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Access to drinkable water is becoming more and more challenging due to worldwide pollution and the cost of water treatments. Water and wastewater treatment by adsorption on solid materials is usually cheap and effective in removing contaminants, yet classical adsorbents are not sustainable because they are derived from fossil fuels, and they can induce secondary pollution. Therefore, biological sorbents made of modern biomass are increasingly studied as promising alternatives. Indeed, such biosorbents utilize biological waste that would otherwise pollute water systems, and they promote the circular economy. Here we review biosorbents, magnetic sorbents, and other cost-effective sorbents with emphasis on preparation methods, adsorbents types, adsorption mechanisms, and regeneration of spent adsorbents. Biosorbents are prepared from a wide range of materials, including wood, bacteria, algae, herbaceous materials, agricultural waste, and animal waste. Commonly removed contaminants comprise dyes, heavy metals, radionuclides, pharmaceuticals, and personal care products. Preparation methods include coprecipitation, thermal decomposition, microwave irradiation, chemical reduction, micro-emulsion, and arc discharge. Adsorbents can be classified into activated carbon, biochar, lignocellulosic waste, clays, zeolites, peat, and humic soils. We detail adsorption isotherms and kinetics. Regeneration methods comprise thermal and chemical regeneration and supercritical fluid desorption. We also discuss exhausted adsorbent management and disposal. We found that agro-waste biosorbents can remove up to 68–100% of dyes, while wooden, herbaceous, bacterial, and marine-based biosorbents can remove up to 55–99% of heavy metals. Animal waste-based biosorbents can remove 1–99% of heavy metals. The average removal efficiency of modified biosorbents is around 90–95%, but some treatments, such as cross-linked beads, may negatively affect their efficiency.

The adsorption potential of raw pomegranate peel powder (PMPP) for lead (Pb) ions was investigated via batch mode at varying initial adsorbate concentration, contact time, and adsorbent concentration. The PMPP was extensively characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersion X-ray (EDX), thermogravimetry (TG), and differential scanning calorimetry (DSC) analyses. The instrumental characterization results confirmed the presence of important functional groups and surface texture/morphology that played key roles during the lead ion adsorption. Description of the experimental equilibrium data by nonlinear Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models was elaborately presented in the study. The experimental kinetic data were fitted to the Pseudo-first-order, Pseudo-second-order, Intra-particle diffusion, and Elovich models. The Temkin model satisfactorily predicted the isotherm data. Meanwhile, the intra-particle diffusion model was best at predicting the kinetic data at adsorbate concentration of 150 mg/L, while the Elovich model emerged as the best fit at 300 mg/L concentration. This study shows that lead ions could be efficiently removed using raw pomegranate peel powder.

Acid mine drainage (AMD) is a multi-factor pollution formed from complex chemical, physical, and biological interactions that takes place under ambient conditions in abandoned and active mines. Over the years, researchers have been investigating ways to mitigate its potential impact on the environment through various treatment technologies. The aim of this review was to critically analyze the broad spectrum of treatment methods that have been engaged in published literature on the remediation of AMDs. Adsorption treatment using zeolites, fly ash, biochar activated carbon, clay-based minerals and biomass-based adsorbents was discussed. Given an appropriate choice of adsorbent, ions in AMD can be reduced between 50% and 99%. Membrane separation processes like nanofiltration, reverse osmosis and hybrid systems were discovered to be more effective than adsorption and can effect over 90% rejection at optimized conditions. Biological processes showed a far wider range of performance amongst all treatment types due to the selectivity in performance of the different micro-organisms used although Advanced Oxidation Process (AOPs) have been shown to achieve>80% ions removal. In all biological processes studied ranging from wetlands to bioreactors, algal bioreactors seemed the most effective in this domain. Most of these treatment technologies are corrective while preventive techniques can be explored to prevent the production of AMD. Despite the positive outcomes of the different types of treatment, they have associated technical issues. It is recommended that more preventive techniques be explored to reduce the production of AMD. The review discussed how AMD treatment would affect environmental protection and water resource management.

