Method For Removal Of Heavy Metals Research Articles

Toxic heavy metal ions contamination in water and their sustainable reduction by eco-friendly methods: isotherms, thermodynamics and kinetics study

Heavy metal ions can be introduced into the water through several point and non-point sources including leather industry, coal mining, agriculture activity and domestic waste. Regrettably, these toxic heavy metals may pose a threat to both humans and animals, particularly when they infiltrate water and soil. Heavy metal poisoning can lead to many health complications, such as liver and renal dysfunction, dermatological difficulties, and potentially even malignancies. To mitigate the risk of heavy metal ion exposure to humans and animals, it is imperative to extract them from places that have been polluted. Several conventional methods such as ion exchange, reverse osmosis, ultrafiltration, membrane filtration and chemical precipitation have been used for the removal of heavy metal ions. However, these methods have high operation costs and generate secondary pollutants during water treatment. Biosorption is an alternative approach to eliminating heavy metals from water that involves employing eco-friendly and cost-effective biomass. This review is focused on the heavy metal ions contamination in the water, biosorption methods for heavy metal removal and mathematical modeling to explain the behaviour of heavy metal adsorption. This review can be helpful to the researchers to design wastewater treatment plants for sustainable wastewater treatment.

Microalgae-Mediated Biosorption for Effective Heavy Metals Removal from Wastewater: A Review

Environmental contamination by heavy metals poses significant threats to terrestrial and aquatic ecosystems, necessitating the development of effective remediation strategies. Conventional methods for heavy metal removal exhibit limitations, including inadequate efficiency and elevated costs. In this context, microalgae have emerged as a promising bioremediation approach due to their robust metal-binding capabilities, specifically through biosorption. This review comprehensively examines the role of microalgae in addressing heavy metal pollution, with a primary focus on their effective removal from wastewater. Microalgae offer wastewater purification potential across diverse sources and capitalize on wastewater as a growth matrix, yielding valuable bioproducts, biomaterials, and bioenergy. Their versatility allows them to thrive in various wastewaters, facilitating effective contaminant removal. This study also investigates the application of microalgae in decentralized water treatment systems (DWTSs), where the decentralized nature of these systems proves advantageous in addressing heavy metal contaminants directly at the point of generation or use. This approach holds particular significance in regions where centralized systems face obstacles due to geographical constraints, inadequate infrastructure, or financial limitations. DWTSs not only provide a decentralized solution for heavy metals removal but also prove advantageous in disaster relief scenarios and rapidly growing urban areas.

Biosorption as Technique for Remediation of Heavy Metals from Wastewater using Microbial Biosorbent

Biosorption, a sustainable technology, utilizes living or non-living organism and their derivative as sorbents for the removal of heavy metals from wastewater. This review explores the mechanisms and applications of biosorption in addressing environmental challenges posed by heavy metal contaminants. Pretreatment methods enhance biosorbent performance by modifying cell wall structures through physical and chemical alterations, increasing metal binding capacity. Immobilization techniques like cell entrapment and cross-linking improve biosorbent stability and reusability in continuous systems, offering controlled particle size and ease of biomass separation. Differential Scanning Calorimetry assesses biosorbent thermal stability, providing insights into performance under varying conditions. Non-living microorganisms present advantages for biosorption, including resilience to toxic wastes and extended storage capabilities. Economic considerations are crucial when evaluating biosorbent modifications for enhanced performance. The review show that biosorption using microbial biosorbents is a versatile and efficient method for heavy metal removal from wastewater, with applications in environmental remediation and sustainable water treatment practices. Future research should focus on novel biosorption strategies and optimization of existing techniques to effectively combat heavy metal pollution.

