Adsorption Of Heavy Metals Research Articles

ENVIRONMENTAL ASPECTS OF WASTE-DERIVED BOTTOM BLEND CLAY LINERS INCORPORATING ZEOLITE AND BENTONITE

This research investigated the effects of incorporating bentonite and zeolite into bottom blended clay liners (BBCLs) on their engineering properties and adsorption capacity. BBCLs composed of clay, water treatment residue, and calcium carbide in a 40:40:20 ratio by volume were investigated with the addition of 1, 2, and 3 wt.% bentonite or zeolite. The experimental results indicated that bentonite and zeolite had positive effects on the slake durability index and the equilibrium time for the adsorption of lead (Pb) and chromium (Cr) from the leachate, whereas the unconfined compressive strength (UCS) and coefficient of permeability were negatively affected compared to those of the samples without bentonite and zeolite. At 56 days, the UCS of BBCLs with bentonite and zeolite decreased from 3.4 to 2.2MPa, while the coefficient of permeability of all the samples met the regulatory limit of sanitary landfills, which was given at 1×10-7cm/s. The slake durability index of all samples was lower 50% but it remained higher compared to BBCLs without bentonite and zeolite (approximately doubled). Both additives enhanced the equilibrium time and percentage of Pb and Cr adsorption by about 20% and 200%, respectively. SEM-EDS results show the adsorption of Pb and Cr onto the raw materials, calcium silicate hydrate (CSH), zeolite, and bentonite. Therefore, the addition of zeolite can increase the ability to adsorb heavy metals form leachate, which is suitable for use in secured landfills.

Effect of modifications on structure, physicochemical properties and lead ions adsorption behavior of dietary fiber of Flammulina velutipes

The health effects of dietary fiber have been widely concerned, which are closely related to physicochemical properties. This study focused on soluble dietary fiber of Flammulina velutipes (FDF), evaluated the effects of modifications on structural characterization, the physicochemical properties and the heavy metal adsorption characteristics, and further clarified underlying mechanisms on Pb2+ adsorption behavior of FDFs. The results showed the modifications of extrusion and cellulase improved the yield of FDFs, increased the release of active groups and enhanced the adsorption ability in vitro. Besides, Pb2+ adsorption altered porous structure and led to the presence of carboxylate. It was a spontaneous endothermic reaction and can be fitted by the pseudo-second-order kinetic equation. The Freundlich equation was suitable to describe the adsorption isotherm. These results highlighted potential applications of the dietary fiber modification and laid the theoretical foundation for the modification processing of F. velutipes and protection from food-derived heavy metal toxicity.

Removal of Pb(II) and Cd(II) from a Monometallic Contaminated Solution by Modified Biochar-Immobilized Bacterial Microspheres.

Lead (Pb) and cadmium (Cd) are toxic pollutants that are prevalent in wastewater and pose a serious threat to the natural environment. In this study, a new immobilized bacterial microsphere (CYB-SA) was prepared from corn stalk biochar and Klebsiella grimontii by sodium alginate encapsulation and vacuum freeze-drying technology. The removal effect of CYB-SA on Pb(II) and Cd(II) in a monometallic contaminated solution was studied. The results showed that the removal of Pb(II) and Cd(II) by CYB-SA was 99.14% and 83.35% at a dosage of 2.0 g/L and pH = 7, respectively, which was 10.77% and 18.58% higher than that of biochar alone. According to the Langmuir isotherm model, the maximum adsorption capacities of Pb(II) and Cd(II) by CYB-SA at 40 °C were 278.69 mg/g and 71.75 mg/g, respectively. A combination of the kinetic model, the isothermal adsorption model, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main adsorption mechanisms of CYB-SA encompass functional group complexation, ion exchange, electrostatic attraction and physical adsorption. The findings of this study offer practical and theoretical insights into the development of highly efficient adsorbents for heavy metals.

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II).

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

Investigating the Effect of UV Irradiation and TiO2 Addition on Heavy Metal Adsorption by Inverse Vulcanized Sulfur Polymers.

Organomercury contamination in wastewater is a longstanding global concern, prompting the establishment of the Mi-namata Convention in 2013, following the tragic Minamata Bay incident in Japan. Despite numerous proposed solutions, the development of an affordable and convenient adsorbent remains a challenge. Sulfur, being one of the most abundant elements globally, has shown promise in mercury adsorption in previous research. This study delves into the influence of light exposure on the process of mercury adsorption. Our findings reveal that exposure to UV-A wavelengths (315 nm - 400 nm), in combination with the addition of titanium dioxide (TiO2), enhances the adsorption capacity of a sulfur-rich polymer. The maximum observed adsorption capacity reached 47 mg/g under these conditions. Notably, the presence of TiO2 and UV exposure did not significantly impact the adsorption of inorganic mercury and gold.

