Removal Efficiency Of Heavy Metals Research Articles

Towards the Sustainable Removal of Heavy Metals from Wastewater Using Arthrospira platensis: A Laboratory-Scale Approach in the Context of a Green Circular Economy

The use of living Arthrospira platensis (A. platensis) cultures emerges as a promising green solution for the bioremediation of water contaminated by toxic metal waste. The scope of the present study is to evaluate the microalga’s potential in heavy metal remediation, in the case of multi-metal-treated (multi-MT) systems. For this reason, A. platensis cultures were exposed to mono- and multi-metal solutions of Cu, Cd, Ni, Pb, and Zn, and their metal adsorption ability was investigated. The heavy metal removal efficiency of A. platensis cultures was evaluated using atomic absorption spectroscopy (AAS). Additionally, the cultures were examined using Fourier transform infrared (FTIR) spectroscopy, Near-Infrared (NIR) Spectroscopy, UV-Vis spectrophotometry, and optical microscopy, together with pH and electrical conductivity (EC) measurements to evaluate the quality of the cultures and the changes induced by heavy metal stress. The results showed that metal removal is still efficient in multi-MT cultures. In particular, Cu, Cd, Pb, and Zn removal of multi-MT cultures is elevated or relative to the respective removal of the mono-metal-treated (mono-MT) cultures, showing a synergistic or cooperative interaction between the metals, while the removal of Ni of multi-MT cultures decreased compared to Ni of mono-MT cultures, showing an antagonistic interaction to the other metals. The study shows that A. platensis is considered an effective microalga toward the bioremediation of multi-metal polluted cultures.

The Effectiveness of an Anoxic-Oxic-Anoxic-Oxic Sequencing Batch Reactor System (A2/O2-SBR) to Treat Electroplating Wastewater and the Bacterial Community within the System

This study presents an examination of the effectiveness of an anoxic-oxic-anoxic-oxic sequencing batch reactor (A2/O2-SBR) for treating electroplating wastewater (EPWW). The A2/O2-SBR was monitored for 60 days and the bacterial composition in the treatment system was determined. The system consisted of four reactors, which had the following anoxic/oxic ratios: reactor-I, 0:9 h; reactor-II, 2:7 h; reactor-III, 4.5:4.5 h; and reactor-IV, 7:2 h. The combined cycle time of the reactors was 12 h, the hydraulic retention time (HRT) was five days, and the total volume of mixed liquor suspended solids (MLSS) was 2,000 mg/L. The results demonstrate the importance of an anoxic period for the treatment of heavy metals. Most of the ammonium nitrogen (NH4+-N), Total Kjeldahl nitrogen (TKN), and total nitrogen (TN) were removed during the oxic period. However, as the anoxic period increased, the amounts of TKN, nitrite nitrogen (NO2--N), nitrate nitrogen (NO3--N), and TN declined. Reactor-IV showed a high removal efficiency for heavy metals (Zn2+, 89.74%; Cd2+, 81.37%), TKN (89.20%), and TN (84.25%), and also effectively treated NH4+-N (78.84%), biochemical oxygen demand (BOD5; 93.5%), and chemical oxygen demand (COD; 84.9%). Reactor-IV showed an appropriate difference in the dissolved oxygen (DO) concentration between the anoxic period and oxic period (2.12-2.00 mg/L). The main bacterial phyla in the treatment system were Proteobacteria, Actinobacteria, and Firmicutes, while Pseudomonas vancouverensis and Cryobacterium arcticum were the most common species. The anoxic period and bacterial community have significantly demonstrated the ability to remove Zn2+ and Cd2+ for effective treatment of EPWW.

Waste-derived substrates in vertical-flow constructed wetlands for an efficient removal of high-concentration heavy metals

