Heavy Metal Adsorption Capacity Research Articles

Preparation of basic magnesium carbonate nanosheets modified pumice and its adsorption of heavy metals.

Heavy metal pollution in wastewater poses a grave danger to the environment and the human body. Pumice is a mineral with abundant reserves and low prices, and its prospect of heavy metal adsorbent is very broad. In this work, we modified pumice with basic magnesium carbonate nanosheets by a convenient hydrothermal synthesis. The adsorption capacity of heavy metals is greatly improved. The effects of different pH and adsorption dosages are investigated. All the optimum pH values for Cu2+, Pb2+, and Cd2+ are 5. The adsorption of three kinds of ions conforms to the quasi-second-order adsorption kinetics model. The theoretical adsorption capacities of Cu2+, Pb2+, and Cd2+, which are calculated by the Langmuir model, are 235.29mg/L, 595.24mg/L, and 370.34mg/L, respectively. The adsorption of Cu2+ and Cd2+ fit the Langmuir model better. The Freundlich model is fitted well with the adsorption of Pb2+. In the experiment simulating real wastewater, the adsorption capacity of heavy metals is not affected. It also shows good reusability in three regeneration cycles. And Mg5(CO3)4(OH)2·4H2O@pumice adsorption column showed the good removal efficiency of three heavy metals at different concentrations and different spatial velocities in the column experiment. Thus, it is believed that the Mg5(CO3)4(OH)2·4H2O@pumice is a promising adsorbent for the efficient removal of heavy metals.

Synthesis of Na-A zeolite loaded bentonite and its application for removal of Cu(II) from aqueous solutions

Zeolites are highly valued as adsorbent materials for the removal of heavy metals due to their exceptional adsorption properties, ease of synthesis, stability, and high adsorption capacity. Bentonite is an abundant and cheap adsorption material, and its aluminosilicate layers have large spacing to accommodate massive hydrated ions or macromolecular organics. In this study, bentonite is designed as the carrier material and Na-A zeolite is synthesized between its aluminosilicate layers, in order to obtain a low-cost modified bentonite with high heavy metal adsorption capacity. Results demonstrate that Na-A zeolite could be satisfactorily synthesized between bentonite aluminosilicate layers at a low synthesis temperature (80 °C) and short time (10 h). The pseudo-second-order kinetic model is more appropriate for characterizing the Cu(II) adsorption process on Na-A zeolite loaded bentonite, and the Freundlich isotherm is favorable for fitting the experimental data of Cu(II) adsorption. The Cu(II) adsorption mechanism by this composite material involves both ion exchange and chemical bonding, associated with its lamellar and cubic combined microstructure.

Use of biochar as a low-cost adsorbent for removal of heavy metals from water and wastewater: A review

In recent years, the removal of heavy metals from water and wastewater systems remains a challenging issue globally. Adsorption technology is widely used for the removal of heavy metals from aquatic systems due to several advantages including its simple operation, low cost and high efficiency. Biochar, which is an environmental benign and low-cost adsorbent, is increasingly used for remediation of heavy metal pollution in aquatic systems. This review critically analyzes recent developments on the biochar-based adsorptive removal of heavy metals from water and wastewater. Biochar is effective for the removal of several toxic metals (As, Cr and Mn) from groundwater and drinking water. Biochar also shows promising performance for the removal of various heavy metals (Cr, Pb, Cu, Cd and Zn) from wastewater. The heavy metal adsorption capacity of the biochar largely depends on the water/wastewater chemistry (pH, competing ions and initial concentrations of adsorbates), contact time between adsorbates and the adsorbent, adsorbent dose and environmental parameters (temperature). The adsorption isotherms and kinetics can be well explained by the Langmuir and pseudo-second order models, respectively. The key mechanisms which drive the heavy metal adsorption onto biochar include precipitation and ion exchange. Biochar-based adsorptive decontamination of heavy metal pollution is sustainable due to low environmental impacts, low energy consumption and low-costs. The key knowledge gaps and future research directions for improvement of biochar-based sorption capacities are highlighted. This review would help for the development of effective biochar-based adsorption technology for the removal of heavy metals from aquatic environments.

