Adsorption Of Toxic Metals Research Articles

Thiourea-functionalized magnetic coffee residue for adsorption and magnetic solid-phase extraction of selected toxic metals in water

Herein, a recyclable thiourea-modified magnetic coffee residue was prepared, characterized, and investigated for Cd(II) and Pb(II) adsorption and magnetic solid-phase extraction in aqueous solutions. Optimal conditions of the adsorption parameters were found to be initial Cd(II) and Pb(II) concentrations of 4 and 20 mg/L, respectively, sample solution pH of 7, adsorbent amount of 50 mg, agitation rate of 150 rpm, and adsorption period of 30 min. The adsorption isotherm and kinetics aligned well with the Langmuir and the pseudo-second-order models, respectively. The modified magnetic coffee residue demonstrated a high uptake potential (mg/g), 8.9 for Cd(II) and 40 for Pb(II). The results indicate that chemosorption is the rate-limiting and that temperature influences the process. The elution procedure was performed by 5 mL 0.5 M thiourea in 2 % HCl and the developed magnetic solid-phase extraction technique presented excellent linearity (R2 ≥0.998), sensitivity (LOD (µg/L), 0.18 and 0.93 respectively for Cd(II) and Pb(II)), and precision (%RSD, ≤2.7 %). Compared to the reported techniques, the method is highly effective, environmentally friendly, and easily accessible. It also demonstrated good potential (%R, 92.5–99.0 %) when applied to real-world water samples. In conclusion, the developed techniques are recommended for the adsorption and magnetic solid-phase extraction of toxic metals in water systems.

Adsorption of toxic metals from landfill leachate using orange and banana peel powders as adsorbents

Adsorption of toxic metals from landfill leachate using orange and banana peel powders as adsorbents

Adsorption of toxic metals from greywater using coconut husk biochar and spent green tea

The discharge of wastewater into ground and surface waters can cause human and ecological health problems, hence eco-friendly, sustainable and cost-effective methods for removing toxic metals from wastewater are required. The study employed coconut husk biochar and spent impra ginseng flavoured green tea to adsorb cadmium (Cd), chromium (Cr) and lead (Pb) from greywater. The adsorption capacity of coconut husk biochar ranged from 88.70 % to 98.20 % for cadmium, 78 %–96 % for chromium and 95.71 %–99.29 % for lead whilst the spent impra ginseng flavoured green tea ranged from 94.03 % to 96.87 % for cadmium, 52 %–74 % for chromium and 98.52 %–99.48 % for lead. The maximum adsorption capacity (Qe) of coconut husk biochar ranged from 235.64 to 1132.40 mg/g for Cd, 1.31–8.80 mg/g for Cr and 58.85–415.80 mg/g for Pb. Lead demonstrated the highest affinity for the binding of coconut husk biochar and spent impra ginseng flavoured green tea adsorbent with a trend of Pb > Cd > Cr. Coconut husk biochar and spent impra ginseng flavoured green tea adsorbent were suitable for the toxic metals adsorption in the greywater. Cr showed different removal efficiencies where coconut husk biochar showed more effective removal than spent impra ginseng flavoured green tea. The application of coconut husk biochar and spent impra ginseng flavoured green tea in wastewater treatment is a green technology means and can lead to zero pollution of freshwater.

Refining hydrogel-based sorbent design for efficient toxic metal removal using machine learning-Bayesian optimization