ABSTRACT Contamination by heavy metals (HMs) in aquatic ecosystems is a worldwide issue. Therefore, a feasible solution is crucial for underdeveloped and developing countries. Waste-derived materials (WDMs) exhibit unique physical and chemical properties that promote diverse mechanisms for the removal of HMs in constructed wetlands (CWs). In this study, we aimed to report the removal efficiency of HMs of vertical-flow constructed wetland (VFCW) systems using different WDMs, such as clinker brick (Jhama), eggshells, and date palm fiber (DPF). Synthetic wastewater with high concentrations (3.3–61.8) mg/L of HMs (As, Cr, Cd, Pb, Fe, Zn, Cu, and Ni) was applied to the systems followed by 3 days of hydraulic retention time. The results demonstrate that removal efficiencies of HMs ranged between 94.8 and 98.7% for DPF, 95.4–98.5% for eggshells, and 79.9–92.9% for the Jhama-filled CWs, while the gravel-based systems were capable of 73–87.6% removal. Two macrophytes, Canna indica and Hymenocallis littoralis were planted in the CWs and exhibited significant accumulation of HMs in their roots. The study reports that WDMs are effective for concentrated HM removal in CWs, and macrophytes demonstrate significant phytoremediation capabilities. The findings of this study will facilitate the economically feasible and efficient design of CWs for effectively treating concentrated HMs in wastewater.

Jute-Copper Nanocomposite Embedded PSf Membrane for Sustainable and Efficient Heavy Metal Removal from Water Sources.

Numerous corporations have overlooked environmental regulations concerning wastewater treatment, leading to a worldwide issue regarding hazardous pollutant discharge, particularly dyes and heavy metal ions, into river sources. Various industries, with water, energy, and biological sectors, actively employ membranes. Membranes capable of showing flux, metal and dye sorption, and catalysis have been developed and are extensively used by functionalizing the pores of ultrafiltration, microfiltration, and nanofiltration membranes with responsive properties. The enhancement of synthetic membrane performance can be achieved by developing new polymers or modifying the surface of existing polymers. In this study, high porosity and large internal pore volume polysulfone (PSf) membrane composites were produced on a laboratory scale by adjusting the polymer coagulation conditions during the phase inversion process, incorporating copper nanoparticles for antifouling properties, and utilizing pretreated natural jute fibers. A comprehensive characterization of the composites was conducted by using FTIR, XRD, XPS, ICP-MS, and SEM techniques. To calculate their possible uses in separation and purification methods, the performance of PSf-based membrane composites was evaluated in terms of heavy metal rejection rates (%) in water.

Removal characteristics of heavy metals from polluted river water purified by hybrid constructed wetlands.

Heavy metal pollution in urban rivers has become a global issue. In this study, hybrid constructed wetlands (HCWs) were used to comprehensively evaluate the effectiveness of field wetland projects in removing heavy metals, with evaluation metrics including seasonal variations, plant contributions, and structure compositions. The experimental results showed that the synergistic system of root-microorganism-substrate formed in the combined process well realized the high efficiency of heavy metal removal, in which the removal rate in the warm season was higher than that in the cold season. The average removal rates of Cu, Zn, Cr, and Pb were 44.62%, 43.12%, 40.59% and 45.18%, respectively. In the effluent, Zn and Cr can better meet the corresponding standards of the US, EU, and CN, and the biotoxicity of Cu and Pb was also greatly reduced. Compared to Cu, Cr, and Pb, the removal of Zn was less affected by influent loads and stable removal was achieved. In HCWs, the primary contribution to heavy metal removal is attributed to sediment deposition, subsequently followed by the uptake by plant roots and stems, with adsorption onto fillers being the least significant. These results of the study show that HCWs can effectively treat heavy metal pollution in water bodies, and are a highly efficient process for ecological remediation of urban river water. Most importantly, HCWs have demonstrated strong adaptability during the operation of actual ecological restoration projects. Additionally, HCWs can adjust the component structure according to the specific conditions of the process to realize the highest efficiency, which provides a new idea for urban river ecological restoration.

Optimization of Cl and heavy metal removal during heat treatment of municipal solid waste incineration fly ash and municipal sludge after co-washing.

Heat treatment, known for its detoxification and volume reduction characteristics, is a promising technology for the management of municipal solid waste incineration fly ash (MFA) and municipal sludge (MS). This paper uses the solid residue from MFA and MS after co-washing as the raw material to study the melting properties, phase transformations, changes in Cl content, heavy metal removal efficiency, and leaching toxicity. The results indicated that co-processing of MFA and MS can effectively reduce the melting temperature. The migration of Cl elements was influenced by the CaO/(SiO2 + Al2O3) ratio and the formation of Cl-containing phases. During the heat treatment process, Cr and Ni remained relatively stable, while Zn, Pb, Cu, and Cd were affected by Cl migration. Chlorine can promote the volatilization and escape of these heavy metals, but as Cl became fixed within Ca10(SiO4)3(SO4)3Cl2 and Ca5(PO4)3Cl, the removal efficiency decreased. To achieve the highest removal rates for these elements, the addition of MFA should be limited to no more than 20%, and the CaO/(SiO2 + Al2O3) ratio should be below 2.9. After heat treatment, the leaching concentrations of Zn, Pb, Cu, Cr, Cd, and Ni met applicable standards. The findings of this study could provide a method for the treatment of MFA and MS after co-washing and can serve as guidance for heat treatment processes.