Synthesis and Characterization of Terpolymer Adsorbents Using Photopolymerization: Investigation of Heavy Metal Adsorption Capacity

In this study, poly(allylphenol-co-methylmethacrylate-co-vinyl imidazole) (PAMV) terpolymer adsorbents were synthesized using the photopolymerization method with 1-vinyl imidazole, methyl methacrylate, and 2-allylphenol monomers. Structural and surface analyzes of PAMV polymers obtained using different mole ratios 1H-Nuclear Magnetic Resonance, Fourier-Transform Infrared Spectroscopy, X-Ray Photoelectron Spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-Ray and thermal characterization were performed using Thermogravimetry methods. Inductively Coupled Plasma Mass Spectrometry was used for adsorption studies. Optimization studies were carried out at different pH values. According to the results obtained, the pH range in which adsorbents operate at maximum efficiency is between 6-10. Although many different metals have been studied, the holding capacity of the obtained polymeric adsorbent on cadmium, chromium and mercury metal ions is quite remarkable.

Study on Heavy Metal Adsorption Capacity According to Modification Conditions with Ca-Zeolite

Study on Heavy Metal Adsorption Capacity According to Modification Conditions with Ca-Zeolite

Study on Heavy Metal Adsorption Capacity According to Modification Conditions with K-Zeolite

Study on Heavy Metal Adsorption Capacity According to Modification Conditions with K-Zeolite

Revolutionizing biochar synthesis for enhanced heavy metal adsorption: Harnessing machine learning and Bayesian optimization

Biochar is widely recognized as an effective approach for mitigating heavy metal pollution. However, the utilization of machine learning models to guide biochar preparation and enhance its adsorption performance poses challenges. This study proposed a biochar design strategy guided by the Bayesian optimization algorithm. The strategy involves automated hyperparameter optimization for machine learning model training and exploration of unexplored biochar preparation conditions using the Bayesian algorithm. By leveraging Bayesian algorithms for hyperparameter search, we successfully crafted random forest models, support vector regression models, and back propagation models. In comparison to the previously reported models, these models demonstrated outstanding performance, with the random forest model in particular showcasing superior results (R2 = 0.998; RMSE = 0.027). Using a Bayesian algorithm, it was found that more than 80% of the feature combinations would exceed the upper limit of heavy metal adsorption. Our model revealed that biochar with a mesoporous structure, produced at a pyrolysis temperature of 420 °C, exhibited enhanced heavy metal adsorption capacity. This study presented a novel approach for the rapid development of machine learning models using Bayesian optimization and employed inverse reasoning to guide biochar preparation and enhance adsorption performance.

Aging behavior of microplastics accelerated by mechanical fragmentation: alteration of intrinsic and extrinsic properties.

Microplastics (MPs) inevitably undergo multiple aging processes during their life cycle in the environment. However, the information regarding the mechanical fragmentation behavior of MPs remained unclear, including the changes in the intrinsic properties of aged MPs, the measurement of aging degree, the underlying mechanism, and the interaction with heavy metals. Here, MPs (PS, PP, PET) were aged by crushing (-CR) and ball-milling (-BM) to simulate mild and severe mechanical fragmentation, respectively. Our results indicated that mechanical fragmentation significantly affected the morphology of MPs. The aging degree of MP-BM was deeper compared to MP-CR owing to smaller particle size, larger specific surface area, poorer heat resistance, better hydrophilicity, and richer oxygen-containing functional groups. The carbonyl index (CI) and O/C ratio were used to measure the aging degree of the two mechanical aging treatments. Besides, the mechanism was proposed and the discrepancy between the two treatments was elaborated from three aspects including the excitation energy source, reaction interface, and reaction dynamics. Furthermore, the extrinsic properties of MPs altered with the increase of aging degree; specifically, the adsorption capacities of heavy metals were enhanced. Meanwhile, it was unveiled that the CI value and O/C ratio played a vital role in estimating the adsorption ability of heavy metals. The findings not only reveal the mechanical fragmentation behavior of MPs but also provide new insights into the assessment of the potential risks of the aged MPs via chemical indexes.

