Heavy Metals In Wastewater Research Articles

Modeling and Optimization of Cadmium and Lead Adsorption onto Natural Pterocarpus santalinoides Fruit

The presence of heavy metals in wastewater has raised concern in developing countries because of their impact on human health and environmental ecology. Therefore, this study aims to remove cadmium and lead ions from wastewater using natural Pterocarpus santalinoides fruit through the adsorption method. The Box-Behnken design (BBD) of the response surface methodology (RSM) method was adopted to optimize the process variables such as contact time (20-100 min), adsorbent dose (0.1-0.5 g), initial metal ion concentration (10-50 mg/l), and temperature (30-70 °C). The ANOVA results clearly indicate that the linear model was not sufficient to best predict the removal performance of cadmium (R2 = 0.4009) and lead (R2 = 6353). The optimum conditions for the maximum Cd (94.81%) and Pb (89.23 %) adsorption onto the adsorbent were achieved at contact time (42.16 min), adsorbent dose (0.25 g), initial metal ion concentration (21.52 mg/l), and temperature (37.00 °C). According to the findings of the present work, Pterocarpus santalinoides shows to be a potential eco-friendly and cheap adsorbent for the removal of Cd and Pb from aqueous solutions. The BBD-RSM actual and predicted values of the Cd and Pb ions response show non-significant correlation, suggesting poor agreement between the two, revealing that the BBD-RSM model applied is not effective for the relationship between the four parameters examined in the Cd and Pb ions removal process.

Composite of Hydrolyzed PAN and β-Cyclodextrin Forms a Nanofiber Membrane with an Excellent Removal Effect on Various Cationic Dyes and Copper Ions.

The presence of dyes and heavy metals in wastewater represents a significant environmental and public health hazard, necessitating the development of efficient materials for their removal. In this study, we modified hydrolyzed polyacrylonitrile (PAN-H) and combined it with β-cyclodextrin (β-CD) by using an electrostatic spinning technique to fabricate composite nanofibrous membranes for water treatment applications. The resulting PAN-H/β-CD nanofiber membranes exhibit spindle-shaped fibers and porous structures with a high density of charged functional groups, which significantly enhance their selective adsorption capacity compared to pure PAN fibers. Furthermore, post-treatment with a sodium bicarbonate solution further improved this capacity, resulting in the membranes demonstrating a remarkable adsorption efficiency for cationic dyes. The adsorption process conformed to the Langmuir and pseudo-second-order kinetic models, with maximum adsorption capacities of 216.94 mg/g for methylene blue (MB), 471.59 mg/g for malachite green (MG), 299 mg/g for crystal violet (CV), and 43.95 mg/g for copper ions. The selective adsorption of these positively charged contaminants, particularly cationic dyes and metallic copper, indicates that PAN-H/β-CD membranes have significant potential for the treatment of wastewater containing similar pollutants.

Fabrication of tight polyamide nanofiltration membrane by using a pyridine-diamine precursor for heavy metal ions removal

Nanofiltration offers a promising solution for removing heavy metal ions from wastewater, thereby mitigating ecological and environmental risks. In this study, we synthesized a novel pyridine-diamine precursor 2,6-dipiperazine pyridine (PyBPIP), and employed it as the sole aqueous monomer to fabricate tight polyamide (PA) nanofiltration (NF) membranes via interfacial polymerization (IP) method with trimesoyl chloride for the separation of heavy metals. The resulting membrane features an ultrathin PA functional layer (approximately 60 nm), a lower molecular weight cut-off of 251 Da, and a weakly negatively charged surface. This NF membrane exhibits competitive water permeance of approximately 7.67 LMH/bar and excellent rejection rates exceeding 98 % for various heavy metals ions including Zn2+, Mn2+, Cu2+, along with outstanding separation performance for other divalent cations. Additionally, the NF membrane also exhibits robust stability during the 72-h operational test. In summary, this study demonstrates the feasibility of designing suitable monomers for the preparation of highly perm-selective NF membranes for the removal of heavy metal ions in wastewater.