Homogeneous Crystallization of Nickel as Ni₃S₄ in a Fluidized Bed Reactor with Supersaturation Control

This study investigates the recovery of nickel sulfide (NiS) using fluidized bed homogeneous crystallization (FBHC), emphasizing the process from nucleation to crystallization. Sludge production in conventional chemical precipitation becomes a drawback in treating wastewater economically and efficiently. FBHC offers a promising alternative by minimizing sludge generation. The study examines various operational parameters, including hydraulic retention times (HRT), reflux ratio (R), initial nickel concentration, and static bed height (SBH), to optimize NiS recovery. Results show that FBHC achieves high total removal efficiency (TR) and crystallization ratio (CR), under the optimum condition of HRT = 15min, R = 8.3, initial nickel concentration = 147mg/L, and SBH = 35cm. The agglomeration of Ni(OH)2 was found to be crucial for the crystal growth during the surface oxidation of Ni3S4. This technological approach to wastewater treatment offers highly efficient heavy metal removal from wastewater.

Enhancing Tannic Acid-Arginine Complex Loading in Ultraporous PA6 Nanofibers through NH3 Foaming for Efficient Heavy Metal Removal from Textile Wastewater.

Metal-containing dyes in the textile industry release heavy metal ions into wastewater, posing significant environmental risks and complicating treatment processes. Among various removal methods, chemical adsorption through functional groups that form stable complexes is one of the most effective. Tannic acid (TA), renowned for its strong chelation of metal ions via phenolic hydroxyl groups, faces challenges in operation and recycling in its powdered form. Electrospun polyamide 6 (PA6) nanofiber membranes, characterized by high surface area and structural stability, offer a promising platform. However, achieving an optimal TA loading remains a technical hurdle for industrial applications. To address this, we developed an arginine (l-Arg) bridging strategy to enhance the TA loading on PA6 nanofibers. Additionally, we implemented an NH3 escape foaming technique to increase membrane porosity by 20% and quadruple pore size, enhancing surface roughness and resulting in a 70% increase in TA loading. The optimized adsorbent demonstrated the effective removal of various heavy metal ions, achieving over 95% removal efficiency for five different metals. Even after five adsorption-desorption cycles, the membrane retained over 92% efficiency, translating to a treatment capacity of 12.5 tons of wastewater per kilogram of foaming fiber, underscoring its potential for practical wastewater treatment applications.

Eco-Friendly Hydrogel Beads from Seashell Waste for Efficient Removal of Heavy Metals from Water.

The objective of this study is to develop a calcium carbonate-based adsorbent derived from Cellana Tramoscrica seashells, incorporated into a sodium alginate matrix (Na-Alg@CTs) to form hydrogel beads, for the efficient removal of Cu (II) and Zn (II) heavy metals from aqueous solutions. XRD, SEM/EDS, and FTIR analysis confirm the successful synthesis and characterization of the fabricated adsorbent. The adsorption study of Cu (II) and Zn (II) onto Na-Alg@CTs hydrogel beads revealed that the Langmuir model was the most suitable for characterizing the adsorption isotherms, suggesting monolayer coverage. Na-Alg@CTs exhibited a maximum Langmuir adsorption capacity of 368.58 mg/g and 1075.67 mg/g for Cu (II) and Zn (II), respectively. Additionally, the kinetics followed the pseudo-second-order model, indicating that the adsorption process is primarily governed by chemisorption. The thermodynamic study suggests that the uptake of metal ions on Na-Alg@CTs hydrogel beads is spontaneous and endothermic. The exceptional adsorption capacity, eco-friendly nature, and low-cost characteristics of Na-Alg@CTs hydrogel beads make them an ideal adsorbent for the removal of Cu (II) and Zn (II) from wastewater.

