Heavy Metal Remediation Research Articles

Phytoremediation Effect and Soil Microbial Community Characteristics of Jiulong Iron Tailings Area, Jiangxi

The aim of this paper was to explore the remediation effect and mechanism of Wetland pine (Pinus elliottii), Chinese fir (Cunninghamia lanceolata (Lamb.) Hook), and Alder (Alnus cremastogyne Burkill) on heavy metal contaminated soil in the iron tailings of Jiulong Iron Tailings Area. At the same time, the specificity of plant rhizosphere and non-rhizosphere soil microbial community structure and ecological function were analyzed based on macrogenomic sequencing. The results showed that the dominant microbial genera in J1 (control) was Acidobacteria, followed by Proteobacteria and Actinobacteria. The microbial genera with the highest percentage of relative abundance in J2, J3, J4, J5, and J6 (J2, Wetland Pine rhizosphere; J3, Wetland Pine non-rhizosphere; J4, Chinese fir rhizosphere; J5, Alder rhizosphere; J6, Alder non-rhizosphere) were Proteobacteria, followed by Acidobacteria, and Actinobacteria. It was found that Proteobacteria promoted heavy metal solubilization, activated heavy metals, and converted their forms to improve plant uptake of heavy metals. This proves that the microorganisms of Proteobacteria are the key microbial genera in the study of regional heavy metal remediation. The antibiotic resistance genes (ARGs) in microorganisms can respond to the inducement of heavy metals. Here, we investigated the relationship between the abundance of soil microorganisms ARGs and heavy metal pollution in Jiulong Iron Tailings Area. There are significant differences in the quantity and category of ARGs in the rhizosphere and non-rhizosphere soil samples of the three tree species. The results of this study provide the foundation for the theory and practice of remediation of heavy metal contamination in soils of iron tailing areas in Jiulong Iron Tailings Area in similar stand conditions.

Adsorption of Heavy Metals: Mechanisms, Kinetics, and Applications of Various Adsorbents in Wastewater Remediation—A Review

Heavy metal contamination in wastewater is a significant concern for human health and the environment, prompting increased efforts to develop efficient and sustainable removal methods. Despite significant efforts in the last few decades, further research initiatives remain vital to comprehensively address the long-term performance and practical scalability of various adsorption methods and adsorbents for heavy metal remediation. This article aims to provide an overview of the mechanisms, kinetics, and applications of diverse adsorbents in remediating heavy metal-contaminated effluents. Physical and chemical processes, including ion exchange, complexation, electrostatic attraction, and surface precipitation, play essential roles in heavy metal adsorption. The kinetics of adsorption, influenced by factors such as contact time, temperature, and concentration, directly impact the rate and effectiveness of metal removal. This review presents an exhaustive analysis of the various adsorbents, categorized as activated carbon, biological adsorbents, agricultural waste-based materials, and nanomaterials, which possess distinct advantages and disadvantages that are linked to their surface area, porosity, surface chemistry, and metal ion concentration. To overcome challenges posed by heavy metal contamination, additional research is necessary to optimize adsorbent performance, explore novel materials, and devise cost-effective and sustainable solutions. This comprehensive overview of adsorption mechanisms, kinetics, and diverse adsorbents lays the foundation for further research and innovation in designing optimized adsorption systems and discovering new materials for sustainable heavy metal remediation in wastewater.