Acetaminophen (ACT) is an effective and widely available analgesic and antipyretic used in medical practice. It can get into water from veterinary use, medical waste and pharmaceutical effluents. The aim of this review was to elaborate on the recent progress on ACT adsorption from water, present the findings in a structured written report and identify interesting new foundations for further work. ZnAl/biochar had the highest potential of removing ACT and can adsorb more than its weight of the pollutant ( q max > 1000 mg/g). The Langmuir and Freundlich isotherm models and the pseudo-second-order kinetics model were best-fits in most cases (usually at R2 > 0.99 threshold). It was observed that the key mechanisms of ACT uptake are π-π interactions, hydrogen bonds and electrostatic interaction. For most of the adsorbents, a >30% ACT removal efficiency was achievable after the 4 cycles. Effects as salting-out, electrostatic screening, and accumulation of moieties at sorbent-sorbate interfaces due to the competitive adsorption of ions and co-pollutants are profound in the uptake of ACT from aqueous solutions. Future perspectives were discussed in the area of process costing, adsorbent regeneration, mechanistic investigations and fixed-bed column adsorption.

A novel biosorbent (‘Manna_COOH’) was synthesized via dual reaction stages of direct carbonylation of hydroxyl groups of richly cellulosic manna root powder and subsequent esterification of the resultant anhydride analogue into an ester of high carboxyl content. Both the biosorbent precursor and the 2,3-dihydroxybutanedioic acid sustain complementary features that ensured their efficient complexation. The biosorbent depicted a carboxyl content of 412.36 m.eq -COOH/100 g sample and was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The study further evaluated the cobalt ion adsorption capacity of the synthesized ‘Manna_COOH’ under the effect of some process variable via batch mode. The Freundlich and pseudo-second-order models emerged as the best fit for the equilibrium and kinetic data, respectively. The rich oxygen-based surface functional groups entrenched on the ‘Manna_COOH’ sequel to its functionalization played a major role in making it a promising biosorbent for aqueous Co (II) uptake.

To entrench heavy metal chelation functional groups, native corn starch was grafted with acrylonitrile and subsequently hydrolyzed (using sodium hydroxide) to produce chemically crosslinked superabsorbent hydrogels (SAHs) of three-dimensional hydrophilic polymeric networks. SAHs demonstrated fast swelling and superabsorbent properties, with a swelling capacity of 612 g water/g SAHs. Due to the usefulness of equilibrium and kinetic data for elucidating the nature of adsorbate-adsorbent interaction, the adsorption study was extensively modelled using selected nonlinear isotherm and kinetics models. The Toth and intraparticle diffusion models satisfactorily predicted the isotherm and kinetic data, respectively, while the dominance of the metal complexation mechanism was asserted in the study. Meanwhile, the metal ion uptake by SAHs occurred at a fast equilibration time of 20 min. Furthermore, the adsorbent’s instrumental characterization (scanning electron microscopy, SEM; Energy dispersion X-ray, EDX; X-ray diffraction, XRD and Fourier-transform infrared spectroscopy, FTIR) result confirmed that SAHs possesses the desired metal chelation properties. Thus, the potential application of the developed SAHs as biosorbent in the decontamination of the heavy metal-laden stream was explicitly demonstrated in the study.

