Heavy Metal Pollution In Water Research Articles

Application and mechanism of carbonate material in the treatment of heavy metal pollution: a review.

Among the many heavy metal pollution treatment agents, carbonate materials show strong flexibility and versatility by virtue of their high adsorption capacity for heavy metals and the characteristics of multiple and simple modification methods. It shows good potential for development. This review summarizes the application of carbonate materials in the treatment of heavy metal pollution according to the research of other scholars. It mainly relates to the application of surface-modified, activated, and nano-sized carbonate materials in the treatment of heavy metal pollution in water. Natural carbonate minerals and composite carbonate minerals solidify and stabilize heavy metals in soil. Solidification of heavy metals in hazardous waste solids is by MICP. There are four aspects of calcium carbonate oligomers curing heavy metals in fly ash from waste incineration. The mechanism of treating heavy metals by carbonate in different media was discussed. However, in the complex environment where multiple types of pollutants coexist, questions on how to maintain the efficient processing capacity of carbonate materials and how to use MICP to integrate heavy metal fixation and seepage prevention in solid waste base under complex and changeable natural environment deserve our further consideration. In addition, the use of carbonate materials for the purification of trace radioactive wastewater and the safe treatment of trace radioactive solid waste are also worthy of further exploration.

APPLICATION OF BIOREMEDIATION IN MITIGATION OF HEAVY METAL STRESS ON PLANTS

Heavy metals are toxic metals which are persistent in nature due to their nondegradable nature.Due to increase in industrialization and urbanization heavy metals are being added to theenvironment and consequently causing heavy metal pollution of water and soil. These heavy metals cause significant stress on crop plants and effect various parameters such as growth and yield. Manymethods like physical, chemical and biological methods are available to degrade these heavymetals. Recently, bioremediation is being widely used because of its cost-effective andenvironment friendly approach. Bioremediation is a biological process which makes use ofmicroorganisms to remove hazardous substances or environmental pollutants from air, water,soil, industrial effluents etc. Bacteria and fungi are mostly employed for bioremediation.These organisms are genetically engineered for effective use in bioremediation. This not onlydiscussed about the importance of bacteria for bioremediation of heavy metals but alsodiscussed about the challenges and limitations of bacteria for bioremediation. In this chapter, a variety of mechanisms responsible for adaptation of microorganisms to high heavy metal concentrations, e.g. metal sorption, uptake and accumulation, extracellular precipitation and enzymatic oxidation or reduction, will be reported. Moreover, molecular mechanisms responsible for their metal tolerance will be described.

Decoration of dandelion-like manganese-doped iron oxide microflowers on plasma-treated biochar for alleviation of heavy metal pollution in water

Carbon-based biowaste incorporated with inorganic oxides as a composite is an enticing option to mitigate heavy metal pollution in water resources due to its more economical and efficient performance. With this in mind, we constructed manganese-doped iron oxide microflowers resembling the dandelion-like structure on the surface of cold plasma-treated carbonized rice husk (MnFe2O3/PCRH). The prepared composite exhibited 45% and 19% higher removal rates for Cu2+ and Cd2+, respectively than the pristine CRH. The MnFe2O3/PCRH composite was characterized using XRD, FTIR, FESEM, EDX, HR-TEM, XPS, BET, TGA, and zeta potential, while the adsorption capacities were investigated as a function of pH, time, and initial concentration in batch trials. As for the kinetics, the pseudo-second-order was the rate-limiting over the pseudo-first-order and Elovich model, demonstrating that the chemisorption process governed the adsorption of Cu2+ and Cd2+. Additionally, the maximum adsorption capacities of the MnFe2O3/PCRH were found to be 122.8 and 102.5 mg/g for Cu2+ and Cd2+, respectively. Based on thorough examinations by FESEM-EDS, FTIR, and XPS, the possible mechanisms for the adsorption can be ascribed to surface complexation by oxygen-containing groups, a dissolution-precipitation of the ions with –OH groups, electrostatic attraction between metal ions and the adsorbent's partially charged surface, coordination of Cu2+ and Cd2+ with π electrons by aromatic/graphitic carbon in the MnFe2O3/PCRH, and pore filling and diffusion. Lastly, the adsorption efficiencies were maintained at about 70% of its initial adsorption even after five adsorption-desorption cycles, displaying its remarkable stability and reusability.