Electrochemically Switchable Sulfurized Polyacrylonitrile for Controllable Recovery of Copper in Wastewater Based on Reversible Adsorption/Desorption Regulation.

Within the context of circular economy and industrial ecology, adsorption offers an effective manner for recycling resources from wastewater, but controllable desorption remains a challenge. Inspired by metal-thiol binding and reversible thiol-disulfide redox transformation in biological systems, this study reports the development of a reversible adsorption/desorption (RAD) system for controllable recovery of copper based on electrochemically switchable sulfurized polyacrylonitrile (SPAN). Density functional theory calculations offered theoretical prediction for the formation of S-Cu bonds and reversible weak interaction between S-S bonds and Cu2+. The SPAN anchored onto titanium suboxide ceramic foam (SPAN@TiSO) could regulate Cu2+ adsorption/desorption stimulated by the electrode potential, indicated by the adsorption capacity of 243.3 mg g-1 (30 min) at 0.2 V vs SHE and a desorption efficiency of 98.4% (5 min) at 0.8 V vs SHE. Electrochemical analysis revealed that the reversible redox transformation of S-S/-S- groups in SPAN was responsible for selective adsorption and rapid desorption in response to the electrode potential. This study provides a proof-of-concept demonstration of an electrochemically switchable polymer to build up a reversible RAD system for controllable recovery of heavy metals in wastewater, making value-added resource recovery more efficient, more intelligent, and more sustainable.

Self-catalytic enhancement of Cu-EDTA decomplexation and simultaneous Cu recovery via a dual-cathode electrochemical process

Heavy metals that are readily chelated with coexisting organic ligands in industrial wastewaters impose threats to environment and human health but are also valuable metal resources. Traditional treatment methods generally require additional chemicals and generate secondary contaminants. Here, a reagent-free dual-cathode electrochemical system was proposed for the efficient destruction of Cu-organic complexes and synchronous cathodic recovery of Cu, whereby in situ production of H2O2 at carbon aerogel (CA) cathode was coupled with the reduction of Cu(II) to Cu(I) and finally to Cu(0) at Ti cathode. The intermediate Cu(II) complexes enabled the self-reinforced degradation owing to their higher activities toward •OH generation by activating H2O2 in contrast to initial Cu-ethylenediaminetetraacetic acid (Cu-EDTA). The enhanced production of Cu(I) by Ti cathode facilitated both •OH and Cu(III) formation, and the copper redox cycle was realized in the self-reinforced system, maintaining its sustainable catalytic activity. The energy cost of the dual-cathode system is 0.011 kWh/g for decomplexation and 0.057 kWh/g for Cu recovery, which is much lower than single Ti or CA cathode system. This established process provides a prospective approach for cost-effective destruction of chelating metal complexes and metal resources recovery from heavy metal wastewaters.

Mechanistic insight of fungal–microalgal pellets in photobioreactor for heavy-metal wastewater bioremediation

The high cost of harvesting microalgae limits their industrial application. Fungal–microalgal pellets can efficiently harvest microalgae and enhance heavy-metal adsorption. However, the molecular response mechanism of fungal–microalgal pellets under heavy-metal stress remains unclear. Fungal–microalgal pellets in a photobioreactor were used as a research object, and a 98 % harvesting efficiency could be achieved with adding exogenous carbon and nitrogen at pH 5.0–6.0 for 12 h of co-culture. Humic acid- and tryptophan-rich proteins in extracellular polymeric substances (EPS) participate in Cd(II) complexation. The Cd(II) response in fungal-microalgal pellets involves amino acids, glucose, lipids, energy metabolism, and antioxidant systems. The turning point was at 48 h. Proline, histidine, and glutamine synthesis and the adenosine-triphosphate (ATP) binding cassette (ABC) transport pathway play important roles in resistance to Cd(II) biotoxicity. This study provides a reference for the large-scale cultivation of fungal-microalgal symbiotic pellets and the practical application for industrial heavy-metal wastewater.