Fe3O4 nanoparticles decorated on N-doped graphene oxide nanosheets for elimination of heavy metals from industrial wastewater and desulfurization

Finding an effective and excellent pertinent single catalyst material for multipurpose application for the purification of hydrocarbons in fuels (desulfurization), and for efficient removal of heavy metals from industrial effluent is greatly endowed. In the present work, a hybrid nanocomposite of ultrafine magnetite (Fe3O4) nanoparticle embedded on the surface of in-situ nitrogen doped layered GO (NGO) sheets were fabricated by sol-gel method and treatment with microwave irradiation technique is reported for the first time. The results show a high removal efficiency of 97 % for multiple heavy metals (Pb2+, Cd2+, Cu2+, Cr+2, Mn+2etc.) in industrial effluent and as well as in synthetic water with a very good retention performance of 99 %. The composites were tested against the elimination of sulfur from thiophene is 1.495 mmol g−1 is reported high is due to coupling and coordination of nitrogen with FeO and C. Recycling studies showed that the developed composites had excellent recyclability, with <82 % removal at the 5th cycle; its feasibility was evaluated using industrial effluent water and in synthetic water. Surface phenomena studies presented here revealed that the adsorptive removal processes of heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation that showed an excellent synergism. A high stability, and retention performance is better than the pure Fe3O4 and NGO sheets. We hope that this study will motivate and give further scope for scientists working on magnetite-based graphene nanocomposites.

Monitoring and Studying the Behavior of Metals in an Industrial Wastewater Treatment Plant in Italy

Heavy metals represent a significant hazard in textile wastewater, posing a considerable risk to both the ecosystem and human health. The objective of this study was to analyze the removal efficiency of specific heavy metals in a large wastewater treatment plant (WWTP) located in Prato (Tuscany, Italy), where the main Italian textile district is based. To achieve this, the mass balance calculation approach was employed. Therefore, two monitoring campaigns were conducted, collecting wastewater and sludge samples in some specific sections of the WWTP. The concentrations of Pb, Cd, Ni, As, and Sn were consistently below the detection limits. A good removal efficiency was determined for Zn, Cu, Ba, Crtot, and Sb, in the range of 37–79%. These metals are predominantly present in particulate form, facilitating their removal through sedimentation. Conversely, boron is largely present in the dissolved phase, resulting in its complete release through the treated effluent. Subsequently, an excellent linear correlation was identified between the input load and the contaminant load removed. This demonstrated that the plant’s efficiency remains unaffected by an increase in the input load at the observed contaminant concentrations. Finally, a probability law was identified that demonstrates an excellent degree of approximation in representing inlet metal concentrations. The findings of this study indicate that the treatment systems employed by the WWTP are capable of effectively removing heavy metals.

Harnessing microbial synergy: A comprehensive evaluation of consortia-mediated bioremediation strategies for petroleum refinery wastewater treatment

The growing global demand for energy has led to the expansion of oil and gas industries, putting our environment at risk of pollution. The unregulated discharge of petroleum refinery wastewater (PRW), accidental spills, and ineffective policies have led to severe contamination and increased environmental and health consequences making management and mitigation a priority for everyone. This study evaluated the performance of two biological treatment methods - free-cell microbial consortium and immobilized microbial system - in the remediation of PRW using physicochemical, 2,6-dichlorophenollindophenol (DCPIP), Gas chromatography (GC) and Fourier-transform infrared spectroscopy (FTIR) techniques. The effectiveness of the two microbial consortia in reducing concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in the wastewater was compared to determine the most efficient method for treating PRW. The physicochemical result revealed cocktails of contaminants while Alcaligenes faecalis strain SLW6 and strain IAM 12369, and Providencia vermicola strain OP1, showed high degradative capacities. The immobilized and free-cell microbial systems significantly reduced the concentrations of PAHs, and HMs pollutants in the wastewater, with the former showing slightly better removal efficiencies for PAHs (92.97 % vs 87.34 %), heavy metals (99.17 %), and oil weight reduction (87.76 % vs 82.25 %) after the 28-day biodegradation period respectively. GC and FTIR analyses confirmed the formation of various degraded products, demonstrating the microbial consortia's effectiveness in degrading complex organic compounds. The findings highlight the potential of microbial consortia-mediated remediation as an eco-friendly and sustainable approach for treating PRW, contributing to protecting water resources and promoting sustainable practices in the petroleum industry.