Response of Heavy Metals to Microseism in Coal Mining Subsidence Water of Huainan, China

Coal mining causes surface subsidence, and the accumulated water body is constantly affected by the mining microseism in this process. Understanding the relationship between the subsided water quality and microseism plays a special role in assessing the environmental impact of mining activities. Based on sampling and monitoring, analyzing, and evaluating the Pansan subsided water area of Huainan, the influence of microseism activity on heavy metal elements in subsided water was verified. We found that the microseism effects decreased the contents of Zn, Pb, and Cu in the subsided water by 43.76%, 35.88%, and 28.83%, respectively, and Cd was not detected. The mechanism of heavy metal evolution in the water–sediment system under microseism factors was further explored by simulating experiments with similar materials. The results showed that the mining microseism increases the heavy metal adsorption capacity of suspended solids, and the dissolved heavy metals in water were transformed into suspended heavy metals. The heavy metals of subsided water eventually accumulate in the sediment, and the purpose of controlling heavy metal pollution can be achieved through regular cleaning of the bottom sediment.

Protein/Polysaccharide Composite toward Multi-in-One Toxin Removal in Blood with Self-Anticoagulation and Biocompatibility.

Biocompatible adsorbents play an essential role in hemoperfusion. Nevertheless, there are no hemoperfusion adsorbents that can simultaneously remove small and medium toxins, including bilirubin, urea, phosphor, heavy metals, and antibiotics. This bottleneck significantly impedes the miniaturization and portability of hemoperfusion materials and devices. Herein, a biocompatible protein-polysaccharide complex is reported that exhibits "multi-in-one" removal efficacy for liver and kidney metabolism wastes, toxic metal ions, and antibiotics. Through electrostatic interactions and polysaccharide-mediated coacervation, adsorbents can be prepared by simply mixing lysozyme (LZ) and sodium alginate (SA) together in seconds. The LZ/SA absorbent presented high adsorption capacities for bilirubin, urea, and Hg2+ of up to 468, 331, and 497mgg-1 , respectively, and the excellent anti-protein adsorption endowed LZ/SA with a record-high adsorption capacity for bilirubin in the interference of serum albumin to simulate the physiological environment. The LZ/SA adsorbent also has effective adsorption capacity for heavy metals (Pb2+ , Cu2+ , Cr3+ , and Cd2+ ) and multiple antibiotics (terramycin, tetracycline, enrofloxacin, norfloxacin, roxithromycin, erythromycin, sulfapyrimidine, and sulfamethoxazole). Various adsorption functional groups exposed on the adsorbent surface significantly contribute to the excellent adsorption capacity. This fully bio-derived protein/alginate-based hemoperfusion adsorbent has great application prospects in the treatment of blood-related diseases.

Bioinspired and dual-functional nanocellulose aerogels for water disinfection and heavy metal removal

Treating water resources contaminated by pathogenic microorganisms and heavy metals is a great challenge because of the difficulties in developing efficient strategies for water treatment. Traditional adsorbent materials have the drawbacks of high cost, low adsorption efficiency, secondary pollution creation, and a lack of adaptability in removing a wide variety of pollutants. In this study, inspired by the hierarchical fibrous structure and antibacterial property of the natural silkworm cocoon, we developed a guanidine-functionalized sericin/nanocellulose aerogel (GSNA) with a biomimetic skeletal architecture, which holds great promise for achieving hybrid water disinfection and heavy metal removal. The nanocellulose (CNC) fibers integrated into a robust building block with an interconnected structure and mechanical stability. The grafted polyhexamethylene biguanide (PHMB) endows the biomimetic aerogel with exceptional bactericidal activity (7 log reduction against Escherichia coli within 30 min). Benefiting from the abundant surface functional groups on sericin and CNC-PHMB, the obtained aerogel also exhibits superior heavy metal adsorption capacity (571.5 mg/g for Cu). These compelling merits enable the aerogel to disinfect water and remove heavy metal ions simultaneously as a membrane filter. The synthesized GSNA can be a promising candidate for water disinfection and purification because of its facile preparation, cost-effectiveness, and environmentally friendly characteristics.

