (II)-loaded 1 3 40 Page 4 o 27 Adso p ion (2025) 31:40 a signi ican inc ease in he ela i e in ensi y o he OH band om 3332 cm o 1 o 3370 cm−1, a dec ease in he in ensi y o he C = O band om 1666 cm o 1 o 1627 cm−1, and he appea ance o he ela i e in ensi y o he C-H band a 2360 cm−1 (Fig. 3b). 4.2 In luence o di e en expe imen al pa ame e s on hg (II) e en ion by FCF To es he iabili y o he FCF as a Hg (II) adso ben , a ce - i ied Hg (II) s anda d o 1000 mg/L was used, om which a s anda d solu ion (1.0 mg/L) was p epa ed o e alua e he in luence o di e en ope a ing pa ame e s on he FCF (con- ac ime, adso ben dose, agi a ion, empe a u e and pH). Mo eo e , a ia ions in he ini ial Hg (II) concen a ion (10, 20, 30, 40, 60, 80, and 100 mg/L) we e s udied o es ablish he op imal wo king condi ions. The adso p ion pe cen age was calcula ed using Eq. (1). a omic a io be ween O: C equal o 46:54 and a s ong signal a ound 0.4 eV co esponding o C. 4.1.2 In a ed spec oscopy (FTIR) The un ea ed cabuya ibe (CF) displayed s ong FTIR bands a 1029 cm−1, 1322 cm−1, 1666 cm−1, 2920 cm−1, and 3332 cm−1 (Fig. 3a). The 1029 cm−1 bands a e cha ac e is ic o na u al cellulosic ibe s and a e a ibu ed o he s e ch- ing o he p ima y alcohol (-C-O-H) [39]. The bands a 1322 cm−1 a e a ibu ed o he -C-O s e ching band and he p es- ence o an isop opyl g oup on he su ace. The bands a ound 2920 cm−1 a e associa ed wi h asymme ical and symme i- cal me hyl and me hylene s e ching g oups. The band a 1666 cm−1 co esponds o he C = O es e , while he bands a ound 3332 cm−1 a e a ibu ed o he di e en s e ching modes o he O-H g oup [38]. A e exposu e o NaOH, he FTIR spec um o he ibe showed some changes, including Fig. 2 (a) SEM– EDS FCF analyzed a ea, (b) SEM– EDS FCF spec um Fig. 1 Mo phology o he cellulose su ace (FCF) (a) Inc ease o 800 × (20 μm) and (b) inc ease o 370 × (50 μm) 1 3 Page 5 o 27 40 Adso p ion (2025) 31:40 o Hg (II) unde hese condi ions we e 86.61% and 92.32%, espec i ely. I is also e iden ha wi hin he i s 5 min, he adso p ion exceeded 65%, con i ming ha FCF has se e al ac i e si es wi h adequa e a ini y be ween he OH g oups o Hg (II), allowing immedia e in e ac ion a e con ac , which esul s in e ec i e adso p ion [40]. 4.2.2 E ec o adso ben dose This s udy in es iga ed he e ec o adso ben dose on he emo al o Hg (II) ions om aqueous solu ions (Fig. 5), e ealing ha he adso p ion p ocess is closely ela ed o he a ailabili y o ac i e si es o con aminan in e ac ion [41]. Using di e en amoun s o adso ben (0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 g) a a concen a ion o 1.0 mg/L, unde agi a ion o 120 min a 150 pm and a cons an empe a u e Adso p ion (%) = Ci −C Ci ×100% (1) Whe e Ci (µg/L) and C (µg/L) ep esen he me al concen- a ions in he p epa ed Hg (II) solu ion be o e and a e adso p ion, espec i ely. 4.2.1 E ec o con ac ime The e ec o con ac ime on he FCF was in es iga ed wi h 0.5 and 1.0 g o FCF samples in 100 mL o a solu ion o 1.0 mg/L o Hg (II), agi a ion (150 pm), ime ange (5–240 min), and a cons an empe a u e o 25 °C. Figu e 4 shows ha he adso p ion e