Hydrogel-based sorbents show promise in the removal of toxic metals from water. However, optimizing their performance through conventional trial-and-error methods is both costly and challenging due to the inherent high-dimensional parameter space associated with complex condition combinations. In this study, machine learning (ML) was employed to uncover the relationship between the fabrication condition of hydrogel sorbent and their efficiency in removing toxic metals. The developed XGBoost models demonstrated exceptional accuracy in predicting hydrogel adsorption coefficients (Kd) based on synthesis materials and fabrication conditions. Key factors such as reaction temperature (50–70 °C), time (5–72 h), initiator ((NH4)2S2O8: 2.3–10.3 mol%), and crosslinker (Methylene-Bis-Acrylamide: 1.5–4.3 mol%) significantly influenced Kd. Subsequently, ten hydrogels were fabricated utilizing these optimized feature combinations based on Bayesian optimization, exhibiting superior toxic metal adsorption capabilities that surpassed existing limits (logKd (Cu): increased from 2.70 to 3.06; logKd (Pb): increased from 2.76 to 3.37). Within these determined combinations, the error range (0.025–0.172) between model predictions and experimental validations for logKd (Pb) indicated negligible disparity. Our research outcomes not only offer valuable insights but also provide practical guidance, highlighting the potential for custom-tailored hydrogel designs to combat specific contaminants, courtesy of ML-based Bayesian optimization.

Adsorption and ion exchange of toxic metals by Brazilian clays: clay selection and studies of equilibrium, thermodynamics, and binary ion exchange modeling.

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni2+, Cd2+, Zn2+, and Cu2+). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process. The clays expanded vermiculite (EV) and VNa-sodified vermiculite were evaluated by equilibrium study at 25, 35, and 45 °C. At 25 °C, EV obtained a maximum adsorption capacity of 0.368 mmol/g and sodified vermiculite 0.480 mmol/g, which represents an improvement of 30.4% in modified clay capacity. At 45 °C, the sodified vermiculite reached 0.970 mmol/g adsorption capacity. The Langmuir, Redlich-Peterson Freundlich, and Dubinin-Raduskevich models were adjusted to the results. Langmuir provided the best fit among the models. The thermodynamic quantities (ΔS, ΔH, and ΔG) demonstrated that the process is spontaneous and endothermic and the metal is captured by physisorption and chemisorption in the studied temperature range. For the ion exchange equilibrium, the binary Langmuir and binary Langmuir-Freundlich models were adjusted to the expanded vermiculite and sodified vermiculite isotherms, respectively. Both models were predictive. Thermal analysis indicated good heat resistance even after material modification. The apparent and real densities demonstrated that after each treatment or contamination, the clayey material undergoes contraction in its structure. An improved efficiency of the adsorbent was found after sodification.

Soft computing models for prediction of bentonite plastic concrete strength

Bentonite plastic concrete (BPC) is extensively used in the construction of water-tight structures like cut-off walls in dams, etc., because it offers high plasticity, improved workability, and homogeneity. Also, bentonite is added to concrete mixes for the adsorption of toxic metals. The modified design of BPC, as compared to normal concrete, requires a reliable tool to predict its strength. Thus, this study presents a novel attempt at the application of two innovative evolutionary techniques known as multi-expression programming (MEP) and gene expression programming (GEP) and a boosting-based algorithm known as AdaBoost to predict the 28-day compressive strength ( ) of BPC based on its mixture composition. The MEP and GEP algorithms expressed their outputs in the form of an empirical equation, while AdaBoost failed to do so. The algorithms were trained using a dataset of 246 points gathered from published literature having six important input factors for predicting. The developed models were subject to error evaluation, and the results revealed that all algorithms satisfied the suggested criteria and had a correlation coefficient (R) greater than 0.9 for both the training and testing phases. However, AdaBoost surpassed both MEP and GEP in terms of accuracy and demonstrated a lower testing RMSE of 1.66 compared to 2.02 for MEP and 2.38 for GEP. Similarly, the objective function value for AdaBoost was 0.10 compared to 0.176 for GEP and 0.16 for MEP, which indicated the overall good performance of AdaBoost compared to the two evolutionary techniques. Also, Shapley additive analysis was done on the AdaBoost model to gain further insights into the prediction process, which revealed that cement, coarse aggregate, and fine aggregate are the most important factors in predicting the strength of BPC. Moreover, an interactive graphical user interface (GUI) has been developed to be practically utilized in the civil engineering industry for prediction of BPC strength.