Hydrochar from sawdust and sewage sludge – a potential media for retaining heavy metals in sustainable drainage systems (SuDS)

ABSTRACT Waste valorization is an essential aspect of sustainable development. From this perspective, co-hydrothermal carbonization (Co-HTC) is a promising thermochemical process for converting organic waste into hydrochar. Hydrochar is a solid material whose physicochemical properties could make it suitable for adsorbing pollutants such as heavy metals. Accordingly, this work evaluated the hydrochar from Co-HTC of sawdust and non-dewatered sewage sludge as a potential adsorbent of heavy metals at low concentrations. In the context of sustainable drainage systems (SuDS), it is notable that heavy metals are present at very low but still potentially harmful concentrations, which presents a potential opportunity for the application of hydrochar. Thus, three hydrochars (H-180, H-215, and H-250), produced by Co-HTC at 180, 215, and 250 °C, were tested herein for their ability to retain lead (Pb2+). The H-180 presented better performance than other hydrochars (H-215 and H-250), suggesting that chemisorption could be the main adsorption mechanism. Interestingly, the presence of other cationic heavy metals (Cu2+, Zn2+, Cd2+, Cr6+, and Ni2+) did not hinder the Pb2+ adsorption, for which the removal efficiency remained close to 100%. In fact, in such a multi-metal system, hydrochar can be suitable for capturing both lead and cadmium. Therefore, the hydrochar from Co-HTC of sawdust and non-dewatered sewage sludge can be useful for removing heavy metals at low concentrations, such as those found in urban runoff waters. Although further studies are required, these findings suggest hydrochar as a potential material for application in SuDS.

Remediation of Pb and Cd contaminated sediments by wheat straw biochar and microbial community analysis

Wheat straw biochar (BC) or modified wheat straw biochar (MBC) could affect the aggregate structure of soil, effectively adsorb heavy metal and reduce the bioavailability of heavy metals in soil. TGA, BET, FTIR and SEM were used to characterize the surface morphology and structure of BC and MBC. The adsorption properties of BC and MBC on Pb(‌II) and Cd(‌II) in solution systems were investigated by batch experiments, and the remediation performance of Pb and Cd contaminated sediment by BC or MBC were studied by pot experiments. The results showed that MBC had a larger specific surface area of 46.04 m2/g and total pore volume 0.0555 cm3/g; the adsorption isotherms of Pb(II) and Cd(II) for BC and MBC were more suitable for Langmuir model (R2 over 0.91), and the maximum adsorption capacities of Pb(II) and Cd(II) by MBC could reach 71.14 and 115.64 mg/g, respectively. BC or MBC promoted the transformation of Pb and Cd from the extractable acid fraction to the oxidizable and residual fraction, reduced the migration of heavy metals and enhanced the stability of aggregates. Therefore, the results provided a perspective for the dredged contaminated sediments used as planting soil. In addition, BC or MBC, as soil amendments, could improve the abundance of microbial community. At the phylum level, the main dominant bacteria were Proteobacteria and Bacteroidetes.

Active sites regulation and adsorption performance of Al-pillared bentonite for the removal of lead from aqueous phase

Developing an environmentally friendly adsorbent with high adsorption capacity and economic benefits is crucial for the treatment of lead-contaminated wastewater. In this study, active clay (A-bent) and Al pillared acid-activated clay (A-AlPILC) were prepared using natural bentonite as the carrier via acidification and pillar-supported technology. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption experiments, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence spectrometer (XRF). The results showed that the amended clay exhibited an increase in specific surface area (SSA) from 39.37 m2/g to 175.28 m2/g and 245.42 m2/g compared to raw bentonite. The interlayer spacing and total pore volume rose respectively. The adsorption technique achieved an impressive removal rate of 90.6 % for Pb(II). Adsorption data were fitted by adsorption kinetics and adsorption isotherm model. Based on the response surface method (RSM), and analysis of variance (ANOVA) showed that the influence of these variables was significant. The simulation of lead ions showed that the acidic functional groups and ligands promote adsorption more than they inhibit it. Using the density function theory (DFT) calculation, the bentonite cycle model was established to demonstrate the interaction between bentonite and lead, with a binding energy of −0.369 eV. Similarly, the density and energy band structure of the state were computed to explore the mechanism of heavy metal adsorption by clay minerals.