iciency o Hg (II) inc eased o e ime om 5 o 120 min, ollowed by sligh deso p ion a 240 min. The e o e, 120 min was chosen as he op imal con ac ime o he subsequen expe imen s. The maximum adso p ions Fig. 3 FTIR spec a o cabuya ibe spec a (a) d ied be o e exposu e o sodium hyd oxide (NaOH), (b) a e exposu e o sodium hyd oxide (NaOH) ( ime 4 h and empe a u e 40 °C 1 3 40 Page 6 o 27 Adso p ion (2025) 31:40 4.2.4 E ec o solu ion pH The pH o a solu ion can signi ican ly a ec s he adso p- ion p ocess o me al ions on adso ben s. This is because he pH can a ec bo h he me al species in he solu ion and he su ace cha ac e is ics o he adso ben s. Fo ins ance, i can in luence he dissocia ion o unc ional g oups and gene a- ion o cha ges on he su ace [44]. The poin o ze o cha ge (PZC) o FCF (Fig. 7) is a c ucial pa ame e in he adso p- ion p ocess and was de e mined o be 2.90. This alue has signi ican implica ions o Hg (II) emo al. When he solu- ion pH is g ea e han he pH PZC, he FCF su ace acqui es a ne nega i e cha ge, which inc eases he adso p ion capac- i y by p omo ing elec os a ic in e ac ions be ween ca ionic Hg (II) and elec on- ich su ace si es. Con e sely, when he pH is lowe han he pH PZC, he adso ben su ace exhib- i s a ne posi i e cha ge, gene a ing epulsi e o ces ha , in heo y, should educe Hg (II) adso p ion [4, 45]. This e ec is e lec ed in he expe imen al esul s (Fig. 8), whe e adso p ion inc eases signi ican ly a pH condi ions abo e 2.9, eaching a maximum in he pH ange o 5. o 25 °C, i was obse ed ha he pe cen age o Hg (II) ion emo al inc eased signi ican ly om 48.96 o 92.32% as he adso ben dose ose om 0.2 g o 1.0 g. Beyond his poin , he emo al e iciency emained nea ly cons an , iden i y- ing 1.0 g as he op imal dose. This s abiliza ion could be a ibu ed o sys em sa u a ion o adso ben agg ega ion, phenomena ha educe he speci ic adso p ion e iciency despi e he inc eased amoun o adso ben [42]. 4.2.3 In luence o empe a u e Tempe a u e is an addi ional ac o ha a ec s he so p ion p ocess. In his s udy, equilib ium da a in he empe a u e anges o 25, 35, and 40 °C we e used, using a dose o 1.0 g o adso ben and an analy e concen a ion o 1.0 mg/L. Figu e 6 shows how he adso p ion capaci y o Hg ions inc eased p og essi ely wi h inc easing empe a u e, wi h a maximum adso p ion o 96.81%. This could be explained by he ac ha a highe empe a u es, he e is be e in e - ac ion be ween he Hg ions and he ac i e g oups o he FCF [43]. Fig. 4 In luence o con ac ime on Hg (II) adso p ion. Tes condi ions: 1.0 mg/L; 150 pm; T=25 °C; V = 100 mL, mAdso ben = 0.5 g and 1.0 g 1 3 Page 7 o 27 40 Adso p ion (2025) 31:40 4.2.5 E ec o ini ial hg (II) concen a ion The impac o he ini ial concen a ion o Hg (II) on he pe - cen age o Hg (II) adso p ion by FCF in he aqueous solu ion was in es iga ed o iden i y he possible sa u a ion o FCF. The ini ial concen a ion o Hg (II) (10, 20, 30, 40, 60, 80, and 100 mg/L) was a ied while main aining o he pa am- e e s such as an adso ben dose o 1.00 g, agi a ion speed o 150 pm, con ac ime o 120 min, no pH adjus men , and a cons an empe a u e o 25 °C. The esul s ob ained o he e ec o he ini ial concen a ion o Hg (II) on he adso p- ion o Hg (II) ions is shown in Fig. 9. 