Comparative Study of Biosorption and Traditional Methods for Heavy Metal Removal from Industrial Wastewater in Panipat

In this research paper, I have thoroughy described about the topic Comparative Study of Biosorption and Traditional Methods for Heavy Metal Removal from Industrial Wastewater in Panipat.” Industrial wastewater contamination by toxic heavy metals poses a significant environmental threat globally, especially in rapidly industrializing regions like Panipat District in Haryana, India. Panipat, renowned for its extensive textile and chemical industries, generates substantial volumes of wastewater laden with heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg). Recent studies have revealed that the concentrations of these metals in Panipat's industrial effluents frequently surpass the permissible limits set by environmental regulations. Traditional methods for heavy metal removal, including chemical precipitation and ion exchange, are widely utilized but often entail high operational costs and the generation of secondary pollutants like sludge. Biosorption, an emerging and sustainable technology, offers a promising alternative by utilizing biological materials such as algae, bacteria, and agricultural waste to adsorb heavy metals from wastewater. This study aims to investigate the effectiveness, cost-effectiveness, and environmental impact of biosorption compared to traditional methods in Panipat District. By examining heavy metal removal efficiencies, conducting cost analysis, and assessing environmental implications, this research seeks to provide valuable insights into sustainable wastewater treatment practices.

Waste glass as a source for green synthesis of mesoporous adsorbent for efficient removal of heavy metals

Mesoporous analcime Adsorbent (MaA) was cogently synthesized in a hydrothermal reaction where a waste silica glass powder was mixed into NaOH solution. The satisfactory reaction properties were achieved by regulating the conditioning time (Ct), reaction temperature (Rt), and relative ratio of the reactants (Rr = SiO2:Na2O). XRF, XRD, SEM, BET, FTIR, AFM, TG and TEM analysis formed part of the selected samples. The prepared MaA adsorbent was then applied to treat Pb2+, Cd2+ and Cu2+ ions, thus effectively allowing the physicochemical properties (pH, temperature and contact duration), on the adsorption amount to be examined. Upon completion, the results indicated that the initial pH as well as the contact duration had notable effect on the adsorption amount. Conversely, the temperature change had an insignificant effect on the equilibrium adsorption amount. In addition, a dosage of 0.1 g of MaA, concentration of 1000 mg/L, pH ranging from 6 to 8, and temperature of about 25 °C were found to be the optimum process conditions for the adsorption of the examined heavy metals, whereas difference in contact time was recorded as follows: 1 h for Pb2+ and Cu2+ ions with adsorption amounts of 75.081 mg/g and 74.054 mg/g, respectively; and 3 h for Cd2+ ion with adsorption equal to 75.530 mg/g. In the analysis of the trend, the coefficients of correlation (R2 = 0.99) of the Langmuir isotherm model were increasingly consistent compared to Freundlich isotherm model (R2 from 0.10 to 0.55), thus indicating that the process to be a homogeneous monomolecular layer adsorption. Moreover, the kinetic aspects were similarly consistent in relation to quasi-secondary kinetic equation, which then further established that the process was primarily controlled by ion exchange, extra-particle, intra-particle, and liquid film diffusion. In addition, research on the potential reusability of MaA adsorbent after being employed to treat heavy metals was also performed. The crystalline phase of the composite after subjected to high temperature indicated wollastonite (CaSiO₃) and gregoryite (Na₂CO₃) as the main mineralogical phases. These minerals are beneficial in the preparation of functional building materials by promoting a sustainable solution for the full recycling of waste glass and contributing to efficient solid waste management and environment protection.