Polyamidoamine dendrimers modified MXene and its high-performance adsorption behavior for Cr(VI)

Heavy metal pollution of water is a worldwide problem. The enticing characteristics exhibited by transition metal carbides (MXene) render it a good choiceas an adsorbent for removal of water pollutants. However, the limited functional group diversity and number, as well as the inadequate stability of MXene, impose limitations on its suitability for the adsorption of specific target metal ions (e.g., Hexavalent Cr(VI)). Herein, polyamidoamine (PAMAM) dendrimers, namely hyperbranched surfactant polymers, are employed to modify MXene, enhancing its surface functional group diversity and number. The presence of abundant –NH2 groups on the surface of PAMAM-modified MXene greatly enhances the adsorption capacity for Cr(VI). The pseudo-second order kinetic model and Langmuir isotherm model are suitable for describing the adsorption process. According to the Langmuir isotherm model, the maximum adsorption capacity (qm) can reach approximately 318 mg·g−1. Additionally, this adsorbent also has an excellent adsorption selectability for Cr(VI) from coexistent cations solution. Through the mechanisms of electrostatic attraction, reduction, covalent bonds, and chelation interaction, the high-performance adsorption for Cr(VI) can be achieved. Notably, the presence of PAMAM polymer as a protector ensures good stability of the composite adsorbent throughout adsorption/desorption cycle. This work provides deep insights into the advancement of highly efficient MXene-based adsorbents for water purification applications.

Using neutron activation to assess heavy metal pollution in water and sediment along Savannah River.

A comprehensive study was conducted to assess heavy elemental pollution in the Savannah River, which flows through diverse landscapes encompassing agricultural, industrial, and commercial zones in South Carolina and Georgia. The investigation focused on the impacts of various anthropogenic activities on the river, potentially harming human health and aquatic ecosystems. Thirty samples, collected from the beginning of the Savannah River at Lake Hartwell to the Savannah River estuary near the Atlantic Ocean, were analyzed using Instrumental Neutron Activation Analysis. In regions of intense industrial activities, water samples exhibited elevated concentrations of elements such as Al (0.04-1.99 mg/L), Mg (0.4-5.5 mg/L), Ba (0.08-2.8 mg/L), Zn (0.017-0.9 mg/L), Cr (0.005-1.5 mg/L), and Fe (2.8-110.13 mg/L). Similarly, sediment samples near industrial areas also exhibited enhanced concentrations of heavy elements like Cr, Zr, Rb, Co, Zn, Mg, Mn, and Al. The outcome of this study has identified a spatial trend along the Savannah River, revealing major elements responsible for pollution that could disrupt the ecological environment and potentially impact human health.

Seasonal Monitoring of Heavy Metal Pollution in Water and Zebra Mussels Dreissena polymorpha as a Potential Bioindicator Species from Lake Habitat.

In aquatic ecosystem, metal pollution is an important environmental hazard. Mussels as a bioindicator species are often used for assessment the presence of potentially toxic metals. Hence, the present study aimed to assess the effect of seasonal variations on some heavy metals (Cd, Cr, Pb, As, Zn and Cu) accumulation in water and Dreissena polymorpha from lake habitat. Our result indicated that Zn accumulated at a very high level in the zebra mussels while As accumulated at a high level in water samples. Seasonal variations significantly affected Cu concentration in the water samples (P < 0.05) while Cr concentration in the mussel samples was significantly affected by seasonal variations (P < 0.05). According to the water analysis, mean concentrations of metals are below the maximum limits established by the World Health Organization and USEPA, except As. Overall, our data emphasize anthropogenic pollution in the Turkish aquatic environment and confirm the use of D. polymorpha as a prospective biomonitor for metal polluted sites'.

Environmental applications of lignin-based hydrogels for Cu remediation in water and soil: adsorption mechanisms and passivation effects

Heavy metal pollution, particularly the excessive release of copper (Cu), is an urgent environmental concern. In this study, sodium lignosulfonate/carboxymethyl sa-son seed gum (SL-Cg-g-PAA) designed for remediation of Cu-contaminated water and soil was successfully synthesized through a free radical polymerization method using lignin as a raw material. This hydrogel exhibits remarkable Cu adsorption capability when applied to water, with a maximum adsorption capacity reaching 172.41 mg/g. Important adsorption mechanisms include surface complexation and electrostatic attraction between Cu(Ⅱ) and oxygen-containing functional groups (–OH, –COOH), as well as cation exchange involving –COONa and –SO3Na. Furthermore, SL/Cg-g-PAA effectively mitigated the bioavailability of heavy metals within soil matrices, as evidenced by a notable 14.1% reduction in DTPA extracted state Cu (DTPA-Cu) content in the S4 treatment (0.7% SL/Cg-g-PAA) compared to the control group. Concurrently, the Cu content in both the leaves and roots of pakchoi exhibited substantial decreases of 55.19% and 36.49%, respectively. These effects can be attributed to the precipitation and complexation reactions facilitated by the hydrogel. In summary, this composite hydrogel is highly promising for effective remediation of heavy metal pollution in water and soil, with a particular capability for the immobilization of Cu(Ⅱ) and reduction of its adverse effects on ecosystems.