Equilibrium isotherm and kinetic study of biosorption of cadmium from synthetic water using wastes leaves of Averrhoa carambola

Globally, the discharge of heavy metals into the water bodies is a matter of serious concern. Heavy metals like cadmium are considered as toxic even at very low concentration. Several conventional methods are available to remove heavy metals from the wastewater. They bear high costs, generate high sludge, and consume high energy. Biosorbents provides many beneficial properties due to their good adsorption capacity for heavy metals. The present work focuses on the potential of waste leaves of Averrhoa carambola (WACLP) as an adsorbent for its ability to remove Cd (II) ions from synthetic water by batch experimental process. The adsorbent was characterized by using elemental analysis, Energy Dispersive X-ray or EDAX and Scanning Electron Micrograph (SEM). The batch experiment was carried out considering various parameters such as pH, initial metal ion concentration, contact time and dose of the adsorbent. The fitting of the experimental data was done by Langmuir, Freundlich and Temkin isothermal models. The study on isothermal models revealed that the experimental parameters were best fitted to the Langmuir isothermal model with R2 value of 0. 976.The Kinetic studies showed pseudo second order depicting chemisorption. The results showed that Averrhoa carambola is a good adsorbent for cadmium and hence it can widen the scope and prospects for future studies on heavy metal removal from the aqueous solution.

Insights into interactions of biodegradable and non-biodegradable microplastics with heavy metals.

Biodegradable microplastics (BMPs) are considered to be environmentally friendly compared to non-biodegradable plastics (NMPs). However, BMPs are likely to become toxic during their transport because of the adsorption of pollutants (e.g., heavy metals) onto them. This study investigated the uptake of six heavy metals (Cd2+, Cu2+, Cr3+, Ni2+, Pb2+, and Zn2+) by a common BMPs (polylactic acid (PLA)) and compared their adsorption characteristics to those of three types of NMPs (polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC)) for the first time. The order of heavy metal adsorption capacity among the four MPs was PE > PLA > PVC > PP. The findings suggest that BMPs contained more toxic heavy metals than some NMPs. Among the six heavy metals, Cr3+ showed considerably stronger adsorption than other heavy metals in both BMPS and NMPs. The adsorption of heavy metals on MPs can be well explained using the Langmuir isotherm model, while the adsorption kinetic curves showed the best fit to the pseudo-second-order kinetic equation. Desorption experiments revealed that BMPs released a higher percentage of heavy metals (54.6-62.6%) in the acidic environment in a shorter time (~ 6h) compared to NMPs. Overall, this study provides insights into interactions of BMPs and NMPs with heavy metals and their removal mechanisms in aquatic environment.

Modifying Natural Zeolites to Improve Heavy Metal Adsorption

Problems with increasing heavy metal contents in natural waters are becoming a global issue. At the same time, improved methods for water treatment are becoming increasingly important. In this context, natural zeolites can be used to purify polluted water. In this paper, we investigated how the adsorption capacity of natural zeolites can be improved. Natural zeolites from the Shankanay district, Almaty, Kazakhstan, were used as adsorbent material for experiments on improving the water treatment of heavy metals. We found that the adsorption capacity for heavy metals was increased greatly by thermal activation using furnace treatment. The optimal thermal activation condition was about 550 °C for a duration of 2 h. However, the improved adsorption capacity for different heavy metals varied depending on the heat treatment temperature. Adsorption by the heat-treated zeolites at a temperature of 550 °C was 87% for nickel, 99% for copper and cadmium, and 100% for lead. Adsorption by heat-treated zeolites at a temperature of 500 °C was 78% for nickel, 98% for copper, 83% for cadmium, and 88% for lead. The residual concentration of heavy metals in the filtered water did not exceed the maximum permissible concentrations for drinking purposes. In all experiments, intense adsorption took place during the first 10 min representing 35 to 61% of the metal ions in the water. Adsorption properties were verified using adsorption capacity (BET), IR spectroscopy, and scanning electron microscopy. The study shows that modified Shankanay natural zeolites have great potential as a low-cost adsorbent material for purifying water from heavy metals.

The types of microplastics, heavy metals, and adsorption environments control the microplastic adsorption capacity of heavy metals.