Advanced solar-driven hydrogel sponge for efficient heavy metal wastewater purification and clean water production through interfacial evaporation

Solar-driven interfacial evaporation (SDIE) technology represents a promising solution for freshwater harvesting, characterized by its cost-effectiveness, eco-friendliness, and sustainability. Nevertheless, achieving efficient removal of heavy metal ions during the SDIE process remains a significant challenge. In this study, we present a cost-effective method to construct a hybrid hydrogel evaporator by incorporating the konjac glucomannan (KGM) and reduced graphene oxide (rGO) into a polyvinyl alcohol (PVA) network. The hybrid hydrogel evaporator features a three dimensional layered structure, full spectrum absorption capability, high stability and inherent salt diffusion ability. These characteristics enabling a evaporation rate of 1.61 kg m−2 h−1 from wastewater across varying pH values (2-12) and high salinity levels (1 kW m-2). Significantly, the hybrid polymer network within the hydrogel is rich in -OH groups, enabling concurrent wipe off heavy metal ions and organic dyes from wastewater. The results in a ten thousand times reduction in the concentration of heavy metals such as Cr3+, Mn2+, Cu2+, Zn2+, and Pb2+ in the wastewater. This study provides new insights into solar evaporation technology and contributes to addressing challenges related to water scarcity.

Sulfadimethylpyrimidine degradation by non-radical dominated peroxomonosulfate activated with geopolymer-loaded cobalt catalysts

Geopolymers are frequently employed as adsorbent materials to treat heavy metals in wastewater due to their special structure analogous to that of zeolites. Nevertheless, their utilization as catalyst supports has not been extensively employed. In this study, geopolymers were modified using carboxymethyl chitosan and subsequently converted into zeolite through the hydrothermal method. Following calcination with Co loading, Co@MGA was obtained. The results indicated that as-prepared Co@MGA exhibited an excellent performance in activating PMS to degrade SMT. Moreover, the mineralization rate of SMT reached 76 %. Quenching experiments and electron paramagnetic resonance analyses had demonstrated that the non-radical pathway predominated in the degradation process of SMT, and 1O2 was the primary reactive oxygen species. The formation of surface bond was further elucidated through in-situ Raman spectroscopy and electrochemical tests. The potential mechanism and pathways of SMT degradation within the Co@MGA/PMS system were proposed. The system exhibited adaptability to different pH levels and robust resistance to inorganic ions and humic acid. Co@MGA demonstrated excellent reusability and stability, suggesting that Co@MGA is a highly promising catalyst for the activation of PMS.

Controlling synthesis of defect state lignin-derived carbon and application for U(VI) removal from aqueous solution: Effects of oxygen-defect and grain-size

Lignin has deemed to be the main polluting component of paper industry wastewater. But developing a potential strategy for utilization of lignin is a challenges problem. Lignin derived materials present potential performance for heavy metal wastewater treatment due to their unique physicochemical properties, and were found to be promising candidate materials in U(VI) removal. However, it is still lacking of a comprehensive understanding that the influences of surface oxygen-defect and grain-size on U(VI) removal processes. Here, using lignin as the raw material, combining plasma treatment technology to prepare defect states Lignin Derived Carbon (LDC), and exploring the influences of surface oxygen-defect and grain-size on their removal U(VI) process. The results indicated that with the reducing of LDC particle size (from ∼4 to ∼ 1 μm), the removal performance of U(VI) was improved. And the U(VI) removal performance of LDC was further improved by introducing of oxygen defect via H2 plasma etch. The characterization analysis of defect states LDC before and after reaction with U(VI) shown that the U(VI) removal mechanism was dominated by defects site complexation. These finding provide deep insight into the recycling of industrial solid wastes lignin and improving of U(VI) removal performance via defect controlling technology.