4.2.6 E ec o agi a ion Figu e 10 shows he Hg (II) ion adso p ion capaci y o FCF when agi a ed a 150 pm wi hou agi a ion. The assay was pe o med a an ini ial concen a ion o 10 mg/L, main ain- ing pa ame e s such as an adso ben dose o 1.0 g, con ac The s udy e ealed ha he maximum adso p ion o Hg (II) (Fig. 8) was achie ed a a pH o 5, while he bes adso p ion esul s wi h FCF we e obse ed a pH le els o 3, 5, and 7, wi h adso p ion e iciencies o 90%, 92%, and 89%, espec i ely. These esul s indica e ha FCF can e ec- i ely abso b Hg (II) a pH alues close o neu al, which is an ad an age when dealing wi h eal e luen s in mining a eas [46]. On he o he hand, he lowes eco ded adso p- ion, 67%, occu ed a a pH o 1, which is a ibu ed o he acidic na u e o he medium. Unde hese condi ions, he ac i e g oups o he adso ben may unde go pa ial p o on- a ion, limi ing i s adso p ion capaci y, in addi ion o com- pe i ion be ween H(I) and Hg (II) ions o he ac i e si es o FCF [47]. A a pH o 9, a dec ease in Hg adso p ion was obse ed, likely due o he p esence o a ious Hg species in wa e , such as Hg (OH), Hg (OH)2, and Hg (II), which p omo e he o ma ion o Hg (II) hyd oxide complexes and educe adso p ion e iciency [48]. Mo eo e , he p esence o high concen a ions o Na+ ions could compe e wi h Hg (II) ions o he adso p ion si es on he FCF su ace [49]. Fig. 5 Dosing o adso ben mass in he Hg (II) adso p ion expe imen s. Tes condi ions: 1.0 mg/L; 150 pm; T=25 °C; V= 100 mL, =120 min 1 3 40 Page 8 o 27 Adso p ion (2025) 31:40 he su ace becomes oughe , leading o a pa ial block- age o some po es and educing he a ailable su ace a ea, he eby dec easing he adso p ion capaci y [51]. Figu e 11b and d p esen he esul s o he EDS analysis ollowing he adso p ion o Hg a concen a ions o 1 mg/L and 10 mg/L, espec i ely. In he wo compa a i e analyses, signi ican di e ences we e obse ed in he elemen al composi ion. In he i s case, Hg II was no de ec ed, likely due o wo k- ing wi h an ini ial concen a ion o only 1 mg/L o Hg (II) o he adso p ion p ocess wi h FCF. This esul ed in aces ha we e oo small o be de ec ed by he limi ed sensi i i y o he analysis. In con as , in he second analysis, minimal aces o Hg (II) we e iden i ied (0.01% by mass and 0.02% by a oms), as a highe ini ial concen a ion o 10 mg/L o Hg (II) was used o he adso p ion p ocess. This inc ease may ha e imp o ed he sensi i i y o he analysis. Rega d- ing ca bon (C) and oxygen (O), bo h elemen s p edomina ed a he a omic le el in he analyses; howe e , hei mass con- ibu ion was g ea e in he i s case (8.48% and 10.45%, espec i ely, compa ed o 2.50% and 2.21% in he second). These di e ences could be a ibu ed o a la ge su ace ime o 120 min, pH o 5, and a cons an empe a u e o 25 °C. I can be ound ha he e iciency in he emo al o Hg ions is highe when wo king wi h agi a ion eaching an adso p ion o 91.84%, while adso p ion wi hou agi a ion eaches 87.68%. F om he esul s ob ained, i is e iden ha agi a ion is a c i ical aspec o be conside ed o imp o - ing adso p ion, because i allows he adso ba e molecules o ha e g ea e con ac wi h he adso ben , gua an eeing g ea e homogenei y in all emp y si es on he su ace o he adso ben [50]. 