The need for a viable and sustainable environment has triggered the increased preference for eco-friendly agro-based biosorbents to synthetic ones. In this study, a superabsorbent hydrogel (‘c-hydrogel’) synthesized from a renewable agro-based precursor via polyacrylonitrile (PAN) graft copolymerization and subsequent hydrolysis was utilized for aqueous lead [Pb(II)] uptake. The chemical structure (using Fourier transform infrared spectroscopy, FTIR equipment), surface morphology (using scanning electron microscopy, SEM equipment) and the physicochemical properties of the synthesized ‘c-hydrogel’ were investigated. Similarly, the effect of some process variables on the biosorbents’ adsorption capacity, as well as the process equilibrium and kinetics modelling, was also undertaken in the study. The isotherm data were best fitted to the Langmuir and Temkin model, with a maximum adsorption capacity of 264.37 mg/g and fast kinetics of 40 min at pH 5.0. Conversely, the kinetic data were well fitted to the pseudo-first-order model. The ‘c-hydrogel’ showed a high water absorbency of 550 g water/g ‘c-hydrogel’ and demonstrated effectiveness, as a renewable and eco-friendly biosorbent for the aqueous lead ion [Pb (II)] removal.

This work investigated the corrosion inhibition ability of T. conophorum leaf extract (TCLE) on aluminium in a 3 mol/L HCl medium using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The effect of four process variables (acid conc., inhibitor conc., corrosion time and temperature) on the inhibition efficiency was optimized using Response Surface Methodology (RSM) techniques. The Tafel plot reveals the effectiveness of TCLE act as a mixed-type inhibitor, with relatively high inhibition efficiency (>70%). The optimal inhibition efficiency was determined at acid conc: 1.5 mol/L, inhibitor conc: 0.04 g/L, corrosion time: 4.5 h and temperature: 303 K. Analysis of variance (ANOVA) result confirmed the fitting goodness of quadratic regression model, with a models’ probability (p values), Fischer’s F-value, and lack-of-fit values of 0.0001, 15.76 and 0.999, respectively. Hence the corrosion data were well described by the quadratic model, as it presented sufficient forecasting of the optimal inhibitory conditions.

An anion exchanger (‘Cell-AE’) was prepared by grafting acrylonitrile (AN) onto carbon cloth waste followed by subsequent modification with hydrazine hydrate and dimethyl sulfate. The effect of radiation dose and monomer concentration was investigated. The nitrate ( $${\text{NO}}_{3}^{ - }$$ ) and phosphate ( $${\text{PO}}_{{{4}}}^{{{{3}} - }}$$ ) sorption potentials of the ‘Cell-AE’ was evaluated via batch mode. The ‘Cell-AE’ showed a higher adsorption affinity towards $${\text{PO}}_{{{4}}}^{{{{3}} - }}$$ than $${\text{NO}}_{3}^{ - }$$ . Similarly, the $${\text{PO}}_{{{4}}}^{{{{3}} - }}$$ and $${\text{NO}}_{3}^{ - }$$ adsorption was described by Dubinin–Radushkevich (D-R) and Redlich-Peterson (R-P) models, respectively. The present study conclusively proffered a potential mitigation approach to carbon cloth waste management.

Efficacy of treated sodium alginate (TSA) and activated carbon fibre (ACF) for aqueous Pb(II) uptake was comparatively investigated. By employing FTIR, SEM, EDX, XRD, point of zero charges and surface area measurements, the available functional groups, morphology, crystallinity, surface charge and surface areas of both adsorbents were respectively elucidated. The Pb(II) uptake performance of both adsorbents was also studied via batch mode at varied process conditions. The experimental isotherm and kinetic data for both adsorbents were best fitted to nonlinear forms of Langmuir and pseudo-first-order models, respectively. Similarly, intraparticle diffusion was the sole controlling mechanism. Despite the huge variation in the surface area, TSA (7.8 m2/g) with high carboxyl content (395.6 meq-COOH/100 g of sample) performed better by all standards than the ACF (975 m2/g). This finding showed that although the surface area of a given adsorbent is a key indicator of its adsorptive performance, the inherent surface functional groups play a superior role. The experimentally derived maximum adsorption capacities of 221.25 mg/g (for TSA) and 183.34 mg/g (for ACF) were recorded at an equilibrium time of 30 min and 45 min, respectively. Therefore, TSA and ACF demonstrated effectiveness for aqueous Pb (II) sequestration.