A Facile Two-Step Utilization of Sorghum Waste Derived Activated Carbon

Sorghum (Sorghum bicolor (L.) Moench) is an agricultural commodity that produces waste, including stems, during its cultivation. Sorghum stems can be used as an alternative precursor for forming activated carbon (AC) with a high surface area by utilizing ZnCl2 as an activator and followed by a pyrolysis process at 750 °C under N2 gas. In this study, AC from sorghum stems was sequentially used as an adsorbent for heavy metals in wastewater, as well as applied as an anode material for lithium-ion batteries. From the characterization analysis, the synthesized AC has an amorphous structure, a high carbon content of > 90%, and a surface area of 1189 m2/g. AC was applied to adsorb 10, 50, and 100 ppm of metal cobalt (Co) at 30 °C. The adsorption isotherm and kinetics of metal Co showed an adsorption capacity of around 28.2 mg/g. The Langmuir isotherm model also describes Co adsorption and follows the pseudo-first-order equation. As for the Li-ion anode material, the ACs material is fabricated on a cylindrical battery with LiNi0.8Co0.1Mn0.1O2 as the counter cathode material. The specific discharge capacity results are 104 mAh/g at the voltage window of 2.7-4.3 V. The sequential utilization of sorghum stem-derived activated carbon can improve the product’s sustainability, and such an approach is promising to be applied in other biomass-based waste treatments.Keywords: Activated carbon, adsorption, battery, biomass, sorghum

Recovery of ammonia assimilating microbiome after Cr (VI) shock by bio-accelerators

The pretreatment process is often unable to completely intercept heavy metals in wastewater, facing a huge risk of leakage, increasing the difficulty of treating pollutants in the subsequent biochemical process or even leading to the collapse of the system, and facing the difficulty of inoperability and rehabilitation. Heterotrophic ammonia assimilation has the potential to maintain some stability after heavy metal shock, thanks to its rapid microbial proliferation, robust resistance to high loads, remarkable environmental adaptability, and inherent stability. Bio-accelerators dosing strategies could strengthen the performance recovery ability of traditional bio-system after heavy metal impact. However, no recovery strategies for inhibiting HAA have been reported. Herein, three bio-accelerants, specifically, vitamin A, 6-benzylaminopurine, and α-ketoglutaric acid, were investigated for their potential to restore the HAA system impacted by 20 mg/L Cr (VI). The three bio-accelerants effectively mitigated the toxicity of the HAA system, resulting in a 60.4% increase in NH4+-N removal efficiency within just 6 days with cytokinin. During toxicity remediation, three bio-accelerants facilitated the production of extracellular protein components in soluble microbial products and stimulated the secretion of extracellular polymeric substances. The three bio-accelerants enhanced competition among genera and influenced community assembly processes to regulate community structure and enhance functional gene expression. This study offers a practical approach to enhancing the HAA process and remediating microbial toxicity.

Significant improvement in the removal performance of decimeter-sized zero-valent iron plates for mixed heavy metal ions in wastewater by enhancing surface sharpness

This study aims to lower the work function (Wa) of a decimeter-sized zero-valent iron plate (DZVIP) by introducing surface sharpness (TDZVIP) during stirring. Sharpness was achieved by cutting isosceles triangles with heights of 1 cm and varying apex angles (α) of 10˚, 20˚, 30˚, 40˚, and 50˚. A mixed simulated wastewater containing Cu(II), Te(IV), Se(IV), As(III), Bi(III), and Pb(II) at concentrations exceeding emission standards was prepared. Results indicate that the removal process exhibits mixed kinetic behavior, and sharpness significantly enhances the removal capacity (Re), mean removal rate (Vm), recycling performance, and final discharge quality. The Vm values for Cu(II), Te(IV), Se(IV), As(III), Bi(III), and Pb(II) over TDZVIP with optimized α are 2.34, 1.97, 1.51, 1.59, 4.09, and 1.53 times higher, respectively, than those over PDZVIP (without sharpness). UPS measurements provide direct evidence of Wa reduction, while XRD offers indirect confirmation. This is the first time the Wa of the amorphous shell has been identified and verified as a critical potential barrier for core electrons transferring from the DZVIP surface to wastewater. Additionally, it has been successfully reduced by incorporating surface sharpness and stirring, leading to enhanced removal efficiency, improved recycling performance, and higher final discharge quality.