Adsorption and Kinetics Modelling for Chromium (Cr6+) Uptake from Contaminated Water by Quaternized Date Palm Waste

The pervasive challenge of heavy metal pollution in water necessitates urgent interventions to mitigate chromium contamination. It poses significant threats to human health, aquatic ecosystems, and the environment. This research delves into the potential of date palm waste as a precursor of adsorbent for extraction of chromium from contaminated water, underscoring its potential in heavy metal remediation. Date palm waste, traditionally regarded as agricultural waste, underwent modification employing N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride resulting in quaternized date palm waste (QDPW) as a prospective adsorbent for chromium extraction. The characterization techniques, including FTIR, SEM/EDX, BET, XRD, TGA/DTA, and element analysis, were employed to examine the structural and surface properties of both DPW and QDPW fibers. Optimal chromium uptake was achieved at a solution pH 6.5 over two hours, with a peak removal efficiency of 88% and an adsorption capacity of 22.26 mg/g. The equilibrium isotherms studies are consistent with Langmuir, Redlich-Peterson, and Sips isotherms, presenting a coefficient of determination (R2) of 0.989, 0.981, and 0.983, respectively. Moreover, the pseudo-second-order model was mostly aligned with the kinetics data with R2 value of 0.999. These findings showed that the quaternized date palm waste can be considered a good option to recycle the date palm waste and reduce the environmental threats in aqueous solution.

DMF promoted embedded of melamine inside HKUST-1 for efficient Hg(II) adsorption with regenerability

In response to the growing problem of Hg(II) pollution in water environment, highly efficient HKUST-1@melamine adsorbent for Hg(II) removal was synthesized by in-situ growth post-synthesis modification method. Under the regulation of DMF, melamine embedded inside the HKUST-1 pore, which guaranteed the high loading rate. Based on theoretical calculation, DMF lowered the energy barrier for melamine to enter the HKUST-1 pore (2.79 eV to 0.21 eV). Meanwhile, water stability and skeleton structure were also be strengthened. The –NH2 on melamine in the pores would coordinate with Hg(II), and the corresponding Eads of the composite with Hg(II) was calculated −3.49 eV, confirming the spontaneous adsorption reaction. Under the optimal conditions, HKUST-1@melamine showed the best adsorption of Hg(II) with a removal rate of 99.41 % within 90 min. The maximum adsorption capacity qm of 1557.38 mg/g, which was several times more than the existing MOF-based adsorbents. And the good selectivity and anti-interference realized the following practical application in real samples. In addition, the material achieved 85.3 % of qm after 4 regeneration cycles with 5 % thiourea. This research would provide a theoretical basis for rapid and efficient nanomaterials-based treatment of heavy metals pollution in water.

Biochar supported nanoscale zerovalent iron-calcium alginate composite for simultaneous removal of Mn(II) and Cr(VI) from wastewater: Sorption performance and mechanisms

Heavy metal pollution in water caused by industrial activities has become a global environmental issue. Among them, manganese mining and smelting activities have caused the combined pollution of Cr(VI) and Mn(II) in water, posing a serious ecotoxicological risk to ecological environments and human health. To efficiently remove Cr(VI) and Mn(II) from wastewater, a novel biochar supported nanoscale zerovalent iron-calcium alginate composite (CA/nZVI/RSBC) was synthesized by liquid-phase reduction and calcium alginate embedding methods. The adsorption performance and mechanisms of Cr(VI) and Mn(II) by CA/nZVI/RSBC were investigated. The maximum adsorption capacities of Cr(VI) and Mn(II) onto CA/nZVI/RSBC fitted by the Langmuir model were 5.38 and 39.78 mg/g, respectively, which were much higher than the pristine biochar. The iron release from CA/nZVI/RSBC was comparatively lower than that of nZVI/RSBC. Mn(II) presence enhanced the reduction of Cr(VI) by CA/nZVI/RSBC. The results of XRD, XPS, and site energy distribution analysis indicated that redox was the predominant mechanism of Cr(VI) adsorption, while electrostatic attraction dominated Mn(II) adsorption. This study provides a novel alternative way for the simultaneous removal of Cr(VI) and Mn(II) in wastewater.