The study involved the synthesis of a novel adsorbent via the direct carbonylation of butane-1,4-dioic acid impregnated Alhagi root powder to its acid anhydride analogue and the subsequent esterification of the highly cellulosic plant material by the anhydride to an ester of high carboxyl content. The high carboxyl content of the synthesized adsorbent was recorded as 451.76 m.eq –COOH/100 g sample. The adsorbent was effectively characterized using Scanning electron microscopy, Energy dispersion X-ray, and Fourier-transform infrared spectroscopy, as well as utilized for aqueous cobalt ion sequestration. Similarly, the effect of the process variable on the carboxyl content and adsorption capacity of ‘ATAG’ was elucidated. The Dubinin–Radushkevich model satisfactorily predicted the isotherm data. Meanwhile, the intraparticle diffusion model was best at predicting the kinetic data at adsorbate concentration of 300 and 450 mg/L, while the pseudo-first-order model emerged as the best fit at 600 mg/L concentration. The maximum adsorption capacity of 188.67 mg/g was recorded at optimum adsorption conditions (pH 6.0, 60 min, and 30 °C), and the adsorption mechanism was also proposed. The abundant surface oxygenous functional groups on ‘ATAG’ positively influenced its adsorption capacity; thus, making it a promising biosorbent for aqueous Co (II) uptake.

N-[2-(methylamino)ethyl] ethane-1,2-diaminated acrylic fibre (DAAF) derived adsorbent was prepared by the reaction of acrylic fibre with bis(2-aminoethyl)amine. Fourier transform infrared spectroscopy and scanning electron microscopy were employed for elucidating the surface functional groups and morphology of DAAF, respectively. The influence of several process variables on Hg(II) adsorption was also evaluated. Equilibrium and kinetic studies were conducted using a range of two-parameter models via nonlinear regression methods. Langmuir and pseudo-second-order models emerged the best fit for isotherm and kinetic modelling, respectively. The intraparticle diffusion studies indicate that occurrence of an adsorption process, with multi-mechanistic effect. Similarly, the maximum adsorption capacity (qmax) of 627.5 mg g−1 was recorded in the study at pH 5.0, 30 °C and 15–30 min. The short equilibration time recorded in the study speaks volume of the potential application of DAAF in large-scale Hg(II) adsorption systems.

Starch is an abundant natural and renewable carbohydrate polymer, with cation sorption deficiency due to its high crystallinity and amylose content which causes substantive mass transfer resistance during adsorption. Therefore, the present study synthesized polyacrylonitrile grafted starch (graft-starch) that was subjected to heat treatment and saponification reaction to facilitate a partial transformation of the available amide groups (due to copolymer grafting) into carboxylate groups. The reactions afforded the desired polyacrylonitrile-grafted starch hydrogel (‘Poly-g-Hyd’) which was further utilized for zinc ion uptake. It was observed that the polar nitrile (CN) groups of the grafted polyacrylonitrile substantially improved the ‘Poly-g-Hyd’ water absorption capacity and cation binding interaction, as well as entrenched stable network chains that are insoluble in water. The water absorption and zinc ion sorption capacities of 490 g water/g ‘Poly-g-Hyd’ and 508.85 mg/g, were respectively recorded. Furthermore, the optimum adsorption conditions were established at pH 5.0, 20 min and 0.3 g/L, while the Freundlich and pseudo-second-order models provided the best fit to the isotherm and kinetic data, respectively. The study, therefore, demonstrated the effectiveness of ‘Poly-g-Hyd’ in the uptake of aqueous zinc ions.