Anthropogenic development has released large amounts of microplastics (MPs), which are carriers of migratory heavy metals, into the environment, and heavy metal adsorption by MPs may have strong combined toxic effects on ecosystems. However, until now, a comprehensive understanding of the factors influencing these adsorption capacities of MPs has been lacking. Thus, we used 4984 experimental data points to systematically assess the factors influencing the adsorption strength of 8 types of MPs on 13 types of heavy metals. We found that (1) the types of MPs, heavy metals, and adsorption environments significantly impacted the heavy metal adsorption capacities of MPs; (2) polyvinyl alcohol (PVA) showed a higher adsorption capacity for lead (Pb) and cadmium (Cd) than did other MPs, by 2810.62mg/kg and 2732.84mg/kg, respectively; (3) the adsorption capacities of MPs for heavy metal were regulated by multiple variables, with heavy metal concentration, MP quality, solution amount, adsorption time, and pH being the most important; and (4) MPs had a higher adsorption capacity in aquatic environments (except for seawater) than which in soil environments. Overall, our study clearly showed that the types of heavy metals, adsorption environments, and MPs influenced the heavy metal adsorption capacities of MPs and may exacerbate their combined environmental toxicity, which would help better characterize the severity of MP pollution.

Multifunctional fully biobased aerogels for water remediation: Applications for dye and heavy metal adsorption and oil/water separation

Water ecosystem contamination from industrial pollutants is an emerging threat to both humans and native species, making it a point of global concern. In this work, fully biobased aerogels (FBAs) were developed by using low-cost cellulose filament (CF), chitosan (CS), citric acid (CA), and a simple and scalable approach, for water remediation applications. The FBAs displayed superior mechanical properties (up to ∼65 kPa m3 kg−1 specific Young’s modulus and ∼111 kJ/m3 energy absorption) due to CA acting as a covalent crosslinker in addition to the natural hydrogen bonding and electrostatic interactions between CF and CS. The addition of CS and CA increased the variety of functional groups (carboxylic acid, hydroxyl and amines) on the materials’ surface, resulting in super-high dye and heavy metal adsorption capacities (619 mg/g and 206 mg/g for methylene blue and copper, respectively). Further modification of FBAs with a simple approach using methyltrimethoxysilane endowed aerogel oleophilic and hydrophobic properties. The developed FBAs showed a fast performance in water and oil/organic solvents separation with more than 96% efficiency. Besides, the FBA sorbents could be regenerated and reused for multiple cycles without any significant impact on their performance. Moreover, thanks to the presence of amine groups by addition of CS, FBAs also displayed antibacterial properties by preventing the growth of Escherichia coli on their surface. This work demonstrates the preparation of FBAs from abundant, sustainable, and inexpensive natural resources for applications in wastewater purification.

Comparison of the adsorption capacity and mechanisms of mixed heavy metals in wastewater by sheep manure biochar and Robinia pseudoacacia biochar.

Under various pyrolysis temperatures, the characteristics and heavy metal adsorption capabilities of biochar obtained from sheep manure (SMB) and Robinia pseudoacacia (RPB) were studied. The results indicated that SMB had higher yields, pH values, and ash contents than RPB. SMB3 and RPB3 have more oxygen-containing functional groups, whereas SMB8 and RPB8 have higher aromaticity and polarity. The maximum adsorption capacities of SMB for Pb2+ (20.2 mg·g-1), Cu2+ (13.9 mg·g-1), Cd2+ (3.2 mg·g-1), and total heavy metals (37.3 mg·g-1) were obtained by SMB3. However, the maximum adsorption capacities of RPB for Pb2+ (7.4 mg·g-1) and Cu2+ (10.5 mg·g-1) were obtained by RPB8. Furthermore, SMB and RPB had relatively higher adsorption capacities for Pb2+ and Cu2+ than for Cd2+. The pseudo-second-order model and the Freundlich Langmuir model provided a good fit to the adsorption kinetics and isotherms, indicating that chemical adsorption was dominant in the heavy metal adsorption by SMB and RPB. According to the contribution of various mechanisms, ion exchange and mineral precipitation were the primary mechanisms responsible for RPB8, while functional group complexation was the dominant mechanism for SMB3. This study provided important information on the comprehensive recycling utilization of SMB and RPB and promoted sustainable development.