4.2.7 SEM and EDS a e he adso p ion p ocess Figu e 11 shows he su ace mo phology FCF a e he adso p ion o Hg (II), obse ed a a magni ica ion o 300X (Fig. 11a and c). Compa ing his mo phology wi h ha o he ini ial adso ben , p esen ed in Fig. 1a and b o Sec . 4.1.1, a signi ican change can be obse ed. P io o adso p ion, he su ace o he adso ben is clean and homo- geneous, p o iding nume ous ac i e si es o in e ac ion wi h con aminan s. Howe e , a e he adso p ion p ocess, Fig. 6 Adso p ion o Hg (II) on FCF a di e en empe a u es. Tes condi ions: 1.0 mg/L; 150 pm; mAdso ben = 1.0 g; V= 100 mL, =120 min 1 3 Page 9 o 27 40 Adso p ion (2025) 31:40 Ce is he concen a ion o he me al a equilib ium (mg/L) and Co is he ini ial concen a ion o Hg (II) (mg/L). The alues o he s anda d changes in en halpy (ΔH0) and en opy (ΔS0) we e calcula ed om he slope and in e cep o he ln Kc e sus 1/T plo . Table 4 shows he he mody- namic pa ame e s o he adso p ion o Hg (II) ions on he FCF. O he au ho s ha e sugges ed s udying he s anda d change in he Gibbs ee ene gy using he ollowing equa- ions [77]: K0 e= (1000 •K L •M)•1mol/L γ (14) ∆G 0=−RTlnK0 e (15) whe e KL (L/mg) is he Langmui adso p ion cons an , which is ela ed o he p ope ies o he adso ben , he adso ba e, and he empe a u e. Whe e M ep esen s he 4.5 The modynamic s udy Se e al esea che s ha e analyzed he he modynamic p op- e ies o cellulose-based adso ben s wi h espec o Hg (II). Some s udies ha e desc ibed he endo he mic na u e o Hg (II) adso p ion by cellulose-based adso ben ma e ials [75]. The he modynamic pa ame e s can be s udied wi h he Gibbs F ee Ene gy s anda d change using he ollowing equa ion: ∆G 0=−RTlnKc (12) whe e R is he uni e sal gas cons an , T is he absolu e em- pe a u e (K), and Kc is he adso p ion equilib ium cons an [76]: Kc = Co −Ce Ce (13) Fig. 13 Langmui iso he m plo s o he adso p ion o Hg (II) on FCF 1 3 40 Page 16 o 27 Adso p ion (2025) 31:40 Fig. 15 Dubinin-Radushke ich iso he m plo s o he adso p ion o Hg (II) on FCF Fig. 14 Hg (II) adso p ion iso he ms on FCF acco ding o he Temkin model 1 3 Page 17 o 27 40 Adso p ion (2025) 31:40 concen a ion du ing deso p ion. The deso p ion pe cen - ages, deno ed as D, we e calcula ed om he adso p ion and deso p ion da a using he ollowing Equa ion [81]: %D= C des Cads (17) whe e Cdes (mg/g) is he amoun o me al deso bed by (HCl and HNO3) and Cads (mg/g) is he amoun o me al adso bed by he solid. Figu e 19 shows ha he deso p ion p ocesses we e incomple e when using 0.1 mol/L HCl and 0.1 mol/L HNO3 o e 8 h. The pe cen age o Hg deso bed using HNO3 (31%) was highe han ha deso bed using HCl (21%). The mos ly i e e sible na u e o adso p ion can be a ibu ed o speci ic in e ac ions a high-ene gy si es in FCF [82]. This obse - a ion is consis en wi h he pseudo-second-o de model, which p o ed o be he mos sui able o ep esen ing he expe imen al Hg (II) adso p ion alues in he FCF. This model is ypically associa ed wi h chemical adso p ion p ocesses. 