Bioremediation of PBDEs and heavy metals co-contaminated soil in e-waste dismantling sites by Pseudomonas plecoglossicida assisted with biochar

Biochar-assisted microbial remediation has been proposed as a promising strategy to eliminate environmental pollutants. However, studies on this strategy used in the remediation of persistent organic pollutants and heavy metals co-contaminated soil are lacking, and the effect of the combined incorporation of biochar and inoculant on the assembly, functions, and microbial interactions of soil microbiomes are unclear. Here, we studied 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) degradation and heavy metal immobilization by and biochar-based bacterial inoculant (BC/PP) in an e-waste contaminated soil, and corresponding microbial regulation mechanisms. Results showed that BC/PP addition was more effective in reducing Cu and Pb availability and degrading BDE-47 than inoculant alone. Notably, BC/PP facilitated bound-residue formation of BDE-47, reducing the ecological risk of residual BDE-47. Meanwhile, microbial carbon metabolism and enzyme activities (related to C-, N-, and P- cycles) were enhanced in soil amended with BC/PP. Importantly, biochar played a crucial role in inoculant colonization, community assembly processes, and microbiome multifunction. In the presence of biochar, positive interactions in co-occurrence networks of the bacterial community were more frequent, and higher network stability and more keystone taxa were observed (including potential degraders). These findings provide a promising strategy for decontaminating complex-polluted environments and recovering soil ecological functions.

Magnetic sepiolite/iron(III) oxide composite for the adsorption of lead(II) ions from aqueous solutions

AbstractClay minerals are effective adsorbents used for the remediation of toxic heavy metals from wastewater due to their large surface areas and great cation-exchange capacities. In this study, the removal of lead ions from aqueous solutions via adsorption was investigated using raw and iron-modified Turkish sepiolite. The aim of this study was to examine the effects of modification and environmental conditions on the sorptive properties of sepiolite samples. Initially, the raw sepiolite (Sep) and magnetic sepiolite/Fe2O3 composite (MagSep) prepared using the co-precipitation method were characterized via mineralogical and petrographical means and the physicochemical properties were determined. Then, the batch adsorption of lead (Pb2+) ions on the sepiolite samples was examined under various conditions (solution pH, adsorbent dosage, contact time, initial Pb2+ ion concentration, temperature, shaking rate). The adsorption capacity of MagSep was found to be greater than that of Sep under all experimental conditions. The results showed that the adsorption process followed a pseudo-second-order kinetic model, and the Langmuir isotherm best correlated with the experimental data. The maximum adsorption capacities were found to be 60.6 and 90.1 mg g–1 for Sep and MagSep, respectively. The characterization of the Pb-adsorbed sepiolite samples showed that lead formed covalent bonds with the sepiolite samples and attached to the sepiolite surface mainly through ion exchange. MagSep can be used efficiently in the field of wastewater treatment for the removal of Pb2+ ions as it does not release any toxic pollutants and can be separated easily with the use of a magnetic field.

Bioavailability, Sources, and Transfer Behavior of Heavy Metals in Soil–Crop Systems from a High Geological Background Area Impacted by Artisanal Zn Smelting in Guizhou Province, Southwest China

The environmental risk posed by heavy metals in agricultural soil is primarily influenced by their sources, bioavailability, and geochemical transfer behavior. This study focused on Weining County, a region in Guizhou province, Southwest China, with a high geological background and long-term impact from artisanal Zn smelting. Vertical soil profiles, crop, and rhizospheric soil samples were collected and analyzed for heavy metal concentration (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, V, and Zn) including the total concentration and chemical fraction. The results revealed elevated concentrations of Cd (range: 0.7–6.9 mg·kg−1), Co (range: 19.3–120.0 mg·kg−1), Cu (range: 71.6–386.0 mg·kg−1), Ni (range: 51.0–121.0 mg·kg−1), and V (range: 310.0–721.0 mg·kg−1) in all soil samples compared to the background values of Guizhou Province. Chemical fractionation analysis indicated that Cr, Ni, As, Cu, and Zn were predominantly present in the residual fraction, while Hg and Pb were predominantly found in the potentially bioavailable fraction. Cd exhibited the highest bioavailability, accounting for 58.5% of its total concentration. Enrichment factor analysis suggested that artisanal Zn smelting activities were the main sources of Cd, Pb, and Zn contamination. Furthermore, Cd, Pb, and Zn were found to be highly accumulated in the surface soil layer (0–20 cm). Notably, 90.0% of potato and 9.4% of maize grain samples exceeded the food hygiene standards for Cd concentration, posing potential health risks to consumers. The bioconcentration factor (soil-to-root) and translocation factor (root-to-grain) analyses indicated that maize roots had a higher tendency to accumulate Cd from the soil, while Zn and Cu showed a significant transferability from roots to maize grains. These findings offer valuable insights for devising heavy metal remediation strategies in similar areas.