Calcium-doped magnetic humic acid nano particles for the efficient removal of heavy metals from wastewater: the role of Ca

ABSTRACT Ca doping is an effective method for improving the adsorption capacity of HA–Fe aggregates and regulating their structures. Understanding the structural characteristics of Ca–HA–Fe aggregates can help explore their microscopic adsorption effect on heavy metals. However, the heterogeneity of HA results in an incomplete understanding of the structural characteristics of the ternary system of Ca–HA–Fe aggregates and adsorption of the quaternary system of Ca–HA–Fe–Pb/Cu/Cd. In this study, interactions between Ca–HA–Fe ternary and Ca–HA–Fe–Pb/Cu/Cd quaternary systems were discussed from a molecular perspective. The structures of the basic structural units of HA were identified. Density functional theory (DFT) was employed to calculate the stable states of basic structural units of HA and Ca2+. The results showed that hydroxyl and carboxyl groups exhibited the highest capacity to bind with Ca2+. The interactions among Ca, HA, and Fe led to the formation of network aggregates. The binding energies of functional groups for heavy metals and the feasibility of ion exchange were calculated by the method of experiment and DFT. According to the contribution of functional group complexation and ion exchange, the ion exchange values for Pb2+, Cu2+, and Cd2+ were 66.71%, 62.87%, and 60.79%, respectively, which indicated that Ca2+ ion exchange showed considerable potential in enhancing the adsorption capacity of heavy metals.

Adsorption and desorption characteristics of heavy metals onto conventional and biodegradable plastics

Biodegradable plastics have been widely used to replace conventional plastics to minimize environmental impacts of plastic packaging. However, before biodegradable plastics decompose in the environment, they could pose a threat to terrestrial and aquatic creatures by acting as vectors of contaminants in the food chain. In this study, conventional plastic bags (CPBs) made of polyethylene and biodegradable plastic bags (BPBs) made of polylactic acid were examined for their heavy metal adsorption. Effects of solution pHs and temperatures on adsorption reactions were investigated. Because of a larger BET surface area, presence of oxygen-containing function groups, and smaller crystallinity, the heavy metal adsorption capacities of BPBs are significantly larger than those of CPBs. Among Cu (up to 791.48 mg⋅kg−1), Ni (up to 60.88 mg⋅kg−1), Pb (up to 1414.58 mg⋅kg−1), and Zn (up to 295.17 mg⋅kg−1), Pb and Ni show the largest and the lowest extents of adsorption onto the plastic bags, respectively. In the different waterbodies in nature, Pb adsorption on the CPBs and the BPBs were 318.09–379.91 and 528.41–764.22 mg⋅kg−1, respectively. Consequently, Pb was selected as the target contaminant in the desorption experiments. After Pb was adsorbed onto the CPBs and the BPBs, Pb could be completely desorbed and released into simulated digestive systems in 10 h. In conclusion, BPBs could be potential vectors of heavy metals, and their suitability as a substitute for CPBs must be thoroughly investigated and confirmed.

Delamination of multilayer Ti3C2Tx MXene alters its adsorpiton and reduction of heavy metals in water

MXenes are considered as an emerging class of two-dimensional (2D) adsorbent for various environmental applications. In this work, two different morphologies of Ti3C2Tx MXene (multilayer (ML-Ti3C2Tx) and delaminated titanium carbide (DL-Ti3C2Tx)) were prepared through mild in situ HF etching and further delamination. The structural differences between the two were explored with a focus on their effects on the performance and mechanism of removing heavy metals from water. In comparison to ML-Ti3C2Tx, DL-Ti3C2Tx had more oxygen-containing functional groups, higher specific surface area (19.713 vs. 8.243 m2/g), larger pore volume (0.135 vs. 0.040 cm3/g), higher maximum Pb(II) adsorption capacity (77.0 vs. 56.68 mg/g), but lower maximum Cu(II) adsorption capacity (23.08 vs. 55.46 mg/g). Further investigation revealed that the removal of Pb(II) by the MXenes was mainly controlled through electrostatic attraction and surface complexation mechanisms, while Cu(II) was removed mainly through surface reduction by Ti-related groups. Because delamination of ML-Ti3C2Tx increased the surface area and surface functional groups, DL-Ti3C2Tx became a better sorbent for Pb(II) in water. During sonication, however, delamination inevitably led to partial oxidation of Ti3C2Tx nanosheets and thus weakened the reducing ability of DL-Ti3C2Tx for Cu(II) in water. Nevertheless, both ML- and DL-Ti3C2Tx not only exhibited excellent heavy metal adsorption capacity under different solution conditions, but also showed good reusability. Findings of this study indicate that Ti3C2Tx MXenes are promising adsorbents for treating heavy metal pollutants in water.