Microbial Strategies for Heavy Metal Removal from Industrial Wastewater

The contamination of industrial wastewater with heavy metals poses a severe environmental and public health concern. Traditional methods of heavy metal removal often prove costly and environmentally unsustainable. In this context, microbial strategies have emerged as a promising and eco-friendly approach for effective heavy metal remediation from industrial wastewater. Microorganisms, including bacteria, fungi, and algae, have developed various mechanisms to withstand and sequester heavy metals from their surroundings. This review explores the diverse microbial strategies employed in heavy metal removal, encompassing biosorption, bioaccumulation, bioprecipitation, and bioleaching. These strategies exploit microbial cell surfaces, extracellular polymeric substances, and intracellular compartments to immobilize, transform, or release heavy metals. Moreover, recent advancements in genetic engineering and biotechnology have enabled the development of tailored microbial strains with enhanced metal-removal capabilities. The application of these engineered microbes, as well as naturally occurring strains, in bioremediation processes is discussed. This review also delves into the factors influencing microbial metal removal efficiency, such as pH, temperature, metal concentration, and co-existing contaminants. Additionally, the potential drawbacks and limitations of microbial strategies, including biomass disposal and long-term performance, are addressed. As heavy metal pollution continues to be a pressing global issue, understanding and harnessing microbial strategies for heavy metal removal from industrial wastewater holds significant promise for sustainable and cost-effective remediation practices. Integrating microbial processes into existing treatment methods can offer innovative solutions to mitigate the environmental impact of heavy metal contamination, thereby safeguarding ecosystems and public health

A Study of the Suitability of Microbial Cells for the Biosorption and Bioaccumulation of Heavy Metal Removal

Heavy metal contamination in the natural environment can occur as long-term site pollution or as surges of pollutants from wastewater discharge. It is well recognized that heavy metal discharge from the metal processing industries has a negative impact on the environment. Conventional methods of heavy metal removal from aqueous solutions are not cost-effective and produce large amounts of harmful chemical sludge. A novel and alternative approach to removing heavy metals from aqueous solutions involve the biosorption of these contaminants by non-living, metabolically inert biomass that is either derived from microorganisms or plants. One of the key elements of environmental and bioresource technologies today is biosorption. Due to their high surface-to-volume ratio, wide availability, quick kinetics of adsorption and desorption, and low cost, microorganisms—more specifically, bacteria, algae, yeasts, and fungi—have attracted increasing attention as biosorbents for the removal of heavy metals. Analyzing the removal of heavy metals from aqueous solutions utilizing diverse biological components, such as fungi, algae, yeast, and bacterial biomass, is the goal of the current study. This article discusses the advantages of heavy metal removal from waste streams, gives a brief overview of the technology’s potential for biosorption and bioaccumulation, and emphasizes the undelaying features of biosorption as well as operational factors like pH, the dose required to be given, the initial concentration, temperature, the efficiency of the treatment, and its economic significance.

Potential of using jackfruit peel (Artocarpus heterophyllus) as green solution for removal of copper (II) and zinc (II) from aqueous solution: Adsorption kinetics, isotherm and thermodynamic studies

Adsorbent from agricultural waste has become a popular alternative method for heavy metal removal from aqueous solutions. The purpose of this study was to look into the feasibility of employing jackfruit peel (JP) (Artocarpus heterophyllus), a solid waste that is abundant in Malaysia, for the adsorption of Cu (II) and Zn (II) from an aqueous solution. In this work, jackfruit peels were investigated as an adsorbent with no chemical modification (JP), acidified (HJP), and base modified (NaJP) for Cu(II) and Zn(II) removal from aqueous solution by using batch-adsorption modes. Spectroscopic and electron microscopic methods were used to analyze the presence of surface functional groups such as -COOH and -OH and the morphologies of the adsorbent. Adsorption investigations were carried out by adjusting adsorbent dosage (0.10–0.50 g), solution pH (3−8), initial metal ion concentrations (20–250 mg/L), temperature (298–328 K), and contact time (0–360 min). Sorption equilibrium is quickly reached within 60 min, with a higher percentage of Cu(II) and Zn(II) removal for NaJP. Regarding the effect of initial concentration on JP, the maximum adsorption for Cu(II) and Zn(II) is at 50 mg/L and 30 mg/L, respectively. Meanwhile, for HJP, the maximum adsorption for Cu(II) and Zn(II) is at 230 mg/L and 30 mg/L, respectively. For NaJP, the maximum adsorption for Cu(II) and Zn(II) is at 20 mg/L. The pseudo-second-order model best characterized the kinetic data for both metal ions using JP, HJP, and NaJP. The experimental findings fit well with the Langmuir model in explaining the adsorption process, dominated by electrostatic interaction between the adsorbent and adsorbates, showing monolayer adsorption at the binding sites on the adsorbent's surface. It was proven that with the increase of adsorbent dosage, the percent of heavy metals removal was increased due to the increasing adsorption capability of the adsorbent. In conclusion, our findings show that jackfruit peel has the potential to remove Cu(II) and Zn(II) from an aqueous solution. The adsorption process for Cu(II) and Zn(II) was favourable in acidic conditions. Under the experimental conditions, the adsorption of Cu(II) and Zn(II) onto the surface of JP, HJP, and NaJP was exothermic and non-spontaneous. The results showed that the jackfruit peel, a waste material, has a high potential as an adsorbent for removing harmful metals such as copper and zinc from water.