Research Progress of Treatment Method of Metal Ion in Wastewater

Along with the rapid development of urbanization in China, a series of environmental problems have accompanied, especially industrial effluents containing heavy metals such as lead, cadmium, mercury, etc., which have caused great damage to water, soil and earth, and have caused great harm to human health. In this article, new processes such as adsorption, membrane separation, chemical precipitation, ion exchange, bio-adsorption, and bio-reduction are introduced. The technology has shown excellent results in a variety of working conditions, opening up new ways for the treatment of heavy metal pollution in water. The development of this topic is of great and urgent practical significance for the protection of ecological environment and the promotion of sustainable development in China.

Research Progress of Biochar for Water Pollution Control

As an emerging carbon material, biochar has received great attention from scholars in recent years. This paper focuses on the application of three kinds of biochar in water pollution control engineering and their degree of control on organic matter and heavy metal pollution in water. The paper discusses sludge-based biochar, agricultural biomass matrix biochar, and clay mineral/biochar composites. The paper concludes that most biochar materials are at the experimental exploratory research stage and there is limited research on their commercial applications. The paper describes the mechanisms of how biochar can control organic and heavy metal pollution and discusses the advantages and limitations of biochar in controlling these two types of pollutants and the future direction of biochar. The aim of this paper is to help researchers understand the role of biochar in water pollution control engineering and to establish the relevant knowledge framework and logic more effectively. It is hoped that after reading this paper, readers will be able to explore and discover suitable biochar materials or biochar composites for water pollution control engineering.

Design and construction of SnIn4S8/Cd0.5Zn0.5S heterostructure photocatalyst for efficient Cr(VI) reduction

The development of highly competent and economical photocatalysts for competent erasure of heavy metal pollutants in water is of momentous import but still a significant challenge. Herein, 3D/0D SnIn4S8/Cd0.5Zn0.5S heterostructure photocatalyst was resoundingly fabricated through integrating Cd0.5Zn0.5S nanoparticles on the surface of SnIn4S8 microsphere via a simple solvothermal method and applied to high efficiency photoreduction Cr(VI). The fabricated SnIn4S8/Cd0.5Zn0.5S with optimized composition ratio achieves the exceptional reduction Cr(VI) property and the photoreduction efficiency of 20 % SnIn4S8/Cd0.5Zn0.5S can reach 91.1 % within 30 min visible light illumination. The prominent photocatalytic efficiency comes from the intimate contact of heterostructure interface, which effectively expedites the separation and migration of carrier and inhibits the photocorrosion of photocatalyst. This work provides a promising photocatalyst for water environment remediation, and promotes the exploration of heterostructure photocatalyst for wastewater purification.

Phycoremediation of Cadmium using Chlorella vulgaris in Photobioreactor

Chlorella vulgaris had the ability to accumulate heavy metals in their bodies, so they could be used as biosorbent in handling heavy metal pollution in waters. The effectiveness of C. vulgaris in the remediation of cadmium (Cd) would be tested in this present study. C. vulgaris were cultured for 14 days in the photobioreactor which was an enclosed chamber that was fully aerated and illuminated with LED lamps. Cadmium with concentrations of 0 (control), 0.05, and 0.1 ppm was mixed with C. vulgaris growth medium. The number of C. vulgaris cells was counted every 3.5 days using a hemocytometer to determine the growth condition. Metal concentrations were also measured on days 0, 7, and 14 using atomic absorption spectrophotometry (AAS). C. vulgaris was able to reduce cadmium levels up to 98%. The decrease in cadmium levels with the highest efficiency occurred at a cadmium concentration of 0.05 ppm.