4.7 Reusabili y Reusabili y is a c ucial componen o good adso ben s, in e ms o s abili y and cos -e ec i eness o p ac ical appli- ca ions. Deso p ion es s we e pe o med using 0.1 mol/L HCl and 0.1 mol/L HNO3 as an eluen o e alua e he egen- e a ion po en ial o FCF and i s eusabili y as adso ben s o he emo al o Hg (II) ions. The esul s a e shown in Table 6. The esul s o he eusabili y s udy showed ha deso p- ion esul ed in minimal loss in he adso p ion capaci y o he cellulosic ibe . The pe cen age o Hg (II) ion emo ed dec eased as he numbe o eusabili y cycles inc eased. The pe cen age o Hg (II) ion emo al using HNO3 dec eased om 92 o 74% (18% loss), whe eas when HCl was used, i dec eased om 90 o 62% in bo h cases a e h ee adso p- ion/deso p ion cycles. This dec ease in he pe cen age o adso p ion can be explained by epe i i e adso p ion/deso p- ion p ocesses ha cause deple ion o ac i e si es [83]. How- e e , hese indings indica e ha he unc ionalized ibe can egene a e e en a e being epea edly used o Hg (II) ions, molecula weigh o he adso ba e, γ is he coe icien o ac i i y (dimensionless), assumed o be 1.0, and Ke 0 is he dimensionless he modynamic equilib ium cons an . ∆G (kJ/mol) is he Gibbs ee ene gy change and R is he gas cons an (8.314 J/mol/K). Table 5 summa izes his me hod. This can be seen in Tables 4 and 5 all ΔG° alues we e nega i e, demons a ing ha he adso p ion o Hg (II) in FCF is he modynamically iable and spon aneous in na u e. In addi ion, ΔG° alues below 40 kJmol−1 indica e ha he p ocess o Hg (II) adso p ion in FCF should no be conside ed a chemically pu e mechanism, bu also ha i occu s by a physical mechanism [78]. Finally, he posi i e alues o ΔH° and ΔS° o Hg (II) adso p ion indica e he endo he mic na u e o his p ocess and a end o inc easing andomness in he equilib ium be ween he adso ben and he adso bed me al [79]. 4.6 Deso p ion Analysis To ully cha ac e ize he sys em in his s udy, he deso p- ion p ocess mus also be analyzed. The amoun o e ained me al (mg Hg (II) pe g FCF) was calcula ed om he di e - ence be ween he amoun adso bed and deso bed, acco ding o he ollowing Equa ion [80]: C =Cads −Cdes (16) whe e C (mg/g) and Cads (mg/g) a e he amoun s e ained and adso bed, espec i ely, and Cdes (mg/g) is he equilib ium Table 1 Iso he mal pa ame e s o he Langmui and F eundlich models o hg (II) adso p ion on FCF a 25 °C Langmui Model F eundlich model qm (mg/g) KL (L/mg) R2K (mg/g) 1/n (L/mg) R2 8.29 0.146 0.99 0.87 0.72 0.95 Temkin Model Dubinin–Radushke ich Model AT(L/g) bT(kJ/mol) R2qm (mg/g) B E(kJ/mol) R2 5.07 0.21 0.88 3.40 9,00E-05 105.41 0,82 Sepa a ion Fac o Concen a ion (mg/L) 10 20 30 40 60 80 100 RL 0.40 0.25 0.18 0.14 0.10 0.07 0.06 Table 2 Compa ison o he maximum so p ion capaci y o FCF (qm) wi h hose epo ed in he li e a u e o ano he so ben cellulose Me al Adso ben T (°C) qm (mg/g) Re e - ence Hg (II) Diaminoguanidine unc ion- alized cellulose 25 °C 55 mg/g [64] Hg (II) Thiophene unc ionalized