Preparation of Mannitol-Modified Loofah and Its High-Efficient Adsorption of Cu(II) Ions in Aqueous Solution.

Adsorption is considered the most favorable method for heavy metal removal. In this paper, a low-cost, high-efficiency heavy metal adsorbent, mannitol-modified loofah (MML) was prepared. Some characterization methods are used to characterize the structure of MML, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The adsorption behavior of MML for Cu(II) ions was explored under different conditions, such as the amount of adsorbent, pH, initial concentration of Cu(II) ions, and adsorption time. The results indicated that the adsorption capacity of MML for Cu(II) ions was greatly improved. When the initial concentration of Cu(II) ions was 900 mg/L and the pH is 5.0, the adsorption capacity (Qe) was 888.9 mg/g at 298K, which was significantly higher than that of some other modified cellulose adsorbents. Isothermal adsorption results showed that the adsorption process was consistent with the Freundlich model. The adsorption kinetics conformed to the pseudo-second-order equation. Furthermore, the regeneration capability of MML indicates that MML is a cheap and excellent adsorbent for Cu(II) ions removal in wastewater treatment.

Removal of Cr (III) from wastewater by using raw and chemically modified sawdust and corn husk

Abstract The contamination of water resources by heavy metals (HMs), mainly introduced by anthropogenic resources, has been considered as a serious environmental issue in the recent era. Therefore, the conventional methods for heavy metal removal have various drawbacks in terms of cost, toxicity, and efficiency. The novel study investigated the biosorption intensity of raw and chemically modified sawdust (SD) and corn husk (CH) to eliminate chromium (III) from the aqueous solutions. SD and CH were used as biosorbents and were treated chemically with sulfuric acid (H2SO4), sodium hydroxide (NaOH), and detergent powder. The biosorption potential was estimated based on percentage removal efficiency (% RE) of chromium (III) and the adsorption intensity (qmax). The characterization of surface morphology and functional groups of biosorbents was studied by SEM and FTIR. Moreover, the adsorption isotherm models (Langmuir and Freundlich), kinetic models (pseudo-first-order kinetics and pseudo-second-order kinetics), and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also assessed to predict the biosorption process. The results of % RE revealed that detergent-treated SD (DTSD) and detergent-treated CH (DTCH) showed highest % RE of 9.27 ± 0.15 (%) and 99.16 ± 0.08 (%) for elimination of chromium (III), respectively. Similarly, base-treated SD (BTSD) and base-treated CH (BTCH) exhibited 95.53 ± 0.18 (%) and 92.43 ± 0.22 (%) of % RE compared with 77.87 ± 1.64 (%) and 81.96 ± 0.34 (%) removal efficiency of acid-treated SD (ATSD) and acid-treated CH (ATCH), respectively. The raw SD (RSD) and raw CH (RCH) showed lower % RE of 23.68 ± 1.52 (%) and 35.52 ± 4.74 (%) for Cr (III) removal. Further, the porosity on the biosorbent's surface and attached functional groups increased after chemical treatment and this variation resulted in increased removal efficiency after chemical treatments. The Langmuir isotherm model and the Freundlich isotherm model were employed to predict the biosorption process, and both these models are best-fitted. The pseudo-second-order kinetic model was promising representative of the biosorption data. The process was endothermic and the parameters indicated that Cr (III) biosorbtion was thermodynamically favorable. Therefore, the obtained results highlighted that detergent-treatment enhanced the % RE, and DTSD and DTCH are highly efficient biosorbents for eliminating Cr (III) from aqueous solutions. Thus, detergent-treated biosorbents are proved to be a promising sustainable, eco-friendly, and cost-effective way to treat HMs from aqueous solutions as they utilize natural agriculture waste products and also handle issues related to excessive solid waste management.