Nanocellulose: A sustainable functional construct for the remediation of heavy metal ions from water

Heavy metals are considered to be a significant pollutant in water bodies, adversely affecting human health by causing various severe diseases after passing down the food chain. The rise in environmental problems due to the usage of non – biodegradable materials leads to the necessity of eco–friendly materials. The abundant and eco-friendly nature of the nanocellulose makes them promising substitutes for non-sustainable materials, nowadays. It is also possible to find the chemical components (cellulose, hemicellulose, and lignin) present in a source and the cellulose yield. In this context, nanocellulose has gained considerable attention among nanomaterials as a promising candidate for the adsorption of toxic heavy metal ions because of its large surface area, light weight, low cost, biocompatible nature, etc. Moreover, the numerous surface hydroxyl groups present in its surface make them suitable for the wide range of surface functionalization with different groups. They can thus be used individually or in combination with other materials for excellent adsorption towards various toxic heavy metal ions. The state of research on modified nanocellulose as an adsorbent for heavy metals is principally discussed in this review. Mainly two types of plant-based nanocelluloses; cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs), are discussed in detail in this review. The extraction of nanocellulose via a green approach was also covered. This review comprises comprehensive details on the modifications and other relevant properties of nanocellulose which would facilitate the adsorption of toxic heavy metals.

Preparation of iron composite filler for PRB technology and its application in the removal of toxic metals(loids) from groundwater

Iron-based materials have garnered significant research interest due to their high surface reactivity, exhibiting potential for remediating metal(loid)s in groundwater. However, agglomeration and blockage limit its long-term and stability performance in application in permeable reactive barrier (PRB) technology. In this study, three innovative and low-cost iron composite fillers were prepared using a mass-producible impregnation method and applied as fillers for PRB. Static sorption and dynamic column experiments were conducted to assess the long-term performance of these composites to remediate multiple toxic metals(loids) contaminated groundwater. The results showed that the iron composite fillers had the excellent adsorption capacities for Co(II), Cu(II), Cr(VI) and As(III) from simulated contaminated groundwater even under the interference of Fe(III) and Mn(II). The pH of the influent favored the adsorption of toxic metals(loids) by the iron composite fillers in the order of 3.00＞5.00＞8.00＞7.00＞9.00＞6.00. The overall adsorption process was more consistent with the quasi-secondary kinetic equation. The corresponding constant values of Cr, Co, Cu, and As on CZ were 0.022, 0.093, 0.756, and 0.342 h−1, respectively. And that of CP-I and CP-II were 0.004, 0.022, 0.001, 0.126, 0.008, 0.041, 0.001, and 0.154 h−1, respectively. The specific surface area of the composite zeolite (Na92Al92Si100O384) and composite pumice was 48.185 m2/g and 0.63 m2/g, respectively. The dynamic column experiment was run steadily for 40 days, during which the average removal rates of toxic metals(loids) were above 95% and approximate 20 times its own volume of contaminated water was purified. FeO(OH) on composite zeolite and Fe3O4 on composite pumice played a dominant role in the removal of toxic metals(loids). The toxic metals(loids) adsorbed in the PRB were mainly in a stable phase of residual fraction and Fe-Mn oxide fraction, making them less likely to cause secondary pollution problems.

Adsorption of Toxic Metals Using Hydrous Ferric Oxide Nanoparticles Embedded in Hybrid Ion-Exchange Resins.

Acid mine drainage (AMD) is a major environmental problem caused by the release of acidic, toxic, and sulfate-rich water from mining sites. This study aimed to develop novel adsorbents for the removal of chromium (Cr(VI)), cadmium (Cd(II)), and lead (Pb(II)) from simulated and actual AMD using hybrid ion-exchange resins embedded with hydrous ferric oxide (HFO). Two types of resins were synthesized: anionic exchange resin (HAIX-HFO) for Cr(VI) removal and cationic exchange resin (HCIX-HFO) for Cd(II) and Pb(II) removal. The resins were characterized using scanning electron microscopy and Raman spectroscopy, which confirmed the presence of HFO particles. Batch adsorption experiments were conducted under acidic and sulfate-enhanced conditions to evaluate the adsorption capacity and kinetics of the resins. It was found that both resins exhibited high adsorption efficiencies and fast adsorption rates for their respective metal ions. To explore the potential adsorption on actual AMD, HCIX-HFO demonstrated significant removal of some metal ions. The saturated HCIX-HFO resin was regenerated using NaCl, and a high amount of the adsorbed Cd(II) and Pb(II) was recovered. This study demonstrates that HFO-embedded hybrid ion-exchange resins are promising adsorbents for treating AMD contaminated with heavy metals.