cellulose 25 °C 109.7 mg/g [65] Hg (II) Guanyl-modi ied cellulose 25 °C 49 mg/g [66] Hg (II) Modi ied hemp ibe s 30 °C 57 mg/g [45] Hg (II) Flax ibe s 25 °C 5.2 mg/g [25] Hg (II) FCF (Aga e Ame icana ASPARAGACEAE) 25 °C 8.29 mg/g This s udy 1 3 40 Page 18 o 27 Adso p ion (2025) 31:40 Fig. 16 Pseudo i s -o de kine ic model o Hg (II) emo al by FCF 1 3 Page 19 o 27 40 Adso p ion (2025) 31:40 las Nie es Bene icia ion Plan was ound. The collec ed samples had pH alues close o neu al, anging om 6.3 o 6.9. The conduc i i y alues a ied om 1157 µS/cm o 1463 µS/cm, exceeding he maximum accep able le el o 1000 µS/cm, indica ing an inc eased sal concen a ion. Alkalini y alues we e be ween 2.8 mg/L CaCO3 and 3.8 mg/L CaCO3, sugges ing dissolu ion o ocky ma e ial, and we e classi ied as low a below 75 mg/L CaCO3 [84]. P e-analysis o was ewa e samples om selec ed s a- ions e ealed Hg (II) concen a ions anging om 1.8 µg/L o 26.27µg/L. Physicochemical pa ame e s o he wa e samples a e lis ed in Table 7. To assess he e iciency o FCF in ield applica ions, eal samples om ou poin s we e mixed, and 10, 20, and 30 mg/L o Hg (II) we e added o o - i y he mining wa e wi h Hg (II) and o e alua e he c i ical adso p ion condi ions o FCF. The esul s in Fig. 21 dem- ons a e he high pe cen ages o Hg (II) elimina ion unde c i ical condi ions. A 10 mg/L, he expec ed adso p ion o 91% was achie ed; howe e , when 20 mg/L and 30 mg/L we e added, he FCF began o sa u a e wi h o he ions, such indica ing he eusabili y and s abili y po en ial o he FCF o Hg ion emo al by adso p ion. Addi ionally, hese indings showed ha HNO3- ea ed FCF we e mo e sui able han HCl- ea ed FCF o epea ed use. The di e ence be ween he ibe s a e acid ea men in e ms o eusabili y was possibly due o he s e ching band o he hyd oxyl (OH) g oup. The FTIR spec um (Fig. 20c) shows ha a e ea men wi h 0.10 mol/L HCl, he e is almos no p esence o (OH) g oups, p oducing losses o many FCF unc ionali ies. On he o he hand, when obse - ing he s e ch band a e ea men wi h 0.10 mol/L HNO3 (Fig. 20b), i was obse ed ha he (OH) g oups we e no signi ican ly educed, esul ing in be e eusabili y due o he g ea e p esence o ac i e si es, so ha hey in e ac in he adso p ion o Hg (II). 4.8 Holding capaci y in eal hg (II)-Fo i ied Wa e samples Samples we e collec ed om eal wa e sou ces whe e a i- sanal mining was e om he Za uma a ea o he Vi gen de Fig. 17 Pseudosecond-o de kine ic model o Hg (II) emo al by FCF 1 3 40 Page 20 o 27 Adso p ion (2025) 31:40 as Cu and Pb, dec easing he capaci y o emo e Hg (II), esul ing in adso p ion a es o 83% and 57%, espec i ely. 5 Summa y esul s This s udy analyzes he adso p ion o Hg (II) a concen a- ions anging om 1.0 mg/L o 100.0 mg/L, unde empe a- u es om 25 o 45 °C and pH a ying om 1 o 9. Adso ben doses be ween 0.2 and 1.2 g we e employed, and es s we e conduc ed o e ime in e als om 5 o 120 min, all a a s i ing speed o 150 pm. The unc ionaliza ion o ique ibe was pe o med h ough NaOH ea men o enhance i s adso p ion capaci y. The unc ionalized ibe (FCF) was cha ac e ized using SEM, EDS, and FTIR. FTIR