Adsorption Optimization for the Removal of Cadmium in Water by Aluminum (Hydr)oxide on Cation Exchange Resin

In this study, we prepared aluminum oxide/hydroxide on a cation exchange resin and applied it for removing Cadmium (Cd) in water. The characteristics of the synthesized materials were determined by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The Cd removal tests were conducted in both batch and continuous adsorption experiments. The maximum treatment efficiency and adsorption capacity were determined to be 99.97% and 10 mg/g material, respectively, under the optimum conditions of 10 mgCd/L, 1 g/L of material, and pH 6.54 for 70 min at room temperature. The adsorption kinetics and isotherms followed pseudo-second-order kinetics and the Freundlich isotherm model, respectively. The adsorption of Cd on the material was mainly due to physical adsorption and was an exothermic process. This study gives an alternative method for heavy metal removal from water using a new, inexpensive, and available absorbent.

Investigation of micellar‐enhanced ultrafiltration (MEUF) using rhamnolipid for heavy metal removal from desalter effluent

AbstractThe removal of heavy metals from desalter effluent is an important issue due to the toxicity of these pollutants. In this study, micellar‐enhanced ultrafiltration (MEUF) is applied for the removal of heavy metals from synthetic desalter effluent. MEUF is a process in which surfactants above their critical micellar concentration (CMC) form micelles. Micelles bind compounds with low molecular weight; then, these are rejected by a semi‐permeable membrane. Rhamnolipid is an anionic biosurfactant that has advantages such as biodegradability and low CMC. Rhamnolipid complexation with synthetic desalter effluent demonstrates high efficiency for heavy metal removal. The highest overall removal efficiency was reached at a rhamnolipid concentration of 300 mg/L with 94.07%, 81.93%, 99.81%, 76.00%, and 41.91% for Zn+2, Mg+2, Cu+2, Mn+2, and Na+, respectively. Additionally, loading capacity on rhamnolipid micelles was evaluated to have better selectivity for Mn+2 > Cu+2 > Zn+2 > Mg+2 > Na+. Also, the results showed that phenol has a significant effect on heavy metal removal, decreasing CMC, which increases micelles. Finally, the permeate flux decreases after increasing the rhamnolipid concentration due to the formation of the gel layer, creating an additional resistance to the permeate flux that goes through the membrane. This work shows that MEUF with rhamnolipid is a reliable method for heavy metal removal from desalter effluent.

Efficient removal of Cu(II) from an aqueous solution using a novel chitosan assisted EDTA-intercalated hydrotalcite-like compound composite: Preparation, characterization, and adsorption mechanism