Regulating ordered structure and multi-functions of zeolite aerogels for solar steam generation and heavy metal ion adsorption

The interfacial solar steam generation (ISSG) is considered to be a promising technology to alleviate the water crisis. However, the salt accumulation on the solar evaporators and the heavy metal pollution in water hinder the commercial potential and practical application of the evaporators. Herein, a solar evaporator with high salt resistance and efficient heavy metal wastewater treatment is designed using commercial artificial zeolite as matrix, modified zeolite (MZ), cellulose acetate (CA), and carbon nanotubes (CNTs), named as MZPC@CNTs. The applicability of the developed MZPC@CNTs in water evaporation, seawater desalination, heavy metal wastewater treatment, and water purification of organic pollutants is studied systematically. Through the regulation of the ordered structure and multiple functions, the obtained MZPC@CNTs based aerogel shows an evaporation rate of 1.72 kg m-2 h−1 with a corresponding efficiency of 95.33% under 1 sun radiation. In addition, the MZPC @CNTs aerogel also exhibits excellent ion desalination performance and excellent salt resistance towards the purification of heavy metal-contaminated wastewater. This solar evaporator has the advantages of simple preparation, low cost, and stable desalination performance, and reveals great potential in alleviating the shortage of global freshwater resources.

Investigation of Some Heavy Metal Resistance Genes in E.coli Isolated from Shrimp and Mussels

One of the biggest problems in the modern world is environmental pollution. All organisms are affected by the resulting pollution, albeit at different levels. One of the most important causes of pollution is the stable and non-perishable compounds formed due to heavy metals used in a wide range of environments. Heavy metal pollution, especially in the seas, causes cumulative accumulations in aquatic life, food and other products obtained from aquatic life, in living things that consume these products, and related diseases. The most critical sign of heavy metal pollution in water is the resistance formed against heavy metals in bacteria living in these waters. To determine the resistance to heavy metals in bacteria, the presence of resistance to Copper, Mercury and Manganese heavy metals in E. coli isolated from 18 mussels and 16 shrimps was genotypically investigated. For this purpose, the presence of pcoR genes for the determination of copper resistance, merA for the determination of mercury resistance, and mntR for the determination of manganese resistance was investigated in both plasmid and genomic DNA. As a result of the study, resistance genes were detected against heavy metals in 31 (91.17%) of 34 E. coli isolates examined. The presence of the pcoR gene (copper resistance) was found in 2 isolates (5.88%), the merA gene (mercury resistance) in only one isolate (2.94%) and the mntR gene (manganese resistance) in 8 isolates (23.52%). While pcoR and merA genes were not observed together in any isolates, pcoR and mntR genes were detected together in the genetic material of 10 isolates (29.41%). In comparison, mntR and merA genes were detected together in the genetic material of 7 isolates (20.58%). In 3 samples, all of the resistance genes against heavy metals were detected (8.82%).

Ni-Fe Alloy Coatings Prepared via Jet Electrodeposition for the Optimization of the Electrochemical Detection Performance of Laser-Induced Graphene for Pb(II)

Heavy metal pollution in water, particularly Pb ion pollution, has seriously threatened human life and health. Therefore, the manufacture of efficient and sensitive heavy metal ion detection materials is essential. The objective of this study was to improve the electrochemical detection performance of laser-induced graphene (LIG) for Pb(II). Considering the excellent ion affinity and high activity of transition metals, Ni-Fe alloy coatings were prepared on the surface of LIG through jet electrodeposition. The prepared LIG and Ni-Fe/LIG were qualitatively analyzed through Raman spectrometry, X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The surface micromorphologies, charge transfer capabilities, and electrochemically active surface areas of LIG and Ni-Fe/LIG were characterized. The detection range and limit of detection (LOD) of Pb(II) for LIG and Ni-Fe /LIG as electrochemical sensors were analyzed. Results showed that compared with LIG, Ni-Fe/LIG had more surface active sites, a higher charge transfer capability, and a larger electrochemically active surface area that reached 0.828 cm2. Ni-Fe/LIG had a detection range of 20–1200 µg/L and an LOD of as low as 0.771 µg/L. Ni-Fe/LIG demonstrated a better electrochemical detection performance for Pb(II) than LIG when used as an electrochemical sensor.

Stability and biomineralization of cadmium sulfide nanoparticles biosynthesized by the bacterium Rhodopseudomonas palustris under light

Cadmium (Cd) pollution is regarded as a potent problem due to its hazard risks to the environment, making it crucial to be removed. Compared to the physicochemical techniques (e.g., adsorption, ion exchange, etc.), bioremediation is a promising alternative technology for Cd removal, due to its cost-effectiveness, and eco-friendliness. Among them, microbial-induced cadmium sulfide mineralization (Bio-CdS NPs) is a process of great significance for environmental protection. In this study, microbial cysteine desulfhydrase coupled with cysteine acted as a strategy for Bio-CdS NPs by Rhodopseudomonas palustris. The synthesis, activity, and stability of Bio-CdS NPs-R. palustris hybrid was explored under different light conditions. Results show that low light (LL) intensity could promote cysteine desulfhydrase activities to accelerate hybrid synthesis, and facilitated bacterial growth by the photo-induced electrons of Bio-CdS NPs. Additionally, the enhanced cysteine desulfhydrase activity effectively alleviated high Cd-stress. However, the hybrid rapidly dissolved under changed environmental factors, including light intensity and oxygen. The factors affecting the dissolution were ranked as follows: darkness/microaerobic ≈ darkness/aerobic < LL/microaerobic < high light (HL)/microaerobic < LL/aerobic < HL/aerobic. The research provides a deeper understanding of Bio-CdS NPs-bacteria hybird synthesis and its stability in Cd-polluted water, allowing advanced bioremediation treatment of heavy metal pollution in water.