Low swelling Alginate/Lignin network gels with redox responsiveness for sustained release of agricultural fungicide and Pb2+ complexation

Fungicides are among the most essential agrochemicals for controlling crop diseases. However, the increased consumption of fungicides has resulted in environmental pollution and adversely affected human health. The slow-release technology can improve the efficacy and reduce the required amount of fungicide. Here, we developed a low-swelling redox-responsive alginate/lignin network bearing covalently conjugated fungicide thymol-Cl. Natural reductants in the environment caused the selective cleavage of disulfide bonds and release of thymol-Cl and thiazolidin-2-one (a by-product), which both could inhibit the phytopathogenic fungus (F. oxysporum). At the same time, metal chelating groups in the gel endow strong interactions with heavy metal ions for improving soil remediation and preventing the adsorption of toxic metals by the plant roots. The fungicide-loaded carrier could alleviate the poisonous effect of fungi on maize seeds. Indeed, the secretion of natural reducing agents by fungi and maize led to the cleavage of disulfide bonds and the release of fungicides.

Migration and transformation of phosphorus and toxic metals during sludge incineration with Ca additives

The recycling and utilization of phosphorus resources in sludge is becoming increasingly important. In this study, we compared the conversion of phosphorus and toxic metal passivation effects of different Ca additives under oxygen-rich combustion conditions and elucidated their specific mechanisms of action. The experimental results indicated that four Ca-based additives improved the recovery rate of total phosphorus, and promoted the generation of stable apatite phosphorus (AP). The effect of CaCl2 and CaO was greater than that of Ca(OH)2 and CaSO4. CaCl2 promoted the formation of Ca3(PO4)2 and Ca2P2O7, and CaSO4 improved the conversion of AlPO4 to Ca(H2PO4)2 with increasing temperature. The conversion capacity of CaO on non-apatite inorganic phosphorus to AP was greater than that of Ca(OH)2, and more CaH2P2O7, Ca(PO3)2, and Ca–Al–P minerals were found. Toxic metal percentages decreased after sludge incineration with CaCl2. Compared with CaO and Ca(OH)2, the toxic metal adsorption effect of CaSO4 was more significant. The influence of Ca additives on the conversion of Zn into stable components was as follows: CaCl2 > Ca(OH)2 > CaO > CaSO4. Ca additives reduced the toxic metal contamination level and ecological risk index values, and the order of toxic metal contamination levels was Ni > Zn > Cr > Cu > Mn. The experiment confirmed the conversion of phosphorus and the toxic metal passivation effect of Ca additives during oxy-fuel combustion of sludge, which is beneficial for its resource utilization.

Sulfide-modified magnetic titanium dioxide microparticles for the adsorption and solid-phase extraction of toxic metals in aqueous samples