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.

Enhancing heavy metals removal from water by thiol-incorporation of UiO-66 based metal organic framework nanosheets with l-cysteine

A new adsorbent, Cys-2D-UiO-66, was developed and applied to effectively eliminate heavy metal ions from water. The synthesis of 2D-UiO-66 involved developing a two-dimensional structure of UiO-66, created through an alkaline reaction medium, deviating from the normal three-dimensional structure. The advantage of 2D-UiO-66 nanosheet with a high aspect surface-to-thickness ratio is its ability to easily expose active sites on their surface to contaminants in solution, without diffusion limitations. Further attempts were made to enhance the adsorption capacity of the 2D-UiO-66 adsorbent by attaching l-cysteine to its surfaces through a simple one-pot process. This resulted in the modified adsorbent, Cys-2D-UiO-66, which exhibited exceptional adsorption performance. The adsorption experiments revealed that using Cys-2D-UiO-66 significantly improved the adsorption of Hg2+, Pb2+, and Cd2+ compared to 3D-UiO-66 (i.e. a 52 % increase for Hg2+, a 9.5-fold increase for Pb2+, and a 20-fold increase in Cd2+ adsorption). The adsorption equilibria of Cys-2D-UiO-66 align more closely with the Langmuir model, indicating that monolayer chemisorption mainly dominates the adsorption behavior. The thermodynamic study demonstrated that the adsorption of heavy metals onto the Cys-2D-UiO-66 favors higher temperatures. This fact is supported by thermodynamic calculations showing exothermic, favorable, and spontaneous chemisorption. The Cys-2D-UiO-66 adsorbent exhibited exceptional reusability with a marginal (less than 4 %) drop in adsorption performance after five successive cycles. Multicomponent adsorption results indicated a decline in the amount of adsorption for all species compared to the single component state due to competitive adsorption. FTIR analysis indicated that S–H and N–H groups aid in heavy metal ion adsorption, with Hg2+ ions being more easily adsorbed than Pb2+ and Cd2+ ions due to their higher electronegativity and ability to form covalent bonds with sulfur.

Heavy metal adsorption on yellow loam clay modified by biomass- and biochar-decomposed liquids from Ficus microcarpa

In studing the heavy metal adsorption effect of decomposed liquid (Dl) on yellow loam clay (C), biomass-Dl (BmDl) and biochar-Dl (BcDl) from Ficus microcarpa leaves were used to modify C. The different Dl-modified Cs (Dl-Cs) were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. A batch method was used to study the adsorption kinetics and thermodynamics of Pb(II) and Cd(II), as well as the effects of decomposition time, modification ratio, pH, temperature, and ionic strength on the adsorption process. Results of microscopic morphology indicated that Dl was modified on the C surface, and it changed the surface properties. The adsorption isotherms of Pb(II) and Cd(II) by different Dl-Cs conformed to the Langmuir and Freundlich model, with the maximum adsorption capacity (qm) maintained at 65.64–163.89mmol/kg (BmDl-Cs) and 77.68–235.63mmol/kg (BcDl-Cs). Under the same conditions, the peak value of qm was reached at decomposition time of 14 days and 50% of Dl modification. pH = 6, ionic strength of 0.1mol/L, and 30 ℃ were the optimum conditions for the adsorption of Pb(II) and Cd(II) by different Dl-Cs. Pb(II) and Cd(II) adsorption was a spontaneous, endothermic, and entropy-increasing process, and pseudo-first-order kinetic equation was suitable to characterize adsorption.

Heterogeneous precipitation behavior and mechanism during the adsorption of cationic heavy metals by biochar: Roles of inorganic components

Heavy metals are commonly adsorbed by biochar in contaminated water and soil. However, the behaviour and underlying mechanisms of heterogeneous precipitation between the inorganic components of biochar and cationic heavy metals remain poorly understood. In this study, we comprehensively investigated the nucleation, growth, and aggregation of precipitates, ion exchange-coupled precipitation behaviour, adsorption-precipitation correlation, and the influence of environmental factors (e.g., anion content, pH, initial concentration, type of heavy metals, and biochar size). The kinetic results indicated that the generation of precipitates was accompanied by an adsorption reaction with a gradual increase in crystal size and aggregation behaviour. Moreover, precipitation includes both surface and solution precipitation. The increasing local concentration of Pb(II) around the biochar at high initial concentrations increased the supersaturation of the nucleating substance, which decreased the potential for heterogeneous nucleation and facilitated heterogeneous precipitation. Correlation analysis revealed the presence of a coupling mechanism between precipitation and cation exchange. The enhanced electrostatic attraction at high pH could lower the heterogeneous nucleation potential barrier, thus promoting heterogeneous precipitation. The small biochar size extended the induction time, which was unfavourable for heterogeneous nucleation. This study provides a deeper understanding of the heterogeneous precipitation behaviour of the inorganic components of biochar and cationic heavy metals.