Morphologically different hydroxyapatite nanoparticles exert differential genotoxic effects in Drosophila

Hydroxyapatite (HAP) occurs naturally in sedimentary and metamorphic rocks and constitutes the hard structures in many organisms. Since synthetic nano-sized HAP (HAP-NPs) are used in orthopedic applications and for heavy metal remediation in aquatic and terrestrial media, both environment and humans are exposed to them. Due to the concerns about their potential hazards, the genotoxic effects that round/rod forms of HAP-NPs were investigated in Drosophila using the wing-spot and the comet assays. Furthermore, caspase activities were evaluated to examine the activation of cell death pathways. As a novelty, the expression of 36 genes involved in DNA repair was investigated, as a tool to indirectly determine DNA damage induction. Obtained sizes were 35–60 nm (roundHAP-NPs) and 45–90 nm (rodHAP-NPs) with a low Zeta-potential (−1.65 and 0.37 mV, respectively). Genotoxicity was detected in the wing-spot (round form), and in the comet assay (round and rod-like HA-NPs). In addition, increased expression of Caspases 3/7, 8, and 9 activities were observed. For both HAP forms, increased changes in the expression were observed for mismatch repair genes, while decreased expression was observed for genes involved in ATM, ATR, and cell cycle pathways. The observed changes in the repair pathways would reinforce the view that HAP-NPs have genotoxic potential, although more markedly in the round form. Thus, the environmental presence of engineered nanoparticles, including HAPs, raises concerns about potential effects on human health. It is essential that the effects of their use are carefully assessed and monitored to ensure safety and to mitigate any potential adverse effects.

Unraveling Microbes as Potential Proxies for Remediation of Heavy Metal and Pesticide Contamination: A State-of-the Art Review

Unraveling Microbes as Potential Proxies for Remediation of Heavy Metal and Pesticide Contamination: A State-of-the Art Review

Integrating land use functions and heavy metal contamination to classify village types

Identifying the dynamic processes of socio-economic development and environmental sustainability is an important measure to prevent environmental degradation and improve human well-being in village areas. However, there is currently a lack of analytical frameworks that integrate socio-economic and environmental security indicators in village areas, making it difficult to accurately identify the ecological environmental status of village areas at different stages of development. This study quantified the multifunctional land use and heavy metal pollution risks of different village areas using land use data and soil samples collected in the field. It then integrated land use functions and heavy metal pollution risks into the analytical framework using hierarchical clustering, which identified different types of village areas. The results show that: (1) The applicability and accuracy of this analytical framework are validated by a sample verification, which classifies village areas into traditional village, productive village, comprehensive village and ecotype village. (2) Most village areas belong to the traditional village with single production and life functions. With the development of village industries, some traditional villages become productive villages. Those closer to cities or with policy support continue to develop into comprehensive villages. In this process, the village socio-economy develops, land use functional services become more diverse, but heavy metal risks gradually increase. (3) Traditional villages should prevent pollution risks from Cd, Zn and other heavy metals. Productive villages should prevent Cu, Ni, Zn, Cr and other heavy metals from industrial and domestic wastewater. Comprehensive villages should strengthen soil remediation and remediation of heavy metal contaminated sites, adjust industrial layout. Ecotype villages should avoid the impact of exogenous pollutants on the region and develop ecotourism industries. Through the classification results and discussion of village area types, this study effectively reveals the differences in environmental risks faced by socio-economic development in typical village areas in China, and provides a basis for governments to formulate functional planning and environmental protection policies suitable for different types of villages.