A 3D aerogel evaporator for efficient solar interfacial evaporation: Breaking through the upper limit of steam production rate

Solar desalination is the most effective way to obtain clean and cheap fresh water. However, its lower upper limit of steam production rate limits its development and practical applications. In this paper, a microcrystalline cellulose aerogel composite Mo2C evaporator (MCAM) was prepared by combining Mo2C with microcrystalline cellulose aerogel (MCA). The evaporator consists of MCAM photothermal layer, polyurethane (PU) sponge insulation layer and one-dimensional water channel. Mo2C has high-light absorption efficiency. At the same time, the vertical channel inside the MCA makes the incident light be reflected and absorbed for many times inside. Benefiting from the synergistic effect of the vertical channel of MCA and the light absorption ability of Mo2C, MCAM obtained a high light absorption efficiency of 96.96 %. The interaction between the MCAM evaporator and water can reduce the evaporation enthalpy, thereby breaking the upper limit of the steam generation rate. Therefore, the evaporator achieved a steam production rate of 1.92 kg⋅m−2⋅h−1 and an energy utilization efficiency of 118.2 %. In addition, MCAM shows excellent salt tolerance and self-discharging salt ability, which ensures its stable operation in high-salinity environment. Besides its high efficiency, MCAM has significant purification effect on simulated seawater, heavy metal wastewater, and organic wastewater. This study provides a new strategy for further improving the steam production rate of the solar interface evaporator.

Controllable H2S supply via membrane contactors for safe and efficient arsenic precipitation from acidic wastewater

Sulfide precipitation is a popular technique for the treatment and resource recovery of arsenic-containing dirty acid wastewater. However, this approach frequently suffers from toxic hydrogen sulfide (H2S) escape and agent wastage issues. Herein, a safe and efficient technique is proposed based on a polytetrafluoroethylene membrane contactor wherein the mass transfer resistance of the gas, membrane, and liquid phases can be easily and independently regulated to control the H2S supply. Additionally, H2S is transferred in bubble-free form, fundamentally avoiding the issue of gas escape, and uniform membrane distribution contributes to evenly distributed H2S delivery. The results demonstrated that 99.3% arsenic precipitation could be achieved and the H2S emission ratio was limited to <0.12%, which was significantly better than traditional methods. Thus, highly efficient separation and resource recovery of heavy metals in wastewater can be achieved using this unique and controllable low-dose H2S supply method. The separation factor between copper and arsenic was as high as 7490.9. This study provides a safe, reliable, and promising new approach for the treatment of arsenic-containing acidic wastewater.

Micellar-enhanced ultrafiltration of heavy metal wastewater with palygorskite under various temperatures and pressures

The micellar-enhanced ultrafiltration process demonstrated significant potential for treating heavy-metal-contaminated wastewater. Operating conditions greatly influence complex formation and ultrafiltration efficiency, suggesting that optimizing these parameters could enhance both the process's effectiveness and its cost-efficiency. In this research, nano-palygorskite was used to treat wastewater contaminated with Cu2+, Zn2+, and Cd2+. The material was characterized using SEM, FTIR, XRD, and Zeta potential, and the effects of temperature and pressure variations on the process were investigated. Under conditions of pH 7.0 and 0.1 MPa, the retention rates of the three heavy metal ions rapidly equilibrated within 40 min, achieving removal efficiencies of 99.94 %, 99.75 %, and 99.56 %, respectively. Temperature changes significantly influenced the retention rates, which increased by approximately 5 % with increasing temperature. At pH 7.0 and 293 K, increasing the pressure improved the retention rates by approximately 3 %, reaching 99.31 %, 98.63 %, and 99.19 %, respectively. The experimental data fit the pseudo-2nd-order kinetic equation and Langmuir isotherm adsorption model, with maximum adsorption capacities of 10.44 mg/g, 9.41 mg/g, and 11.36 mg/g, respectively. Overall, gradual increases in the temperature and pressure accelerated the reaction rate, highlighting their beneficial effects on MEUF. This study underscores the potential of palygorskite as an effective inorganic complexing agent for heavy-metal-contaminated wastewater treatment.