In this study, naturally heated clay (NHC) was complexed with synthesized ionic liquid (1-ethyl-3-methyl imidazolium bromide solution (EMIB)) to form NHC/EMIB composite. The effectiveness of NHC/EMIB composite in comparison with naturally heated clay (NHC) as an eco-friendly adsorbent for dephenolation of petroleum effluent was investigated. The adsorbents were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. Batch mode experiments were conducted to ascertain the effect of process variables on adsorption. Removal efficiencies of 81.70% and 91.7% were obtained for NHC and NHC/EMIB composite, respectively, at 25 min, 308 K, pH 4.0 and 150 µm. The linear and nonlinear isotherm data fitted best to the Langmuir model for both adsorbent, while the linear and nonlinear kinetic data fitted best to pseudo-second-order and pseudo-first-order models for both adsorbents. The estimated average thermodynamic parameters (ΔG0 = − 9.653 kJ/mol, ΔH0 = –28.295 kJ/mol and ΔS0 = –46.395 kJ/mol) revealed the feasibility, exothermic nature and spontaneity, respectively, of the studied adsorption system.

Bamboo-based lignin (LBM) was synthesized from a simulated effluent of modified textile manufacturing process for bamboo fabrics. The efficacy of LBM modified with Al3+ (Al-LBM) and Mn2+ (Mn-LBM) for the remediation of crystal violet dye polluted wastewater was evaluated. Instrumental characterization of the adsorbents via Fourier transform infrared spectroscopy and scanning electron microscopy was conducted. Probable process mechanisms were postulated. The Langmuir, Sip and Freundlich isotherms were the best fit model for LBM, Al-LBM and Mn-LBM, respectively. Among the interactively competing mechanisms (confirmed by k-value and intra-particle diffusion model), the pseudofirst-order kinetic model predominated. Optimum temperature and contact time were 343 K and 30 min, respectively. The adsorption process was (based on average data) spontaneous (∆G = − 1198.69 kJ mol−1), endothermic (ΔH = + 86.85 kJ mol−1) and efficient (+ 98.11%).

The intensification of urbanisation and industrial activities significantly exacerbates the distribution of toxic contaminations into the aqueous environment. Persistent organic pollutants (POPs) have received considerable attention in the past few decades because of their persistence, long-distance migration, potential bioaccumulation, latent toxicity for humans and wildlife. There is no doubt that POPs cause serious effects on the global ecosystem. Therefore, it is necessary to develop a simple, safe and sustainable approach to remove POPs from water bodies. Among other conventional techniques, the adsorption process has proven to be a more effective method for eliminating POPs and to a larger extent meet discharge regulations. Nanomaterials can effectively adsorb POPs from aqueous solutions. For most POPs, a70% adsorptive removal efficiency was achieved. The major mechanisms for POPS uptake by nano-adsorbents includes electrostatic interaction, hydrophobic (van der Waals, π-π and electron donor-acceptor) interaction and hydrogen bonding. Nano-adsorbent can sustain a90% POPs adsorptive removal for about 3 cycles and reuseable for up to 10 cycles. Challenges around adsorbent ecotoxicity and safe disposal were also discussed. The present review evaluated recent research outcomes on nanomaterials that are employed to remove POPs in water systems.

Alhagi Graecorum (AG) is an invasive plant with a massive/robust root structure that can grow up to 12 feet into the ground. The present study exploited the rich cellulosic content in this ‘AG’ root for the synthesis of a novel biosorbent (‘MA’). This low-cost biosorbent, with high carboxyl content of 447.22 (m. eq /100 g sample) was utilised for aqueous zinc ion sequestration. The surface functional groups and textural characteristics required for an efficient heavy metal binding was identified on ‘MA’ using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Sip isotherm emerged as the model of best fit for equilibrium studies, hence, Zn (II) ion sorption onto ‘MA’ is believed to occur via a hybrid blend of homogenous monolayer and heterogeneous multilayer adsorption. Meanwhile, the Elovich (SNE = 1.0429), intraparticle diffusion (SNE = 1.0205) and pseudo-first-order (SNE = 1.0455) provided the best fitting for 200, 400 and 600 mg/L adsorption system, respectively. The maximum adsorption capacity of 188.67 mg/g was recorded at optimum adsorption conditions, with the predominance of the electrostatic and electron-donor-acceptor interaction mechanism. The abundant surface oxygenous functional groups on ‘MA’ positively influenced its adsorption capacity; thus, making it a promising biosorbent for aqueous Zn (II) uptake.