Adsorption is recognized as one of the most promising methods for heavy metal removal from contaminated water. However, the adsorption efficiency often decreases because of easy aggregation and an inevitable certain loss of adsorbents during the adsorption process. Herein, a highly efficient chitosan (CS) assisted ethylenediaminetetraacetate-intercalated Mg-Al hydrotalcite-like compound (EDTA-HTlc) composite absorbent (CS-EDTA-HTlc) was synthesized by using a simple ion-exchange/chemical crosslinking process to remove Cu(II), used as a template heavy metal, from an aqueous solution. Characterization by FESEM, PXRD, FTIR, TG-DTG, BET specific surface area, and pore volume revealed that CS-EDTA-HTlc had a high specific surface area and many different functional groups (such as carboxyl, hydroxyl, and amino) with strong complexing ability. The adsorption capacity of CS-EDTA-HTlc for Cu(II) was investigated by varying experimental conditions such as adsorbent dosage, initial solution pH, adsorption time, initial Cu(II) concentration, and temperature. The adsorption equilibrium was reached within 120 min. The Cu(II) removal efficiency came 98% with the initial Cu(II) concentration of 200 mg·L-1 and the adsorbent dosage of 1.0 g·L-1. The adsorption kinetics and isotherms data of Cu(II) on CS-EDTA-HTlc were well described by the pseudo-second-order kinetic equation and the Freundlich model, respectively. The adsorption was a spontaneous exothermic process, and the possible adsorption mechanisms analyzed by the XPS and PXRD spectra involved the complexation of Cu(II) ions by carboxyl/hydroxyl/amino groups and the isomorphic substitution of Mg(II) in brucite-like layers. The results suggest that CS-EDTA-HTlc has potential applications in natural Cu(II) contaminated wastewater treatment.

BIOSORPTION OF CU(II) IONS FROM INDUSTRIAL EFFLUENTS BY RICE HUSK: EXPERIMENT, STATISTICAL, AND ANN MODELING

Heavy metal removal from wastewater is a significant research area and recommends sustainable development. The heavy metals cause harmful health effects, increase environmental toxicity. Adsorption is a very effective method for heavy metal removal. A fixed bed for Cu(II) removal using rice hush, an agricultural waste, is reported in this paper. The study was carried out to determine the breakthrough curves with varying operating variables like influent concentration (10–30 mg/L), flow rate (10–40 ml/min), and bed height (4–10 cm) at pH 6. The variation of the process variables like influent concentration, flow rate, and bed height were investigated. The experimental data shows that adsorption capacity increases with the rise of influent concentration. The maximum value of adsorption capacity is 10.93 mg/g at a flow rate of 10 ml/min, bed height 4 cm, and influent concentration 30 mg/L. The applicability of the MLR and ANN modeling has also been successfully carried out. ANN has better predictability than MLR. The findings revealed that rice husk could be used to treat copper-containing industrial effluents.

Iron amended gravity-driven membrane (IGDM) system for heavy-metal-containing groundwater treatment

Gravity-driven membrane (GDM) system is a low-maintenance ultrafiltration system for decentralized drinking water treatment. GDM shows a high removal of pathogens, but a low removal of soluble heavy metal ions. In this study, to overcome this limitation, iron nails were introduced into a GDM system (IGDM) for the purification of heavy-metal-containing groundwater. The corrosion of iron nails continuously occurred in the influent, and rust particles were produced to remove heavy metal ions. The results suggested that the removal of As(V), Pb(Ⅱ), and Cd(Ⅱ) were all higher than 90% in the IGDM system; these removal efficiencies could be maintained because of the abundance of iron nails and the continuous formation of fresh rust. During the filtration, rust particles were partly deposited on the membrane surface, and the thickness of the cake layer in the IGDM correspondingly increased by 143% compared with that in the control GDM. The deposited rust had an inhibitory effect on the microorganisms in the cake layer, and the content of adenosine triphosphate (ATP) was reduced by 75% accordingly. However, the rust particles could adsorb organic membrane foulants, thereby alleviating organic fouling. Moreover, the bird’s-nest-like structure of the rust particles facilitated the formation of a porous cake layer, and no synergistic fouling effect of rust particles and organic foulants was observed. These positive effects offset the inhibitory effect of rusts on microorganisms and the thickness increase of the cake layer. Consequently, a stable flux of 3.5 L m-2 h-1 could still be achieved during the 105-day operation in IGDM system, although the value was 30% lower than that in the control GDM. All these results indicated that IGDM could be an economical and low-maintenance method for heavy metal removal in undeveloped areas. In addition, a house-hold scale (∼50 L d-1) IGDM was successfully operated, demonstrating the practical potential of this technology.

Unraveling the Underlying Heavy Metal Detoxification Mechanisms of Bacillus Species.