Vortex-Assisted Magnetic Solid-Phase Extraction of Heavy Metals in Water and Food Samples Using Iron Oxide Nanoparticle-Impregnated Carboxymethyl-β-Cyclodextrin.

The excessive accumulation of heavy metals has adverse effects on the human body. Here, magnetic iron oxide-impregnated carboxymethyl-β-cyclodextrin was synthesized. The synthesized material was employed as a magnetic solid-phase extracting adsorbent for specific heavy metals like lead (Pb), nickel (Ni), copper (Cu), and cobalt (Co). Characterization was performed by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, and Fourier-transform infrared spectroscopy. The analytical merits, like detection limits (Pb: 1.38ng/mL, Ni: 0.5ng/mL, Co: 0.14ng/mL, and Cu: 0.55ng/mL) andquantification limits (Pb: 4.14ng/mL, Ni: 1.62ng/mL, Co: 1.85ng/mL, and Cu: 1.82ng/mL) were calculated. Similarly, the preconcentration and enhancement factors (15) and relative standard deviation (Pb: 3.5, Ni: 0.92, Co: 2.7, and Cu: 1.5) were also calculated. The interfering study shows that the method is highly selective. For validation, it was applied to certified reference materials such as the Institute of Nuclear Chemistry and Technology ornamental Basma tobacco leaves and trace metal double addition 63.4 environmental water with good percent recovery values (92%-99%). Real water and food samples were also used with satisfactory (90%-99%) recovery results.

Concurrent removal of Fe(II), Cu(II), and Zn(II) cations from acid mine drainage by an industrial solid waste - steel slag: Behaviors and mechanisms

Acid mine drainage (AMD) contamination poses a severe environmental threat and is a significant risk to human health. There is an urgent need to develop environmentally sustainable and technically viable solutions for water contamination caused by heavy metals. In this study, steel slag (SS) was used as a secondary resource to concurrently remove Fe(II), Cu(II), and Zn(II) from AMD. Because of the loose and porous structure, abundant functional groups, fast sedimentation velocity, and excellent solid-liquid separation, SS showed exceptional removal performance for heavy metal ions. The adsorption kinetic data of Fe(II), Cu(II), and Zn(II) showed good regression with the pseudo-second-order model. Besides, the adsorption of Fe(II) by SS conformed to the Freundlich model, whereas the adsorption of Cu(II) and Zn(II) followed the Langmuir model, with the maximum adsorption amounts of Cu(II) and Zn(II) being 170.69 and 155.98 mg/g. Furthermore, competitive adsorption was observed among Fe (II), Cu (II), and Zn (II) in a multi-component system, with the adsorption priority being Fe (II) > Cu (II) > Zn (II). The removal mechanism of Fe(II), Cu(II), and Zn(II) in AMD by SS mainly includes electrostatic attraction, chemical precipitation, and surface complexation. Interestingly, the leached concentrations of Fe(II), Cu(II), and Zn(II) from the spent slag after calcination were all within the detection limit of the Chinese emission standard, demonstrating excellent environmental stability. Theoretically, this renders it a viable candidate for use as an additive in construction materials. Meaningfully, the work offers a practical approach for energy-efficient and eco-friendly heavy metal ions adsorption, and the secondary utilization of SS also contributes to the sustainable development of the steel industry. It is beneficial to implement the development concepts of clean production and efficient utilization of industrial solid waste.

Cost-Effective Synthesis of MXene Cadmium Sulfide (CdS) for Heavy Metal Removal.