analysis e ealed bands a 1029 cm⁻¹, 1322 cm⁻¹, 1666 cm⁻¹, 2920 Table 3 Kine ic Model Pa ame e s Pseudo 1s o de model 10 mg/L 20 mg/L 30 mg/L 40 mg/L qe (mg/g) 0.124 0.092 0.187 0.142 k1(min−1) 0.0071 0.0093 0.0204 0.0242 R20.83 0.96 0.84 0.90 Pseudo 2nd o de model 10 mg/L 20 mg/L 30 mg/L 40 mg/L qe (mg/g) 0.91 1.82 2.69 5.56 K2mg/(g.min) 0.42 1.01 0.244 0.249 R20.99 0.99 0.99 0.99 Elo ich model 10 mg/L 20 mg/L 30 mg/L 40 mg/L β(mg/g) 28.25 36.23 21.88 21.79 αmg/(g.min) 1.82E + 07 3.64E + 24 2.85E + 21 9.53E + 29 R20.97 0.93 0.82 0.92 Table 4 The modynamic Pa ame e s o Hg (II) Ion Adso p ion in FCF T (K) Ln Kc ∆G0 (kJ/mol) ΔH0 (kJ/mol) ΔS0 (J/mol·K) 298 2.487 −6.16 36.29 141.98 308 2.784 −7.12 318 3.412 −9.02 Table 5 Gibbs ee ene gy o adso p ion o Hg (II) ions in FCF in ela- ion o Langmui adso p ion cons an T (K) Ln K e 0∆G0 (kJ/mol) 298 5.11 − 12.66 Fig. 18 Elo ich kine ic model o Hg (II) emo al by FCF 1 3 Page 21 o 27 40 Adso p ion (2025) 31:40 FCF was a o ed when pH app oached 5. FCF’s adso p ion capaci y inc eased as empe a u e ose o 25, 35, and 45 °C, eaching alues o 92%, 94%, and 97%, espec i ely. Agi a- ion p o ed no o be a highly ele an ac o , achie ing 92% adso p ion wi h agi a ion and 89% wi hou i . Fo Hg (II) concen a ions o 10, 20, 30, and 40 mg/L, FCF adso p ion emained s able a a ound 90%, indica ing ha FCF main- ains i s adso p ion wi hou sa u a ion up o 40 mg/L. The highes me cu y adso p ion alue was 97% wi h 1.0 mg/L o me cu y. This esul was achie ed using FCF a pH 5, 240 min con ac ime, 150 pm, and 45 °C. Langmui , F eun- dlich, Temkin, and D-R iso he ms we e used o desc ibe Hg adso p ion beha io on FCF. Equilib ium da a esul s showed be e i ing o he Langmui iso he m, eaching a maximum adso p ion capaci y o 8.29 mg/g. This beha io sugges s a homogeneous dis ibu ion o ac i e si es on he adso ben su ace and he p edominance o chemical in e - ac ions du ing he adso p ion p ocess. Adso p ion kine ics we e e alua ed using pseudo- i s -o de , pseudo-second- o de , and Elo ich models. Expe imen al da a showed be e i ing o he pseudo-second-o de model, cha ac e ized by cm⁻¹, 2360 cm⁻¹, and 3370 cm⁻¹. No ably signi ican is he band a 3370 cm⁻¹, a ibu ed o di e en OH g oup s e ch- ing modes. The abundance o hyd oxyl g oups (OH) in he ibe s uc u e sugges s enhanced adso p ion capaci y. To analyze he iabili y o Hg (II) adso p ion wi h FCF, pa am- e e s such as ime, concen a ion, pH, adso ben amoun , and empe a u e we e e alua ed. The equilib ium ime o me cu y e en ion was eached wi hin he i s 2 h, achie - ing a ema kable adso p ion pe cen age o 92%. Rega ding he adso ben amoun e ec , 1.0 g o FCF was de e mined as he op imal quan i y o maximize adso p ion. Inc easing he adso ben mass abo e his alue did no esul in signi ican imp o emen in adso p ion capaci y. Me cu y adso p ion on Table 6 Reu iliza ion o unc ionalized (FCF) o Hg (II) Reusabili y Cycles Hg (II) Reco e y (%) T ea men HNO3 T ea men HCl 1 92 90 2 81 76 3 74 62 Fig. 19 Pe cen age o Hg (II) deso p ion using HCl and HNO3. Tes condi ions: 150 pm; m FCF(Hg (II)) = 1.0 g; V = 