Bibliometric analysis and systematic review of electrochemical methods for environmental remediation

Electrochemical methods are increasingly favored for remediating polluted environments due to their environmental compatibility and reagent-saving features. However, a comprehensive understanding of recent progress, mechanisms, and trends in these methods is currently lacking. Web of Science (WoS) databases were utilized for searching the primary data to understand the knowledge structure and research trends of publications on electrochemical methods and to unveil certain hotspots and future trends of electrochemical methods research. The original data were sampled from 9080 publications in those databases with the search deadline of June 1st, 2022. CiteSpace and VOSviewer software facilitated data visualization and analysis of document quantities, source journals, institutions, authors, and keywords. We discussed principles, influencing factors, and progress related to seven major electrochemical methods. Notably, publications on this subject have experienced significant growth since 2007. The most frequently-investigated areas in electrochemical methods included novel materials development, heavy metal remediation, organic pollutant degradation, and removal mechanism identification. “Advanced oxidation process” and “Nanocomposite” are currently trending topics. The major remediation mechanisms are adsorption, oxidation, and reduction. The efficiency of electrochemical systems is influenced by material properties, system configuration, electron transfer efficiency, and power density. Electro-Fenton exhibits significant advantages in achieving synergistic effects of anodic oxidation and electro-adsorption among the seven techniques. Future research should prioritize the improvement of electron transfer efficiency, the optimization of electrode materials, the exploration of emerging technology coupling, and the reduction in system operation and maintenance costs.

New insights into the sustainable use of soluble straw humic substances for the remediation of multiple heavy metals in contaminated soil

This study addresses the research gap in understanding the differences in straw decomposition and variations in humic substances (HS) extracted from various treatment conditions. The aim is to explore the potential of soluble straw HS in remediating heavy metal pollution in soils. The study characterizes straw decomposition structures using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while employing gel permeation chromatography (GPC) and fluorescence spectroscopy (EEM) to analyze the molecular weight and degree of humification of extracted straw HS. The removal efficiency of HS for heavy metals is assessed, with a focus on aerobic humic substances (AE-HS) showing the highest potential for heavy metal removal. Spectral analysis and mass spectrometry analysis reveal the role of phenolic compounds, carboxylic acids, and aromatic compounds in AE-HS, forming humates or complexes to remove heavy metals from contaminated soil. Notably, the optimized AE-HS achieved the highest removal efficiency of 96.18 %, 82.75 %, 60.43 %, and 41.66 % for cadmium, copper, zinc, and lead, respectively. This study provides new insights into the preparation of straw for use as a heavy metal remover and has implications for the use of straw humic substances in soil remediation.

Characterization and application of Fe-modified biochar alleviating Cr(VI) stress in pak choi seedling cultivated in Cr-polluted hydroponics

Chromium (Cr) is one of the common environmental pollutants, which causes severe health hazards on human health and environmental security. In this study, we characterized two biochars, a raw biochar (RBC) and a Fe-modified biochar (MBC) made from poplar wood chips and determined the effect of the two biochars on remediation of hexavalent chromium (Cr(VI)) in hydroponic system by monitoring Pak choi growth. Results showed the surface area, pore number and pore volume were significantly higher in MBC than in PBC, but the pore size was larger in PBC than in MBC. When compared to the control, low concentrations of Cr(VI) (≤2 mg L−1) promoted the growth and biomass production of Pak choi by 10–78%. In contrast, the high concentrations of Cr(VI) (≥4 mg L−1) showed a significantly reduction of the growth and biomass production of Pak choi by 10–28%. Fe-modified biochar (MBC) had a more significant impact than RBC on the remediation of Cr in the Cr(VI) pollution and improved growth and biomass production of Pak choi to a greater extent. Our study indicated that MBC has a better effect on degrading Cr(VI) pollution. The findings provide scientific basis and reference for the remediation of heavy metals in aquatic ecosystems by using biochar.