Despite their extensive and decade-long application in wastewater treatment, activated carbon remains one of the most viable adsorbents, with substantive practical application, due to their high pollutant binding capacity. In this study, commercially available activated charcoal was applied in the uptake of aqueous cadmium [Cd(II)] ion. The effect of some process variables on the Cd (II) uptake was investigated via batch mode. Furthermore, the adsorbents’ surface charge (pHPZC), surface morphology (using SEM) and available surface functional groups (using FTIR) were explained. The pH dependence of the present adsorption system was revealed, while the optimum pH was recorded at pH 5.0. Similarly, the Cd (II) uptake (mg/g) decreased with increasing adsorbent dosage due to possible active sites clogging, overcrowding and interference. Furthermore, the isothermal and kinetics analyses of the experimental data, which were aptly validated using the hybrid error model, respectively depicted the Langmuir isotherm and pseudo-second-order kinetic model as the best fit. A Langmuir adsorption capacity of 682.5 mg g−1 was also recorded in the study. Consequently, the present adsorption system was characterized by an equilibrium timeframe of industrial practicability; hence, the adsorbent was successfully applied for the aqueous Cd (II) uptake.

Ibuprofen (IBP) is a non-steroidal anti-inflammatory drug released into the environment through hospital and medical effluents, pharmaceutical wastewater and veterinary use. The aim of this paper is to review the empirical findings on the adsorption of IBP from aqueous media. A preliminary ecotoxicological assessment confirmed the environmental risk of IBP in the aqueous environment. Open literature works considered in this review were for the past decade (2010−2020). Carbon-based adsorbents are the best class of adsorbent for the uptake of IBP and the highest reported maximum adsorption capacity (qmax) for IBP is 496.1 mg/g by SWCNTs. The range of adsorption capacities for IBP uptake in this review is between 0.0496 and 496.1 mg/g. The mechanism of uptake is majorly by hydrophobic interactions, π – π stacking, hydrogen bonds, electrostatic interactions and dipole-dipole interaction. IBP uptake was best fit to a wide variety of isotherm models but was well suited to the pseudo-second order kinetics model. The thermodynamics of IBP uptake depends majorly on the nature of the adsorbent and desorption from the solid phase is based on an appropriate choice of the eluent. Knowledge gaps were observed in used adsorbent disposal and process improvement. In the future, interest would increase in scale-up, industrial applications and practical utilisation of the research findings which would help in sustainable water resource management.

This study focuses on the effectiveness of ionic liquid (1-ethyl-3-methyl imidazolium bromide, EMIB) and chemically modified (EMIB impregnated) clay (CMC) as adsorbents for dephenolation of petroleum effluent. Process equilibrium and kinetics (including mechanistic modeling) of the adsorption were investigated. The results showed uptake efficiencies of 91.7 and 85% for CMC and EMIB, respectively, at equilibrium time of 25 min. The linear and non-linear isotherm and kinetic models were best fitted to Langmuir and pseudo-second-order model for both adsorbents. The CMC and EMIB had their monolayer adsorption capacity equal to 3.487 and 0.989 mg/g, respectively. Seven mechanistic models were proposed, with mechanism IV and its corresponding model equation IV (shifting rate order model) emerging as the best fitting to the adsorption data. The thermodynamic studies showed that the process was physical (ΔH