100 mL, = 8 h, = 25 °C 1 3 40 Page 22 o 27 Adso p ion (2025) 31:40 achie ing h ee e ec i e euse cycles wi h HNO₃ and HCl, wi h e iciencies o 74% and 62%, espec i ely. The ob ained esul s demons a e ha FCF is e ec i e o Hg (II) emo al in bo h syn he ic aqueous solu ions and eal wa e s, posi ioning i as a iable and economical al e na i e o ea ing me cu y con amina ed wa e s. 6 Conclusions Expe imen ally, he syn he ic samples showed ha he ze o- cha ge poin o FCF was ela i ely low, indica ing a good abili y o adso b ca ions. The FCF wi h Hg (II) had an equi- lib ium ime o app oxima ely 120 min, wi h a maximum adso p ion pe cen age o 92%, and 1.0 g o adso ben and agi a ion a pH 5.0, unde s anda d condi ions. The maxi- mum adso p ion ob ained (qm) was 8.29 mg/g, which i ed he Langmui iso he m. Mo eo e , an inc ease in empe a- u e o 45 °C inc eased he adso p ion pe cen age o FCF, eaching 97% o Hg (II). The he modynamic pa ame e s a apid ini ial adso p ion a e. The modynamic pa ame e s con i med ha Hg (II) adso p ion on FCF is a spon aneous and endo he mic p ocess. The es ablished op imal condi- ions we e applied o eal wa e samples om he Vi gen de las Nie es P ocessing Plan , achie ing an adso p ion e iciency o 91% o Hg (II). The adso ben ’s egene a- ion capaci y was also e alua ed h ough deso p ion cycles, Table 7 Physicochemical pa ame e s and hea y me als p esen in eal wa e samples Vi gen de las Nie es Bene icia ion Plan Physicochemical Pa ame e s Uni M1 M2 M3 M4 Alkalini y mg/L 3.4 3.8 3.1 2.8 TDS mg/L 733.5 768.6 856.3 875.6 Conduc i i y µS/cm 1203 1157 1463 1225 pH 6.47 6.78 6.89 6.58 Tu bidi y NTU 1314 1236 1456 1025 Hea y me als Uni M1 M2 M3 M4 Me cu y (Hg (II)) µg/L 3.35 1.19 26.27 1.82 Lead (Pb) µg/L 143 3.50 - 473.3 Coppe (Cu) µg/L 2166.7 172.4 2083.26 845.6 Fig. 20 FTIR spec a o FCF (a) d ied be o e adso p ion (b) a e adso p ion and ea ed wi h ni ic acid (HNO3) (c) a e adso p ion and ea ed wi h hyd ochlo ic acid (HCl) 1 3 Page 23 o 27 40 Adso p ion (2025) 31:40 Decla a ions Compe ing in e es s The au ho s decla e no compe ing in e es s. Open Access This a icle is licensed unde a C ea i e Commons A ibu ion 4.0 In e na ional License, which pe mi s use, sha ing, adap a ion, dis ibu ion and ep oduc ion in any medium o o ma , as long as you gi e app op ia e c edi o he o iginal au ho (s) and he sou ce, p o ide a link o he C ea i e Commons licence, and indica e i changes we e made. The images o o he hi d pa y ma e ial in his a icle a e included in he a icle’s C ea i e Commons licence, unless indica ed o he wise in a c edi line o he ma e ial. I ma e ial is no included in he a icle’s C ea i e Commons licence and you in ended use is no pe mi ed by s a u o y egula ion o exceeds he pe mi ed use, you will need o ob ain pe mission di ec ly om he copy igh holde . To iew a copy o his licence, isi h p : / / c e a i e c o m m o n s . o g / l i c e n s e s / b y / 4 . 0 / . Re e ences 1. Uddin, M.K.: A Re iew on he Adso p ion o Hea y Me als by clay Mine als, wi h Special Focus on he pas Decade. 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