Waste tea as absorbent for removal of heavy metal present in contaminated water

The goal of this study is to investigate the efficacy of tea-derived absorbents for the removal of heavy metals from contaminated water. For this, absorbents were prepared from milk tea (MT) waste, Ilam tea (IT) waste, and various types of tea leaves, including Immature (IML), mature (ML), and old leaves (OL). The characterization of the absorbents revealed distinct physical and chemical properties from X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), with varying degrees of effectiveness observed across different absorbent types. Heavy metal removal efficiency was assessed using a chemical-free UV-spectrophotometer. The results show that the maximum removal efficiency for Cd using the IT absorbent reaches up to 82.14 % with 100 ppm cetyltrim ethylammonium bromide (CTAB), while the minimum removal efficiency is 32.14 % using the OL absorbent with 20 ppm CTAB. For Zn, the OL absorbent demonstrates a maximum removal efficiency of 52.59 % with 100 ppm CTAB, whereas the minimum efficiency is 3.70 % using the ML absorbent with 20 ppm CTAB. For Ni, the highest removal efficiency is achieved with the ML absorbent, reaching up to 97.73 % with 100 ppm CTAB, and the lowest is 31.82 % with the MT absorbent with 20 ppm CTAB. The addition of a catalyst further enhanced removal efficiencies in both absorbents and metals. Also, the removal of heavy metal ions using 0.05 g of tea absorbent combined with CTAB at varying concentrations. Results show that the addition of 20 ppm and 100 ppm CTAB significantly reduces metal ion concentrations from an initial 100 mg/L. The metal ion concentration decreases as CTAB concentration increases, demonstrating the effectiveness of CTAB in enhancing the absorption capacity of tea absorbent for heavy metal removal. The investigation of selective adsorption of Ni, Zn, and Cd by an adsorbent, revealing competitive adsorption behavior with Ni and Zn being adsorbed more rapidly than Cd, suggesting the impact of metal ion interference on adsorption efficiency. However, limitations were observed with certain absorbent types; for instance, immature leaves did not effectively remove Ni. Overall, this study underscores the potential of tea-derived absorbents as sustainable solutions for mitigating heavy metal pollution in industrial wastewater. Further research is needed to optimize absorbent formulations and explore their applicability in real-world environmental remediation scenarios.

Engineered Bacteria Achieve Breakthrough 91% Lead Removal in Bioremediation

Background: Heavy metal pollutants pose a significant environmental and public health threat, necessitating effective remediation strategies. Genetically modified microorganisms, Shewanella oneidensis MR-1 and Cupriavidus metallidurans CH34, show promise in mitigating contamination. Specific Background: Engineered bacteria have been designed to improve metal absorption, specifically lead, mercury, cadmium, and zinc, but further research is needed to understand their effectiveness in different pH levels and water conditions. Knowledge Gap: Few studies have investigated the pH-dependent efficiency of genetically engineered microbes in heavy metal absorption or their performance under wastewater conditions, despite numerous studies on microbial bioremediation. Aims: The study evaluates the efficacy of genetically modified Shewanella oneidensis and Cupriavidus metallidurans in removing heavy metals from contaminated water at various pH levels. Results: The study found that both bacterial strains effectively removed 91% of lead at pH 7, with optimal levels for lead and cadmium absorption depending on the specific pH. Novelty: CRISPR/Cas9 technology is used for genetic modification of strains, enhancing microbial engineering for environmental remediation. Study provides new data on pH-specific absorption rates.. Implications: These findings can be applied to enhance the design of bioreactors and biofiltration systems, offering a sustainable solution to heavy metal contamination in wastewater, with broad potential for industrial and environmental applications. Highlights: Modified bacteria remove 91% of lead at neutral pH. CRISPR/Cas9 enhances bacteria for efficient heavy metal removal. pH optimization is key for effective heavy metal absorption. Keywords: Heavy metals, Bioremediation, Genetically modified bacteria, Shewanella oneidensis, Cupriavidus metallidurans

Bhargavaea beijingensis a promising tool for bio-cementation, soil improvement, and mercury removal

Microbially Induced Calcite Precipitation (MICP) has emerged as a promising technique for bio-cementation, soil improvement, and heavy metal remediation. This study explores the potential of Bhargavaea beijingensis, a urease-producing bacterium, for these applications. Six ureolytic bacteria were isolated from calcareous bricks mine soil and screened for urease and calcite production. B. beijingensis exhibited the highest urease activity and calcite precipitation. Urease activity, calcite precipitation, sand solidification, heavy metal removal efficiency, and compressive strength were evaluated. It showed significant heavy metal removal efficiency, particularly highest for HgCl2. Mortar blocks treated with B. beijingensis or its crude enzyme exhibited improved compressive strength, suggesting its potential for bio-cementation. Crack remediation tests demonstrated successful crack healing in mortar blocks using the bacterium or its enzyme. This study identifies B. beijingensis as a novel and promising MICP agent with potential applications in bio-cementation, soil improvement, and heavy metal remediation. Hence, B. beijingensis diversified abilities prove superior performance compared to commonly used strains like Bacillus subtilis and Shewanella putrefaciens in bio-cementation applications. Its high urease activity, calcite precipitation, and heavy metal removal abilities make it a valuable candidate for sustainable and eco-friendly solutions in various fields.