The rise of anthropogenic activities has resulted in the increasing release of various contaminants into the environment, jeopardizing fragile ecosystems in the process. Heavy metals are one of the major pollutants that contribute to the escalating problem of environmental pollution, being primarily introduced in sensitive ecological habitats through industrial effluents, wastewater, as well as sewage of various industries. Where heavy metals like zinc, copper, manganese, and nickel serve key roles in regulating different biological processes in living systems, many heavy metals can be toxic even at low concentrations, such as mercury, arsenic, cadmium, chromium, and lead, and can accumulate in intricate food chains resulting in health concerns. Over the years, many physical and chemical methods of heavy metal removal have essentially been investigated, but their disadvantages like the generation of chemical waste, complex downstream processing, and the uneconomical cost of both methods, have rendered them inefficient,. Since then, microbial bioremediation, particularly the use of bacteria, has gained attention due to the feasibility and efficiency of using them in removing heavy metals from contaminated environments. Bacteria have several methods of processing heavy metals through general resistance mechanisms, biosorption, adsorption, and efflux mechanisms. Bacillus spp. are model Gram-positive bacteria that have been studied extensively for their biosorption abilities and molecular mechanisms that enable their survival as well as their ability to remove and detoxify heavy metals. This review aims to highlight the molecular methods of Bacillus spp. in removing various heavy metals ions from contaminated environments.

Sulfur embedded on in-situ carbon nanodisc decorated on graphene sheets for efficient photocatalytic activity and capacitive deionization method for heavy metal removal

Abstract The present work describes a low cost yet versatile and efficient method for the fabrication of highly robust materials for photodegradation of dyes, removal of heavy metal ions, and capacitive method is reported to the newest. In brief, sulfur was incorporated on in-situ carbon nanodisc decorated on the surface of layered graphene sheets from natural bio-char source Musa balbisiana at low temperature by hydrothermal technique. An appropriate approach to synthesize mesoporous and high surface area of 1050 m2 g−1 in the presence of KOH at 400 °C is reported. The photo-degradation shows 4 folds higher performance better than compared to activated carbon and heavy metal removal efficiency is very superior compared to commercially available activated carbon (CAC) and in-depth kinetic, thermodynamic, and mechanism were reported. Additionally, the performance of the capacitive deionization technique very efficiently used for the rapid removal of heavy metals like Pd+2, Cd+2 is a novel study employed.

Analysis of copper removal using different seafood wastes by differential pulse voltammetry (DPV)

Current methods of heavy metal removal are shown to have several drawbacks: cost of operation, generation of toxic sludge and complicated procedures in the treatment. In this study, the ability of seafood waste as a sustainable biosorbent was investigated. Three commonly consumed seafood wastes in Malaysia were chosen for this study: crab shells, prawn shells and cockle shells. This study aimed to determine the differences in copper removal between crab, prawn and cockle shells at fixed concentrations and weights of shells. Differential pulse voltammetry using a modified screen-printed electrode was used to determine the concentration of copper for each waste sample. Removal of copper was first observed at different shell weights between 20 and 100 mg and at a fixed copper concentration of 20 ppm. Shell weights with the highest removal, 20 mg and 40 mg, were then used for further observation at concentrations between 1-20 ppm. At a weight of 20 mg, prawn shells showed the highest removal percentage of copper at 34.40% while crab shells and cockle shells showed the highest removal percentage of 31.22% and 12.78%, respectively. This was likely due to the presence of calcium carbonate and chitin as the main component in crab and prawn shells. Cockle shells showed low removal efficiency under these conditions. In conclusion, untreated crab shells and prawn shells were shown to successfully remove copper in water.