Recyclable and reusable layered double hydroxide beads for soil remediation: Conveying belt recovery model, mechanism, bioavailability and microbial communities

Soil heavy metal remediation has always been the focus of research. This work synthesized a recoverable, reusable, and efficient material for Cr(VI)-contaminated soil through a new strategy. The main structure is a bead that encapsulates the layered double hydroxides(LDHs) and magnetic particles into an alginate bead (LDHs-M). Varying applications in soil suggested LDHs-M showed high immobilization performance. Including LDHs interlayer ions, proportion of components, pH, dosage, and initial Cr(VI) concentration, many influence factors were systemically explored, suggesting that LDHs contained in the bead played a prominent role during the immobilization and LDHs-M with the interlayer anions of NO3- showed excellent immobilization efficiency. Different characterizations were used to investigate the immobilization mechanism, indicating that interlayer anion exchange and electrostatic adsorption were the main ways for soil Cr(VI) immobilization. The toxicity also decreased with the reduction of Cr(VI). Meanwhile, the simulation of natural aging processes, plant growth, and changes in the microbial community in the soil after remediation were also investigated, which verified the immobilizing stability and bioavailability of LDHs-M. Furthermore, the magnetic belt recovery system showed superior recovery performance in solid phase separation. Then, the separated beads were regenerated in an electrolyte solution and reused in soil remediation. The perfect immobility, instantaneous separation, and regenerability made it a promising material in heavy metal contaminated soil.

Performance and Mechanism of Zn-Contaminated Soil through Microbe-Induced Calcium Carbonate Precipitation

Zn is a toxic heavy metal that seriously endangers human health and ecological stability. For a long time, traditional remediation techniques have been used to remediate Zn-contaminated soil prone to other problems such as secondary contamination. In recent years, due to the great danger posed by Zn pollution, there has been an increasing interest in applying eco-friendly and sustainable methods to remediate Zn-contaminated soil. Therefore, in this study, microbially induced calcium carbonate precipitation (MICP) technology was used to bioremediate zinc ions by transforming ionic heavy metals into insoluble solid-phase minerals. Through the unconfined compressive strength (UCS) test, direct shear (DS) test, and penetration test (PT), the results showed that the unconfined compressive strength of the treated specimens increased by 187.2~550.5%, the cohesion increased significantly compared with the internal friction angle of specimens, and the permeability coefficient can be reduced by at least one order of magnitude. During the treatment of Zn pollutants, the mobility of heavy metal zinc ions was significantly reduced, the percentage of exchangeable state Zn content was significantly reduced, and the leaching concentration of zinc ions in Zn-contaminated soil was reduced to about 20 mg/L, which was significantly lower than the limit in the standard (100 mg/L). These results were further confirmed by scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, which indicated coprecipitation of calcium carbonate (CaCO3) and ZnCO3. The microbial solidification/stabilization of Zn-contaminated soil was most effective when the curing age of 28 d, the cementation solution concentration of 1 mol/L, and the cementation solution ratio of 1:2. Therefore, the bio-immobilization of zinc ions by MICP has the potential for application as a low-cost and eco-friendly method for heavy metal remediation.

Deep insight on mechanism and contribution of arsenic removal and heavy metals remediation by mechanical activation phosphogypsum