Enhanced absorption capacity and fundamental mechanism of electrospun MIL-101(Cr)-NH2/PAN nanofibrous membranes for Mo(VI) removal

Amidst the escalating global concern over heavy metal discharge from industrial effluents, Mo(VI), as a potentially toxic trace element, poses significant risks to human and environmental health. Traditional treatment methods such as biodegradation and ion exchange have low removal efficiency, hence, the efficient removal of Mo (VI) ions from industrial wastewater assumes paramount importance. Emerging materials, Metal-Organic Frameworks (MOFs), have garnered extensive attention in water treatment due to their strong adsorption properties, and MOFs membrane materials are hailed as the most promising adsorbents. Therefore, this study aims to prepare a novel membrane material with high efficiency for the removal of Mo (VI) by loading MOFs into nanofibers. Given the water stability of MIL-101, MIL-101-R(-H, -NH2, -NO2) with different functional groups were prepared and subsequently loaded into PAN nanofibrous for the adsorption of Mo(VI). Adsorption kinetics and isotherm studies revealed PAN/MIL-101(Cr)-NH2 to exhibit superior adsorption performance, achieving a maximum adsorption capacity of 171.81 mg g-1. Density functional theory (DFT) calculations and molecular dynamics simulations elucidated the adsorption mechanism, highlighting the role of amino modification in facilitating Mo(VI) adsorption through electrostatic attraction and high reactivity. This work not only offers novel materials and approaches for Mo(VI) wastewater treatment but also advances the industrial application of MOF materials in the domain of heavy metal wastewater treatment.

Prediction of Biochar Adsorption of Uranium in Wastewater and Inversion of Key Influencing Parameters Based on Ensemble Learning.

With the rapid development of industrialization, the problem of heavy metal wastewater treatment has become increasingly serious, posing a serious threat to the environment and human health. Biochar shows great potential for application in the field of wastewater treatment; however, biochars prepared from different biomass sources and experimental conditions have different physicochemical properties, resulting in differences in their adsorption capacity for uranium, which limits their wide application in wastewater treatment. Therefore, there is an urgent need to deeply explore and optimize the key parameter settings of biochar to significantly improve its adsorption capacity. This paper combines the nonlinear mapping capability of SCN and the ensemble learning advantage of the Adaboost algorithm based on existing experimental data on wastewater treatment. The accuracy of the model is evaluated by metrics such as coefficient of determination (R2) and error rate. It was found that the Adaboost-SCN model showed significant advantages in terms of prediction accuracy, precision, model stability and generalization ability compared to the SCN model alone. In order to further improve the performance of the model, this paper combined Adaboost-SCN with maximum information coefficient (MIC), random forest (RF) and energy valley optimizer (EVO) feature selection methods to construct three models, namely, MIC-Adaboost-SCN, RF-Adaboost-SCN and EVO-Adaboost-SCN. The results show that the prediction model with added feature selection is significantly better than the Adaboost-SCN model without feature selection in each evaluation index, and EVO has the most significant effect on feature selection. Finally, the correlation between biochar adsorption properties and production parameters was discussed through the inversion study of key parameters, and optimal parameter intervals were proposed to improve the adsorption properties. Providing strong support for the wide application of biochar in the field of wastewater treatment helps to solve the urgent environmental problem of heavy metal wastewater treatment.

Fabrication of a polyoxometalate-based metal-organic compound and its derivative for enhanced photocatalytic, electrocatalytic, and electrochemical sensing properties

A novel polyoxometalate-based metal-organic compound (POMOC), namely [Ag(3-pna)2(H2PW12O40)]n (compound 1, where 3-pna = N-(pyridine-3-yl)nicotinamide), had been successfully synthesized and structurally characterized. The photocatalytic performance of compound 1 for the degradation of gentian violet (GV) and methylene blue (MB) was investigated in detail, which exhibited good cyclic stability as a photocatalyst. In addition, cyclic voltammetry technology was used to verify that compound 1 exhibited excellent electrocatalytic performance towards KBrO3 and H2O2. To improve the degradation of organic dyes and electrochemical sensing performance, a negatively charged oxygen vacancy metal oxide compound 1@C was prepared via pyrolysis using compound 1 as a precursor. Compound 1@C was investigated as an adsorbent, and was found to effectively remove MB and GV from wastewater, with adsorption rates of 824.36 mg/g and 957.02 mg/g, respectively. The performance of compound 1@C/glassy carbon electrode as an electrochemical sensor was studied using differential pulse dissolution voltammetry (DPV). This method proved effective in detecting heavy metal ions Cd2+ and Pb2+ in wastewater with the limits of detection as 4.65 and 1.69 μg/L, respectively. Compound 1@C/GCE showed good anti-interference capabilities and stability in detecting heavy metal ions in wastewater.