Adsorption of Mercury(II) Ion in Aqueous Solution by Using Bentonite-Based Monolith

The removal of mercury from the waterbody remains a severe challenge in ensuring environmental safety due to its highly toxic and non-biodegradable properties. Adsorption is an evidently effective method for heavy metal removal in water. This research aims to study the mercury (II) ion adsorption behavior in aqueous solution onto extruded natural bentonite in monolithic structure, bentonite-based monolith (BBM) adsorbent. BBM was characterized by XRD, BET, and SEM, the results verify BBM could improve adsorption performance assumed on its structure. Adsorption efficiency, isotherm model, and adsorption kinetic were investigated. Experiments were performed in a lab-scale batch reactor with mercury solution concentration varied from 1 to 5 mg/L. The maximum adsorption efficiency discovered to be 63,9%. The experimental data fitted well to Langmuir isotherm (non-linear) and kinetic model pseudo first order (non-linear), revealing the maximum monolayer capacity (Qo) of BBM to be 0,187 mg/g with Langmuir constants KL and aL are 0,215 L/g dan 1,151 L/mg respectively. These value confirms that BBM adsorbent encompasses tremendous potential for mercury (II) ion removal in a solution.

Restoration of heavy metal-contaminated soil and water through biosorbents: A review of current understanding and future challenges.

Heavy metal pollution in soil and water is a potential threat to human health as it renders food quality substandard. Different biosorbents such as microbial and agricultural biomass have been exploited for heavy metal immobilization in soil and sorptive removal in waters. Biosorption is an effective and sustainable method for heavy metal removal in soil and water, but the inherent challenges are to find cheap, selective, robust, and cost-effective bioadsorbents. Microbial and agricultural biomass and their modified forms such as nanocomposites and carbonaceous materials (viz., biochar, nanobiochar, biocarbon), might be useful for sequestration of heavy metals in soil via adsorption, ion exchange, complexation, precipitation, and enzymatic transformation mechanisms. In this review, potential biosorbents and their metal removal capacity in soil and water are discussed. The microbial adsorbents and modified composites of agricultural biomasses show improved performance, stability, reusability, and effectively immobilize heavy metals from soil and water. In the future, researchers may consider the modified composites, encapsulated biosorbents for soil and water remediation.

Heavy metal water pollution: A fresh look about hazards, novel and conventional remediation methods

Abstract Water pollution is one of the global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water pollutants. In this work, we discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal. Anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in aquatic environments. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, mercury, and arsenic, are outlined. We also give some perspectives about several techniques used to detect heavy metals, as well as about the factors that could affect the contaminant removal. The advantages and drawbacks of conventional and non-conventional heavy metal removal methods are critically discussed, given particular attention to those related to adsorption, nanostructured materials and plant-mediated remediation. Some of the commercial products currently used to eliminate heavy metals from water are also listed. Finally, we point out some the requirements and opportunities linked to developing efficient methods for heavy metal removal, such as the ones that exploit nanotechnologies.

Low-Cost magnetic adsorbent for efficient Cu(II) removal from water

Selective adsorption using magnetic adsorbent is supposed as one of the most effective methods for heavy metal removal from water for the advantage of efficient solid-liquid separation. However, the application of this technique is hindered by the high cost, unfavorable environmental effects of the chemical synthesis of magnetic adsorbents. In this study, the industrial waste coal-fly-ash magnetic sphere (CMS) were carefully processed to prepare cheap and green magnetic core material. Then, a composite bioadsorbent using CMS as core and chitosan (CS) as the shell (CMS@CS for short) was fabricated via an extrusion-dripping method. Structural investigations indicate that the obtained CMS@CS samples are hollow microsphere with a solid wall or porous solid microsphere depending on the preparation conditions. CMS particles are evenly distributed in both microspheres. The porous sample has an 81.49 m2 g−1 special surface area, 96 times larger than the hollow. The highest Cu(II) adsorption of the porous sample is measured as 22.41 mg g−1, 3.6 times larger than that of the hollow. The Cu(II) adsorption of the CMS@CS samples is closely related to the internal structure, surface chemical modification, and solution pH. The adsorption mechanism could be explained by a two-step procedure model. The CMS@CS adsorbents have an average magnetism of 10.07 emu g−1, thus could be magnetically separated efficiently. The density of CMS@CS is tested as 1.45–1.65 g cm−3. A similar density with water would improve its suspend ability in the water. The used CMS@CS adsorbent could be recycled several times after appropriate treatment.