Metabolic Plasticity Endows Mixotrophic Organisms with High Tolerance to Cadmium and Special Potential for Recovering Cadmium-Contaminated Aquatic Environment.

Heavy metal pollution in waters causes serious stress to aquatic ecosystems. Several autotrophs with strong tolerance are extensively used to adsorb heavy metals, but their use may be limited by the specific conditions of polluted waters due to their single nutrition mode. By contrast, mixotrophs possess strong environmental adaptability due to their plastic metabolic modes. However, studies focusing on mixotroph's resistance and its underlying mechanism in response to heavy metals and their bioremediation potentials are currently lacking. In this study, we investigated the population, phytophysiological, and transcriptomic (RNA-Seq) responses of a typical and common mixotrophic organism, Ochromonas, to cadmium exposure and then evaluated their capacity to remove cadmium under mixotrophic condition. Compared with autotrophy, mixotrophic Ochromonas enhanced photosynthetic performances under short-time cadmium exposure and subsequently shifted to stronger resistance with increasing exposure time. Transcriptomic analyses suggested that the genes related to photosynthesis, ATP production, ECM components, and scavenging of reactive oxygen species and damaged organelles were upregulated to boost mixotrophic Ochromonas resistance to cadmium. Consequently, the harm of metal exposure was eventually reduced and cellular stability was maintained. Approximately, 70% of cadmium at 2.4 mg L-1 cadmium was removed by mixotrophic Ochromonas in the end, benefiting from upregulated genes associated with the transport of metal ions. Hence, mixotrophic Ochromonas tolerance to cadmium can be attributed to multiple pathways of energy metabolism and effective transport of metal ions. Collectively, this study advanced a better understanding of the unique mechanism of heavy metal resistance in mixotrophs and their potential use in recovering cadmium-contaminated aquatic ecosystems. IMPORTANCE Mixotrophs widely living in aquatic ecosystems possess unique ecological roles and strong environmental adaptability due to their plastic metabolic modes; however, little is known about their underlying resistance mechanism and bioremediation potential in response to environmental stresses. For the first time, this work investigated how mixotrophs respond to metal pollutants through physiological, population dynamics, and transcriptional regulation, and highlighted the unique underlying mechanism of mixotrophs to resist and remove heavy metal, thereby advancing our understanding of the potentials of mixotrophs in recovering metal-contaminated aquatic environments. These unique properties in mixotrophs are essential for the long-term functional stability of aquatic ecosystems.

Calcium alginate-nZVI-biochar for removal of Pb/Zn/Cd in water: Insights into governing mechanisms and performance

Heavy metals pollution in water caused by the intensification of industrial processes and human activities has attracted worldwide attention. Finding an environmental-friendly and efficient remediation method is in need. In this study, the calcium alginate entrapment and liquid-phase reduction method were used to prepare calcium alginate-nZVI-biochar composite (CANRC), which was firstly used to remove Pb2+, Zn2+, and Cd2+ in water. The effects of pyrolysis temperature, solution pH, and coexisting ions, etc. during adsorption processes were explored. Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the physicochemical properties of CANRC before and after adsorption. Different adsorption models and site energy analysis were used to analyze the possible mechanisms. The results showed that CANRC prepared at 300 °C and a 5 wt% Fe loading ratio had the maximum adsorption capacities with a dosage of 2.5 g/L and pH = 5.0– 6.0. The adsorption process was more in line with the Langmuir isotherm model dominated by monolayer adsorption. The maximum adsorption capacities of Pb2+, Zn2+, and Cd2+ were 247.99, 71.77, and 47.27 mg/g, respectively. Site energy analysis combined with XRD and XPS analysis indicated that surface complexation and precipitation were the main adsorption mechanisms. This study provides an alternative way for the removal of heavy metals from water.