Boron/Fe2+/H2O2 combined with resins process cost-effectively remove Ni(II) in wastewater containing Ni-EDTA: Performance and mechanism

This study proposes a green purification strategy in which mild decomplexation of Ni-EDTA into other Ni complexes facilitates the efficient removal and recovery of nickel through resin adsorption. Decomplexation of Ni-EDTA by boron/Fe2+/H2O2 (B/Fe2+/H2O2) followed by resins adsorption was conducted for Ni(II) removal in Ni-EDTA. The Ni(II) removal efficiency could only achieve 1.3 % and 6.2 % while Ni(II) coexisted with EDTA but more than 10 times of higher when Ni(II) coexisted with EDTA-relatives via the single adsorption of commercial heavy metal-affined resins (D001 and D463), which attributed to the increased binding energies of these Ni-EDTA’s degradation products complexes than Ni-EDTA based on density functional theory (DFT) calculation. In comparing to precipitation, the resin adsorption required much less mineralization of EDTA to have a better removal efficiency of Ni(II). B improved the efficiency of Ni-EDTA decompexation by accelerating the recycle of Fe3+/Fe2+. The EDTA (and TOC) removal enhanced from 48.7 % (4.7 %) to 94.7 % (11.9 %) by B/Fe2+/H2O2 process comparing to Fe2+/H2O2 process. With the high EDTA but low TOC removal efficiency after B/Fe2+/H2O2 treatment, Ni(II) removal efficiency via resins adsorption could maximum achieve 80.5 %, 2–3 times of that via regular precipitation method. In addition, B and resins exhibited good reusability in five cycles, and B/Fe2+/H2O2-resins process had excellent adaptability to different heavy metal complexes. B/Fe2+/H2O2-D463 system not only could reduce 78.4 % reagents cost compared with that of Fe2+/H2O2-precipitation process, but also could save much cost than other processes. The results provide new insights for the cost-effective treatment of EDTA-complexed heavy metal wastewater.

Multi-ligand strategy for enhanced removal of heavy metal ions by thiol-functionalized defective Zr-MOFs

Given the significant global concern about heavy metal pollution, the development of effective adsorbents to capture pollutants has become an urgent issue. In this work, thiol-functionalized defective Zr-MSA-DMSA was designed by mixing 2,3-dimercaptosuccinic acid and mercaptosuccinic acid, which was applied for the rapid and efficient removal of M(II) (i.e., Pb(II), Hg(II), Cd(II)) from wastewater. Zr-MSA-DMSA exhibited excellent adsorption performance, and the maximum adsorption capacities for Pb(II), Hg(II), and Cd(II) were 715.2 mg g−1, 862.7 mg g−1, and 450.5 mg g−1. In actual wastewater, Zr-DMSA-MSA exhibited up to 97 % M(II) removal efficiency and excellent anti-interference ability. It also maintained good structural stability after five adsorption/regeneration cycles. Thus, the abundant oxygen vacancies and unsaturated adsorption sites on Zr-MSA-DMSA significantly improved the adsorption performance of M(II). Spectral analysis and DFT calculations confirmed that Zr-MSA-DMSA mainly relied on the coordination of sulfur and oxygen atoms, electrostatic attraction and a large number of defective sites to achieve the adsorption of M(II). Fixed bed experiments showed that Zr-MSA-DMSA exhibited a depletion time of 10500 min and a volume of 7.0 L. In summary, Zr-MSA-DMSA holds significant potential for treating heavy metal wastewater and provides potential applications for defect engineering.