Lignified isolate was successfully synthesized from simulated effluent of modified procedure for bio – ethanol production from elephant grass. The effectiveness of lignin isolate (EA); complexed with Al3+ (Al –EA) and Mn2+ (Mn – EA) for adsorbing aqueous crystal violet dye (CVD) was evaluated. The adsorbents were characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Removal efficiencies of Al k EA (98.42%) and Mn – EA (97.87%) were obtained at contact time of 30 min and 343 K. Kinetic study showed that Brouer – Weron – Sotolongo, Fractal – like mixed 1,2–order and Elovich models were the best three models in describing the adsorption kinetics of both adsorbent. Similarly, the predicted kinetic data were adjured statistically significant using F- test and student’s t-test. Application of mechanistic models suggests film diffusion as the rate controlling mechanism. The estimated average thermodynamic parameters (ΔG0 (−18.438 KJ/mol), ΔH0 (+27.968 KJ/mol) and ΔS0 (29.536 KJ/mol)) reveal that CVD adsorption onto Al – EA and Mn – EA was feasible, spontaneous and endothermic.

A lignin-based adsorbent ELGA, obtained from alkaline hydrolysis of elephant grass, was utilized for the removal of aqueous crystal violet dye (CVD). Batch mode experiments were carried out to study the effects of various process parameters on adsorption. ELGA was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The isotherm data fit into the Freundlich and Tempkin models for linear and nonlinear models, respectively; while kinetic data fit best to pseudo-first order (PFO) and Elovich models for linear and nonlinear kinetic models, intraparticle diffusion studies indicate that many mechanisms influenced the adsorption process. Gibb’s free energy and enthalpy changes of − 1198.57 and + 66.911 KJ mol−1, respectively, indicated spontaneous and endothermic process. An uptake efficiency (> 90%) recorded at an equilibrium time of 30 min shows that ELGA was a fast and effective adsorbent for the removal of aqueous CVD.

The Scopulariopsis brevicompactum fungal biomass (SFB) was applied as an adsorbent for the uptake of aqueous lead species via the dynamic sorption process. The adsorption capacity dependence on the solution pH, contact time, initial adsorbate concentration and adsorbent concentration was investigated via batch mode. According to the experimental findings, the adsorption capacity was favoured by an increase in all the aforementioned process variables except adsorbent concentration. The optimum adsorption capacity was recorded at pH 6.0, 120 min, and 0.2 g/L adsorbent concentration. The process isotherm was explained by the D -R model, with predominated physisorption (E = 0.069 kJ/mol), while the pseudo-second-order model explained the process kinetics. The characterization results confirmed the presence of several metal-binding functional groups on SFB. Furthermore, by applying the mass transfer factor model, the dependence of the lead ions adsorptive mass transfer on the film diffusion regime was established. Thus, the adsorptive performance of the SFB was demonstrated in the study.

The absence of relevant functional groups, especially the oxygen-based groups, have been reported to strongly limit the metal binding capacity of native cellulose. Therefore, this study successfully introduced substantive oxygenous functional groups (C˭O, –OH, C–O, etc.) onto microcrystalline cellulose via functionalization with 1,2,3,4-Butanetetracarboxylic acid. The synthesized adsorbent (‘FM-cell’) was further utilized for aqueous iron (II) ion uptake. The adsorbent’s instrumental characterization (scanning electron microscopy, SEM; Energy dispersion X-ray, EDX; X-ray diffraction, XRD and Fourier-transform infrared spectroscopy, FTIR) result confirmed the presence of the oxygen-based functional groups and their relative structural crystallinity. Similarly, the effect of the process variable on the ‘FM-cell’ adsorption capacity was elucidated via batch mode. The Dubinin-Radushkevich and intraparticle diffusion models satisfactorily predicted the isotherm and kinetic data, respectively. The sorption mechanism postulated strong adsorbent-adsorbate electrostatic interaction occasioned by the large coordination number of Fe (II) ions. Thus, the surface oxygenous functional groups abundance significantly enhanced the metal binding capacity of ‘FM-cell’.