In this work, sulfide-modified magnetic titanium dioxide microparticles (magnetic TiO2-µPs@S) were synthesized and studied for adsorption-based removal and extraction of Cd(II), Co(II), Cu(II), Mn(II), and Ni(II) ions in aqueous solutions before FAAS analysis. The magnetic TiO2-µPs@S was well characterized by UV-vis, FTIR, XRD, SEM, and EDS techniques, and the material was well functionalized, pure, and had a slightly rod-like morphology. Under optimized conditions, initial concentration of 10 mg/L, sample solution pH of 7, adsorbent dose of 0.5 g/L, agitation speed of 200 rpm, and contact time of 45 min, the magnetic TiO2-µPs@S exhibited an adsorption capacity of 24.0, 34.9, 37.6, 38.5, and 27.9 mg/g for Cd(II), Co(II), Cu(II), Mn(II), and Ni(II), respectively. Then after, the desorption experiment was conducted using 5 mL of 0.2 M HNO3 as an eluting solvent. The method showed excellent linearity (R 2 ≥ 0.998) in 0.05–10 mg/L concentration range. The limits of detection and quantification of the developed method were found to be in the range of 0.14–0.81 and 0.47–2.73 µg/L, consecutively, indicating high sensitivity of the proposed method, and <3% RSD was obtained. Furthermore, its practical applicability was assessed on tap water, lake water, and wastewater samples, and satisfactory percent recovery values, 84.5–114%, were acquired. These results indicate the potential applicability of the developed method. In general, the magnetic TiO2-µPs@S can be used as an effective adsorbent for removing heavy metals, and the adsorbent-based solid-phase extraction can be considered a promising technique for extracting and enriching heavy metals from aqueous solutions.

Mono and simultaneous adsorption of aldrin and toxic metals from aqueous solution using rice husk biochar

Recent research has explored the potential of rice husk biochar as a low-cost adsorbent for the removal of contaminants from aqueous solutions, including aldrin, mercury (Hg2+), lead (Pb2+), and cadmium (Cd2+). Experimentation involved adding varying doses of biochar to wastewater with different contamination levels, agitating the mixture for 60 min, and filtering the solutions for analysis. The experiment revealed impressive removal efficiencies: 100% for aldrin, 99.92% – 99.99% for Hg2+, 95.90% – 99.52% for Pb2+, and 88.60% – 99.46% for Cd2+. In binary and quaternary mixtures, Hg2+ showed higher removal efficiency than Pb2+ and Cd2+, with the exception of aldrin. The adsorption order was identified as aldrin &gt; Hg2+ &gt; Pb2+ &gt; Cd2+. The Freundlich adsorption isotherm best described heavy metals in the mono and quaternary component adsorption, while the Langmuir adsorption isotherm was a better fit for the binary component. Consequently, the study highlights rice husk biochar as an efficient, sustainable, and environmentally friendly option for wastewater treatment.

Sustainable developmental measures for the treatment of pharmaceutical industry effluent using nano zero valent iron technology (nZVI) – A review

Among the diverse nanomaterials, nanoscale zero-valent iron (nZVI) particle is one of the superior materials used for the condition of remediation and environmental restoration. As a result of the nanoscale dimension of nZVI particles and its relatively high surface, it is capable of undergoing various chemical reactions, including reduction, oxidation and adsorption of toxic metals, inorganic substances and organic compounds. In the pharmaceutical industry, mass production of drugs results in the widespread dumping of effluents. As emerging pollutants, antibiotics are non-biodegradable compounds that have potential to adversely affect human genetic and hormonal systems posing a risk to human health and the environment. Global health is endangered by antibiotics present in surface waters and drinking water. Drug contaminants can be removed using a synergistic process involving various advanced methods, including ozonation, fenton process, photocatalytic degradation, reverse osmosis and, adsorption techniques. The enhancement of nZVI composites and earlier studies were reviewed, as well as the evaluation of zero valent iron nanoparticles' effectiveness in eliminating antibiotic effluents from water bodies. This review also revealed the various methods of the determination of toxicity associated with nZVI treated pharmaceutical effluents. The present study would suggest the possible utilization of nZVI technology for the effective removal of hazardous pharmaceutical contaminants through sustainable green measures.

Facet-Dependent Competitive Adsorption Mechanisms of Chromate and Oxalic Acid on γ-FeO(OH) Nanocrystals.