Background Environmental contamination resulting from the release of untreated industrial wastewater has emerged as a critical worldwide issue. These effluents frequently have high levels of heavy metals and antibiotics, which are bad for aquatic ecosystems and human health. Oftentimes, conventional wastewater treatment techniques fall short of effectively eliminating these pollutants. Innovative materials that may efficiently absorb or break down contaminants from contaminated water sources are, therefore, desperately needed. Hydrothermally produced MXene cadmium sulfide (CdS) composites have shown great promise as an adsorbent material because of their special qualities, which include high surface area, chemical stability, and customizable surface functions that improve their adsorption capacity for heavy metals and antibiotics alike. Aim The aim of this study is to produce MXene-CdS nanoparticles in a cost-effective method for the simultaneous removal of heavy metals from aqueous contaminants for water pollution control. Methods and materials MXenes were synthesized by selectively etching Ti3AlC2 MAX-phase ceramics using aqueous HF. CdS nanoparticles were synthesized separately and integrated with MXenes via a hydrothermal process. The resulting MXene CdS nanocomposites were characterized using scanning electron microscopy (SEM) for morphology, energy dispersion spectrum (EDS) for elemental composition, X-ray diffraction(XRD) study for phase identification, and removal of heavy metals viaMXene CdS. Results Consistent distribution of CdS nanoparticles on the MXene surface and the creation of MXene CdS nanomembranes with a well-defined shape were observed by SEM analysis. Ti, C, Cd, and S elements, indiciaries of a successful composite formation, were confirmed to be present by EDS. The crystalline structure of both the MXene and CdS phases was confirmed by the distinctive peaks seen in the XRD patterns. MXene-CdS composites facilitate the effective removal of chromium ions from contaminated water. The excellent hydrophilicity of the produced nanomembrane allowed for effective interaction with watery contaminants. Conclusion This study showcases the successful synthesis and characterization of MXene-CdS nanocomposites for environmental remediation, particularly in removing toxic metals like chromium from industrial effluents. SEM analysis confirmed the uniform distribution of CdS nanoparticles on the MXene surface, while elemental composition validated their integration. XRD analysis confirmed the crystalline structures of both components. The nanocomposite exhibited excellent hydrophilicity, enhancing the efficient adsorption of heavy metals. Its large surface area and chemical stability contribute to high adsorption efficiency, making it ideal for wastewater treatment. The scalable synthesis process supports practical applications. This research highlights MXene-CdS nanocomposites as a cost-effective, sustainable solution for water pollution control.

Polyacrylonitrile nanofibrous mat modified with cysteamine and ionic liquid as a recyclable and efficient adsorbent for selective removal of sulfonamides and Cu(II) from aqueous solution: Roles of multi-function adsorption

The combined contamination of heavy metals and antibiotics is a prevalent occurrence, yet the distinct chemical characteristics of these substances pose a significant obstacle to their simultaneous elimination. In this work, novel polyacrylonitrile nanofibrous mat (NFsM) modified with cysteamine and ionic liquid (IL@Cys@PAN NFsM) was developed using a cascade thiol-ene click reaction. The IL@Cys@PAN NFsM exhibits a rich array of functional groups and demonstrates strong binding affinity, fast mass transfer, and exceptional selectivity for sulfonamides (SAs) and Cu(II). The maximum adsorption capacities for SAs and Cu(II) in single-component systems were 122.3 and 97.4 mg/g respectively, according to the Langmuir isotherm model. The time dependent adsorption capacities followed a pseudo-second-order kinetic model, demonstrating a chemisorption-dominant process for each analyte. In binary pollutant systems, the co-occurrence of SAs and Cu(II) in water produced a competitive effect; however, the decrease in adsorption capacity was minimal. Through experimental analysis, FTIR characterization and density functional theory (DFT) studies, reasonable interactions of hydrogen-bond, electrostatic interactions, π-π stacking for SAs, and chelation effect for Cu(II) were proposed. Additionally, the reusability and recyclability of IL@Cys@PAN NFsM enhance its practicality for real-world applications. This paper presents the first systematic study on the simultaneous adsorption of heavy metals and antibiotics using NFsM, offering a novel perspective on the design of custom adsorbents capable of efficiently removing multiple contaminants with diverse characteristics while balancing eco-friendliness, excellent adsorption performance, and impressive recyclability for wastewater remediation.