Arsenic-containing wastewater and arsenic-contaminated soil can cause serious environmental pollution. In this study, phosphogypsum with partial mechanical activation of calcium oxide was used to prepare a new phosphogypsum-based passivate (Ca-mPG), and its remediation performance on arsenic-contaminated soil was evaluated in terms of both effectiveness and microbial response. The results showed that the optimum conditions for the preparation of the passivate were optimized in terms of single factor and response surface with a ball milling speed of 200 r/min, a material ratio of 6:4 and a ball milling time of 4 h. Under these conditions, the adsorption capacity was 37.75 mg/g. The leaching concentration of arsenic (As) in the contaminated soil after Ca-mPG modification decreased from 25.75 μg/L to 5.88 μg/L, which was lower than the Chinese national standard (GB/T 5085.3–2007); Ca-mPG also showed excellent passivation effect on other heavy Metals (copper, nickel, cadmium, zinc). In addition, As-resistant bacteria and passivators work together to promote the stabilization effect of contaminants during the remediation of As-contaminated soil. The mechanisms of Cu, As(III)/As(V), Zn, Cd, and Ni removal were related to ion exchange, electrostatic adsorption of substances on heavy metals, calcium binding to other substances to produce precipitation; and microbially induced stabilization of HMs, oxidized. Overall, this study demonstrates an eco-friendly "waste-soil remediation" strategy to solve problems associated with solid waste reuse and remediation of HM-contaminated soils.

Hydrophilic silver nanoparticles for the treatment of water polluted by heavy metals

Hydrophilic silver nanoparticles (AgNPs) are widely used in advanced biotechnologies, due to their versatile, easy, cheap preparations and due to their peculiar physico-chemical properties. It is well known that their surface functionalization plays a key role in defining the chemical-physical behaviour of AgNPs. If used for monitoring and remediation of heavy metals polluted water, the surface functionalization can direct the selectivity and sensitivity of the nanomaterial. Moreover, different capping agents can also induce different ecotoxicity. In this framework AgNPs are synthetises and properly functionalized using different capping agent, such as citrate (Cit), sodium 3 mercapto-1-propansulphonate (3MPS), L-cysteine (Lcys) and glutathione (GSH). The opportune choice of these capping agents induces size control (in the range of Ø = 2-30 nm) and make available selectively detection of heavy metal ions, such as Co(II), Hg (II) or Fe (III). These investigations confirmed that the multiple functionalized AgNPs are amazing and promising systems for monitoring and treatment of heavy metals polluted water.

Nano-Phytoremediation of Heavy Metals from Soil: A Critical Review

Heavy metal pollution is one of the major global issues arising from various anthropogenic activities. The natural habitat and human health may be at peril from heavy metal exposure since they are tenacious, bio-accumulative, and non-biodegradable. Therefore, eradicating heavy metals from the soil ecosystem is a crucial responsibility to create a secure, viable, and zero-waste ecosystem. There are numerous techniques for eliminating heavy metals from the environment, but each has its own benefits and drawbacks. When a biological agent is used to degrade pollutants, this process is called bioremediation. Nano-phytoremediation, an emerging bioremediation approach in the field of nanotechnology, uses biosynthesized nanoparticles and plant species for the removal of toxic heavy metals from the environment. It is an efficient, economical, and environmentally friendly technique. The adverse consequences of metal exposure on different plant species have been discovered to be greatly reduced by engineered nanomaterials. Because of their tiny dimensions and huge surface area, nanomaterials have an attraction towards metals and can thus quickly enter the contaminated zone of ecosystems that are metal-challenged. The current review provides an overview of various aspects of nano-phytoremediation for heavy metal remediation.

A comparative study of different methods for the determination of cadmium in various tissues of ramie (Boehmeria nivea L.)

Remediation of cadmium (Cd) pollution is one of the priorities of global environmental governance and accurate detection of Cd content is a key link in remediation of Cd pollution. This study aimed to compare three methods (inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and graphite furnace-atomic absorption spectrometry (GF-AAS)) for the determination of Cd with different tissues of various ramie varieties, and distinguish the advantage and disadvantage of each method. In total, 162 samples of ramie (Boehmeria nivea L.), which is an ideal plant for heavy metal remediation, were detected and the results showed that the three methods were all suitable for the de-termination of Cd content in ramie. ICP-OES and ICP-MS were simpler, faster, and more sensitive than GF-AAS. ICP-MS could be recommended for the determination of samples with various concentrations of Cd. ICP-OES could be used for measurement of samples with > 100 mg/kg Cd content, while GF-AAS was suitable for the detection of samples with very high (> 550 mg/kg) or very low (< 10 mg/kg) Cd content. Overall, considering the accuracy, stability, and the cost of measurement, ICP-MS was the most suitable method for determination of Cd content. This study provides significant reference information for the research in the field of Cd pollution remediation.