Facet-dependent toxic metal adsorption of iron oxides widely occurred in natural environments. It is known that organic acids can alter the adsorption behaviors of trace elements by cooperative or competitive effects. However, the coadsorption mechanisms of the specific facets are still not fully understood. In the current investigation, Cr(VI) adsorption onto the lepidocrocite (γ-FeO(OH))-exposed facets in the presence of oxalic acid (OA) was studied using macroexperiments, in situ attenuated total reflectance Fourier transform infrared spectroscopy, X-ray adsorption fine structure, and density functional theory calculations. Rod-like lepidocrocite (R-LEP) with a high ratio of {001}/{010} facet showed excellent Cr(VI) adsorption capacity than that of plate-like lepidocrocite (P-LEP, the dominant facet is {010}) in the absence/presence of OA. Interestingly, OA reacted with R-LEP would be easier to diminish Cr(VI) adsorption than with P-LEP. The competitive adsorption occurred on the {001} facet due to the formation of inner-sphere OA configurations (monodentate mononuclear and bidentate mononuclear structures) and a bidentate binuclear Cr(VI) complex. However, OA coordinated with {010} facets via the outer-sphere complexes, while Cr(VI) could form a protonated monodentate binuclear configuration. These observations suggest that the competitive adsorption processes between OA and Cr(VI) exhibit facet dependence. Furthermore, lepidocrocite-exposed facets determine the interfacial interactions and geochemical behaviors of Cr(VI) in polluted environments.

Binary and ternary metals adsorption from greywater using spent green tea as a novel adsorbent

Adsorption is one of the most easy-to-operate, less costly, efficient and, most importantly, environmentally friendly methods of removing toxic metals from aqueous environments. We used spent Impra Green Tea Ginseng Flavoured to recover mercury (Hg2+), lead (Pb2+) and cadmium (Cd2+) in binary and ternary systems from greywater. We undertook this study in binary and ternary systems at adsorbent dosages with a corresponding 100 mL varied initial metal concentrations of the greywater. The adsorption efficiency at varied concentrations and dosages in the binary systems by the spent tea waste ranged from 38.5% to 100% for lead, 11.50% to 100% for cadmium and was 100% for mercury. In the ternary system, the adsorption efficiency of toxic metals ranged from 28.91% to 72.85% for cadmium and was 100% for mercury and lead. The maximum adsorption capacity (Qe) for toxic metals in the binary system ranged from 38.46 to 81.97 mg/g for Pb2+ and 12.64 to 56.82 mg/g for Cd2+. The Langmuir adsorption isotherm model was the best fit for the adsorption of toxic metals by Impra Green Tea Ginseng Flavoured. The pH under which the experiments were conducted showed very high removal efficiency for lead and mercury but lower removal efficiencies for cadmium. Spent Impra Green Tea Ginseng Flavoured can be used as an effective and low-cost adsorbent of toxic metals from greywater or wastewater. Based on our findings, further studies should be conducted to determine the effects of varying the contact time, temperature and elevated metal concentrations in the greywater or other wastewater. Significance: This study provides useful information on how spent Impra Green Tea Ginseng Flavoured can be used as an effective and low-cost adsorbent of toxic metals from greywater or wastewater.

Synthesis and characterization of peanut hull modified chitosan beads.

The incorporation of plant materials is an effective method to improve the stability of chitosan beads, as it further increases the adsorption of toxic dyes and metals from aqueous systems. In the present study, chitosan gels were impregnated with a novel type of powder as the groundnut hull powder in order to form composite beads by using a simple droplet-based microfluidic system. The beads were then characterised through various techniques such as SEM, TGA, FTIR, and XRD. Microscopic imaging revealed a change in the surface morphology of the composite beads, which became rough and wrinkled with more valley-like features and irregular cracks. FTIR data suggest that the impregnation of groundnut hull powder led to an increase in functional groups. The thermal analysis allowed for the assessment of composite bead hydration contents and indicated the presence of groundnut hull entrapped in the loaded beads, which was corroborated by vibrational spectroscopy. XRD analysis allows us to conclude that there is an involvement of groundnut hull in the chitosan gels, and the consequence of that is the formation of amorphous beads, which would make them suitable for the adsorption of toxic dyes and metals from water systems.