Optimization of extracellular polysaccharides (EPS) production by Stenotrophomonas rhizophila JC1 and its protective effect on alfalfa under Pb2+ stress

Stenotrophomonas rhizophila JC1 and its extracellular polysaccharides (EPS) have been shown to effectively adsorb heavy metals in previous studies. The fermentation conditions of EPS by S. rhizophila JC1 were optimized using the Box-Behnken design (BBD). The composition, structural characteristics, and heavy metal adsorption capacity of EPS were systematically evaluated. The alleviation mechanism of Pb2+ stress on alfalfa was investigated through EPS inoculation. The maximum EPS yield reached 0.313 %. EPS consisted of glucose, glucosamine, galactose, and mannose in a molar ratio of 12.20:1:22.29:1.68. EPS also contained four distinct polymers with molecular weights of 623,683.71 Da, 144,072.27 Da, 105,892.21 Da, and 51,094.79 Da. The adsorption processes conformed to the pseudo-second-order model and Langmuir isotherm model. High Pb2+ concentrations significantly reduced germination percentage, germinative force, root length, fresh weight, and soluble protein, inhibited photosynthesis, exacerbated oxidative stress, and caused damage to the antioxidant system, thereby inhibiting seedling growth. EPS at low concentrations can promote alfalfa seed germination and mitigate Pb2+ stress by reducing the aforementioned damage. This study highlights the potential of EPS in soil remediation and enhancing plant resistance to heavy metal stress.

Valorization of carbon soot ash for the selective capture of lead ions from industrial waste water–A waste to resource approach

Landfills are struggling to accommodate the increasing amounts of carbon soot ash waste from oil refineries. Due to extensive industrial productions, large quantities of lead ions are released into the environment, which not only pollutes the environment but also affects flora and fauna. In this work, these urgent environmental issues will be tackled by studying the use of modified carbon soot ash for specific heavy metal adsorption. Carbon soot ash modified with chemical leaching and physical ball-milling was loaded onto the surface of graphene oxide. This adsorbent was found to selectively adsorb and remove toxic lead ions (>99%) from a mixed heavy metal solution. The adsorption efficiency was found to increase with temperature (20–60 °C) and pH (2–8). Langmuir isotherm and pseudo-second order kinetics were found to fit the adsorption process through curve fitting, where the adsorbent reached a maximum capacity of 194.55 mg/g. Potential mechanisms for lead adsorption and metal specificity are also discussed here. This work aligns with the waste-to-resource pathway, where waste carbon soot ash is diverted from landfilling and is formulated as a specific heavy metal adsorbent, that shows promise for environmental remediation.

Utilization of waste PET-derived metal–organic framework grafted polyaniline composite for heavy metal adsorption from aqueous solution

In this research, we used waste polyethylene terephthalate (PET) bottles as a source to develop an iron-based MOF-supported polyaniline (Fe-MOF@PANI) composite, which was then applied for the adsorptive removal of cadmium (Cd(II)) and lead (Pb(II)) ions from aqueous environment. A comprehensive characterization of the Fe-MOF@PANI composite was conducted using several analytical techniques including FTIR, PXRD, SEM, EDX with mapping, and XPS analysis, which provided significant insights into its functionality, crystalline structure, surface morphology, and elemental composition. The synthesized Fe-MOF exhibited a spindle-shaped morphology that was evenly distributed over the surface of the PANI composite, as confirmed by SEM analysis. Additionally, the porous characteristics of the Fe-MOF@PANI composite were proven through BET analysis. The Fe-MOF@PANI composite exhibited remarkable adsorption efficiencies for selected metal cations, achieving adsorption capacities of 143.36 mg/g and 258.59 mg/g for Cd(II) and Pb(II) ions, respectively. The findings of the isotherm and kinetic studies demonstrated that the adsorption process fitted well with Langmuir and pseudo-second-order kinetics, indicating that adsorption of both metal cations occurs in a monolayer formation and includes chemisorption mechanisms, respectively. This research paves the way for further development and application of post-functionalized PET-derived MOF adsorbents to remove Cd(II) and Pb(II) ions from water efficiently.

Preparation and performance study of sludge biomass bamboo charcoal

Abstract The purpose of this study is to explore a new low-cost and high-efficiency biochar adsorption material. The residual sludge as solid waste and fresh bamboo with fast growth and high yield were used as raw materials, modified by the KOH chemical activation method, and pyrolyzed in a tubular furnace with nitrogen atmosphere to obtain sludge biomass bamboo charcoal. In the performance test, the H2S gas adsorption experiment in a fixed bed reactor and the heavy metal adsorption experiment in soil were designed. Using different proportions of biochar, the preparation process of biochar was optimized by adjusting the raw material ratio and activation conditions. The results showed that when dealing with H2S gas, the appropriate amount of sludge can improve the adsorption effect, while the increase of bamboo component will reduce the adsorption rate. In the soil Cr(VI) restoration experiment, it was found that the best restoration effect was achieved after adding 10% biochar and applying it for 28 days, and the restoration rate reached 63.5%.