Interpretable machine learning for predicting heavy metal removal efficiency in electrokinetic soil remediation

Electrokinetic remediation (EKR) presents a promising approach for polluted soil remediation, leveraging electric fields to mobilize contaminants and facilitate their removal. Accurate efficiency prediction is crucial for optimizing EKR processes, reducing costs, and minimizing environmental impact. However, the EKR efficiency is influenced by numerous complex factors, making it challenging to predict outcomes reliably. This study introduces a novel approach for developing interpretable machine learning (ML) models tailored for efficient and unbiased EKR efficiency prediction based on material properties and experimental conditions. A large experimental dataset comprising 185 tests was compiled, encompassing various EKR parameters, heavy metal concentration, soil characteristics. A structured ML workflow was devised, evaluating diverse ML algorithms and employing model-agnostic interpretation methodologies to uncover intrinsic correlations between removal efficiency and pertinent attributes. Among the investigated ML models, Extreme Gradient Boosting (XGB) exhibited the best performance. Bayesian optimization was applied to further enhance its capabilities. The optimized XGB model demonstrated superior predictive accuracy on the test set, with an RMSE of 0.255, an MAE of 0.158, and an R² of 0.82. Moreover, SHapley Additive exPlanations analysis was employed to interpret the contributions of the input variables. Among inputs, electrode distance emerged as the most significant factor influencing EKR efficiency, followed by area, electrolyte species, and remediation duration. This research not only advances the predictive capabilities for EKR efficiency but also provides crucial insights into the underlying factors influencing remediation success, paving the way for more efficient and scalable applications in environmental management.

Biosorption of heavy metal ions using a wood-rot fungus Schizophyllum commune

In this study, the ability of live mycelia of Schizophyllum commune to remove heavy metals from aqueous solution was investigated. The influence of various experimental parameters, such as pH, temperature, and contact time on the biosorption process was investigated. The maximum biosorption capacity using live biomass was found as 81.5, 90.71, 70.18, and 66.18 mg/g for Pb(II), Sr(II), Zn(II), and Cd(II), respectively, at optimized conditions. The biosorption process reaches equilibrium between 180 and 240 min for the tested metal ions. The experimental data were used to study biosorption isotherm and kinetics models. The thermodynamic parameters, ΔG°, ΔH°, and ΔS°, showed that the biosorption process was endothermic and spontaneous at 303–343 K. SEM images revealed that the presence of metal ions altered the morphology of fungal hyphae. The presence of Pb(II), Sr(II), Zn(II), and Cd(II)on the fungal mycelia was confirmed using SEM-EDX. FTIR spectroscopy of biomass showed the involvement of functional groups like, -CH, amino acid, fatty acid, carboxyl group, and alkane and alkyl groups in adsorption of heavy metal ions. The adsorption capacity of S. commune for removal of heavy metals under the optimized conditions was Sr(II) > Pb(II) > Zn(II) > Cd(II). Thus, the study demonstrated an application of Schizophyllum commune for efficient removal of heavy metals from metal-contaminated water or industrial effluents.

Green synthesis of nano silver-modified date syrup 3D graphene for adsorptive removal of heavy metals from wastewater and its antibacterial efficiency

Abstract Many researchers are focusing on the eco-friendly and cost-effective green synthesis of materials for removing heavy metals from wastewater using materials made from natural sources. In this research, date syrup was used as a rich carbon source while potassium chloride particles were used as a substrate. Green synthesized silver nanoparticles modified the graphene foam to enhance its heavy metal removal and antibacterial efficiency. The morphology and structure of the graphene foam were examined using scanning electron microscopy and Raman spectroscopy. The Brunauer-Emmett-Teller method examines textural features such as surface area, pore volume and diameter. The study focused on evaluating the efficiency of removing heavy metals including cadmium, lead, zinc, and chromium from water. The results indicated that the date syrup graphene foam has high heavy metal removal efficiency despite the short contact time, especially for Cd2+ and Pb2+, with removal efficiencies of 68% and 39%, respectively. It shows a relatively lower efficacy for Zn2+ and Cr2+, with removal efficiencies of 10% and 27%, respectively. The addition of silver nanoparticles greatly improved the removal efficiency of Cd2+ (75%), Zn+2 (22%), and Cr2+ (33%). Moreover, the antibacterial efficacy test showed significant improvement after the nanosilver modification to reach a 100% bacterial-killing rate.