Functionalized magnetic graphene oxide composites for selective toxic metal adsorption

In this work, composites of magnetite and graphene oxide were modified with amino groups to improve chromium selectivity in a multielement solution containing Cd(II) and Cu(II) ions. The results achieved from characterization techniques such as Fourier transform infrared, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy, confirmed the effectiveness of the synthesis and evidenced different moieties able to promote metal adsorption. Comparing the unmodified composites with the silanized one, it was observed an enhancement in Cr(VI) uptake of 86% relative to Cd(II) and 23% relative to Cu(II). This effect was attributed to the hard-hard interactions of Cr(VI) with nitrogen and to the presence of NH3+ groups that improve the adsorption of chromium negative species. The metal adsorption by the composites followed the Langmuir isotherm model and a pseudo-second order kinetic, and the surface charge played an important role in the adsorption. Finally, reuse experiments showed an adsorption of approximately 100% of Cr(VI) over 5 cycles, underlining the remarkable stability of the produced amino grafted material.

Enhanced separation capacity of carbonaceous materials (hydrochar, biochar, and activated carbon) toward potential toxic metals through grafting copolymerization

Oxygen-containing groups on the surfaces of materials (i.e., –COOH and –OH) are vital to the adsorption of toxic metals. Acrylic acid is used as a green grafter to enhance the density of these groups in carbonaceous materials, whereas ammonium cerium nitrate is used as an initiator. Hydrochar (prepared via hydrothermal carbonization at 190 °C), biochar (generated via pyrolysis at 800 °C), and activated carbon (AC; generated via chemical activation with K2CO3 at 800 °C) derived from ginger residues are used as feedstock materials for the grafting process. Carbonaceous materials are characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, and zeta potential measurements. Cu2+, Cd2+, and Pb2+ are selected as adsorbates. Equilibrium adsorption experiments for the three metal ions on ungrafted and grafted carbonaceous materials are conducted at 25 °C and pH 5.0. Results indicated that the oxygen content in the grafted material is higher than that in the ungrafted material. Grafting can increase the number of OH and COOH functional groups on the carbonaceous materials, thus resulting in more metal ions being absorbed. The Langmuir maximum adsorption capacity (Qmax) of the carbonaceous materials for the toxic metal ions (mol/kg) is ranked in the order Cu2+ > Cd2+ > Pb2+. The amount of potentially toxic metal ions adsorbed on the ungrafted and grafted (abbreviated as G) materials are in the order hydrochar > AC > biochar. The Qmax values of hydrochar (72.8, 74.7, and 109.3 mg/g), biochar (53.6, 69.1, and 53.9 mg/g), AC (54.4, 73.1, and 101.8 mg/g), G-hydrochar (130.9, 146.0, and 271.4 mg/g), G-biochar (92.6, 143.6, and 153.6 mg/g), and G-AC (96.3, 146.1, and 259.1 mg/g) for the adsorbing metals (Cu2+, Cd2+, and Pb2+) are higher than that of commercial activated carbon (21.83, 22.13, and 25.15 mg/g, respectively). The adsorption capacity of the grafted hydrochar is restored after five adsorption–desorption cycles. The primary adsorption mechanisms are complexation and ion exchange.

Adsorption of toxic metals from landfill leachate onto guinea fowl eggshells in the era of green chemistry

One of the best and most affordable ways to remove harmful metals from water is by adsorption. This study investigated the efficiency of guinea fowl (Numida meleagris) eggshells as a low-cost adsorbent for cadmium (Cd) and nickel (Ni) removal from landfill leachate. In replicas, 100 mL wastewater was added to each of the weighed adsorbent dosages (1 g, 1.5 g, 2 g, 2.5 g, 3.0 g, and 3.5 g) in a flat-bottom flask and agitated for 60 minutes at pH of 7.82 and temperature 24 °C. The adsorption efficacy of cadmium and nickel by guinea fowl eggshells were 90.5% to 96.5% and 96.1% to 99.3%, respectively. The maximum adsorption capacity of cadmium was 4.89 × 10-2 mg/g and an adsorption equilibrium (KL) 22.74 mg/L. The Langmuir isotherm model was better fitted to the results of the experiment than the Freundlich isotherm model.