Removal of Lead (Pb) From Aqueous Solutions Using Exoskeleton of Black Solider Fly (BSF)

Lead (Pb) pollution in water sources poses environmental and public health risk. It is important to mitigate the effects by developed an effective remediation method. The potential use of deceased black soldier fly (Hermetia illucens) to remove Pb from aqueous solutions was studied. The flies were ground into a fine powder, analyzed, and then subjected to adsorption studies using Pb synthetic aqueous solutions. Results showed that the deceased black soldier flies are effective in removing Pb from aqueous solutions. The findings lead to the development of resource-efficient heavy metal remediation methods that use the large biomass of black soldier flies.

Remediation of Heavy Metals Using Biomass-Based Adsorbents: Adsorption Kinetics and Isotherm Models

This study aims to comprehensively investigate the current advances in water treatment technologies for the elimination of heavy metals using biomass-based adsorbents. The enhancement of adsorption capacity in biomass materials is achieved through surface modification, which increases their porosity and surface area. The study therefore focuses on the impact of different surface modification techniques on the adsorption capacity, as well as the evaluation of adsorptive removal techniques and the analysis of various isotherm and kinetics models applied to heavy metal contaminants. The utilization of kinetic and isotherm models in heavy metal sorption is crucial as it provides a theoretical background to understand and predict the removal efficiency of different adsorbent materials. In contrast to previous studies, this research examines a wide range of adsorbent materials, providing a comprehensive understanding of their efficacy in removing heavy metals from wastewater. The study also delves into the theoretical foundations of the isotherm and kinetics models, highlighting their strengths, limitations, and effectiveness in describing the performance of the adsorbents. Moreover, the study sheds light on the regenerability of adsorbents and the potential for their engineering applications. Valuable insights into the state-of-the-art methods for heavy metal wastewater cleanup and the resources required for future developments were discussed.

Biosorption Potential of Desmodesmus sp. for the Sequestration of Cadmium and Lead from Contaminated Water

Industrialization, urbanization, and natural processes have potentially accelerated the pace and level of heavy metals in the aquatic environment. Recently, modern strategies for heavy metal treatment in wastewater have received the specific attention of the scientific community. The present study aimed to assess the amorphous biomass of Desmodesmus sp. as a low-cost adsorbent to remove the cadmium (Cd) and lead (Pb) from aqueous solutions. It involved the optimization of pH, contact time, initial concentration of metal ions, and the dosage of biosorbent. Data collation revealed that an optimum contact time for both metals was 60 min, with an adsorption capacity of 63% for Cd and 66% for Pb. Different models were applied to the equilibrium data. The pseudo 2nd order described the best adsorption of Cd and Pb. The equilibrium data were computed with various isotherms. Langmuir isotherms better suit the adsorption of the above-mentioned metals. Hence, the maximum adsorption capacity of Desmodesmus sp. for Cd and Pb was 64.1 and 62.5 mg/g, respectively. The mechanism of biosorption was validated through a comparative FT-IR and Scanning Electron Microscopy of raw and metal-loaded algal biomass based on cell morphological changes. In order to study the reusability of adsorbent, adsorption-desorption of Cd and Pb ions was repeated three times using HCl. These results did not noticeably change in adsorption capacity during the three cycles. Using HCl (0.1 M), desorption of both metals was achieved up to 90% in three cycles. This work presented a long-term bioremediation approach for heavy metal pollutants in wastewater. This research could be seen as an interdisciplinary approach to large-scale heavy metal remediation. In addition, growing microalgae in wastewater produces animal feed and biodiesel. When compared to other conventional methods for environmental remediation and the manufacture of valuable products, the use of microalgae is a more efficient and cost-effective method.