Ni Removal Research Articles

Ligand imprinted composite adsorbent for effective Ni(II) ion monitoring and removal from contaminated water

Heavy metal especially nickel (Ni(II)) is the most pernicious kind of pollution since it is both poisonous and difficult to break down in nature and can cause many human disorders and diseases. The monitoring and removal of Ni(II) ions optically is required to enhance the quality of the water and make it appropriate for drinking as well as other uses around the residence. Therefore, the goal of the current work was to synthesize ligand imprinted composite adsorbent (MCA) and utilize it as an adsorbent to monitor and remove Ni(II) ions from the water. Based on the findings gathered, the MCA that was synthesized had a large particle size with a high surface area even after the ligand impregnation. The MCA was enhanced significantly in color with the contact of Ni(II) ion with limit detection at 0.35 µg/L. The maximum level of Ni(II) ions was eliminated (99 %) when the pH was adjusted to 5.50. The Langmuir model was also used to study the adsorption equilibrium data and the maximum adsorption capacity was 167.55 mg/g. Additionally, the method can selectively detect and remove Ni(II) even in the presence of diverse metal ions. Overall, the MCA offers an ideal platform for the on-site monitoring and removal of heavy metal ions, especially in resource-limited areas.

Preparation of chemically and thermally modified water caltrop epicarp (Trapa natans L.) adsorbent for enhanced adsorption of Ni(II) from aqueous solution

The present study aims to prepare waste water caltrop (Trapanatans L.) epicarp (WCS)-based adsorbents such as raw WCS (WCS-Raw), citric acid-grafted WCS (WCS-CA), acrylamide-grafted WCS (WCS-AM), and calcined WCS (WCS–Si) for Ni(II) removal from aqueous solution in batch adsorption process. The physical and chemical properties of the prepared adsorbents were investigated by different characterization techniques such as scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, nitrogen adsorption-desorption analyses, and pH at the Point of Zero Charge (pHpzc) in order to assess the suitability and effectiveness of the adsorbents for the removal of Ni(II) by understanding their surface morphology, chemical composition, porosity, and surface charge properties. The experimental Ni(II) adsorption data followed both the Langmuir isotherm and the pseudo-second-order kinetic model suggesting the adsorption process on the prepared adsorbents is well-described by these models. The modified adsorbents WCS-CA, WCS-AM, and WCS-Si exhibited a maximum adsorption capacity of 52.08, 40.32, and 158.73 mg/g, respectively, while WCS-Raw had a capacity of 29.06 mg/g. The thermodynamic study revealed that the adsorption process was feasible, spontaneous, and endothermic. The desorption study demonstrated that the adsorbents could be reused for multiple cycles with minimal loss of activity. The present work evidenced the potential practical applicability and sustainability of the WCS-based adsorbents as promising adsorbents in treating and removing Ni(II) from wastewater.

Compositional transformation of Ni2+ and Fe0 during the removal of Ni2+ by nanoscale zero-valent iron and the implications to groundwater remediation.

The use of nanoscale zero-valent iron (nZVI) to remove heavy metal ions like Ni2+ from groundwater has been extensively studied; however, the compositional transformation of the Ni2+ and Fe0 during the removal is not clearly comprehensible. This study provides an insight into the componential, structural, and morphological transformations of Ni2+ and Fe0 at a solid-liquid interface using various characterization devices. The underlying mechanism of transformation was investigated along with the toxicity/impact of the transformed products on the groundwater ecosystem. The results indicated that Fe0 is transformed into lath-like lepidocrocite (γ-FeOOH), twin-crystal goethite (α-FeOOH), and spherical magnetite (Fe3O4), while Ni2+ is converted into Fe0.7Ni0.3 alloy and Fe-Ni composite (trevorite - NiFe2O4) with a fold-fan morphology. The Fe0 transformation mechanism includes the redox of Fe0 with Ni2+, H2O, and dissolved oxygen, the combination of Fe2+ and OH- produced by Fe0 corrosion to amorphous ferrihydrite, and the further mineralogical transformation to Fe oxides with the aid of Fe2+ adsorbed on ferrihydrite. The conversion of Ni2+ is accomplished by reduction by Fe0 and surface coordination with Fe oxides. Compared with Ni2+ and Fe0, the toxicity and bioavailability of the transformed products are significantly reduced, hence conducive to the application of zero-valent iron technology in groundwater remediation.

Photocatalytic evaluation of synthesized MnO2/Fe3O4 NCs by Q. infectoria extract for removal Ni(II) and phenol: Study phytochemical, kinetics, thermodynamics, and antibioactivity

In the present study, the plant extract of the Quercus infectoria galls was used as a reducing, capping, and stabilizer agent for green synthesized MnO2 nanoparticles (NPs) and MnO2/Fe3O4 nanocomposites (NCs) due to its reduction ability from polyphenol and antioxidant content. The green synthesized nanomaterials have been characterized by various techniques such as FTIR, UV–vis, XRD, SEM, EDS, and TEM. The average size of about 7.4 and 6.88 nm was estimated for the NCs crystals of SEM images and XRD analysis by the Scherrer and Williamson-Hall methods. The green synthesized MnO2/Fe3O4 NCs (dosage: 0.1 g) have shown high photocatalytic activity for the removal of Ni(II) in acidic and basic solutions under visible irradiation (220 V lamp). The removal efficiency for the Ni(II) solution (3.6 × 10−3 M) at pH = 3 was increased to pH = 12 from 56 % to 98 %. The oxidase-like activity of MnO2/Fe3O4 NCs at different dosages (0.05, 0.1, and 0.15 g) for the removal and colorimetric of phenol (1 g/40 mL) in the presence 4-AAp (1 g) was seen after only 28, 13, and 5 s, respectively. The kinetic evaluation results showed the pseudo-second-order kinetics model closely matched the adsorption capacity theoretical values qe,cal (578.03, 854.70, 892.85, and 917.43 mg.g−1) and experimental values qe,exp (521.84, 839.74, 887.86, and 913.22 mg.g−1) at different initial pH solution (3−12) for Ni(II) removal. In addition, the investigation of isotherm models revealed that the Langmuir model (R2 = 0.9955) explains a better estimate for a monolayer and favorable removal of Ni(II) ions onto NCs. Also, the low Temkin constant, BT < 0 (0.0200 kJ.mol−1), and positive ∆H° value (0.103 kJ.mol−1.K−1) illustrated that Ni(II) removal is physical sorption and endothermic process. However, the obtained thermodynamic results showed the negative values ΔG° with the increase in temperature (303–318 K) toward a spontaneous removal process of Ni(II). Finally, the plant antioxidant (200 to 3200 μg/mL) and antimicrobial activities (0.001 to 0.1 g/mL) for plant extract, MnO2 NPs, and MnO2/Fe3O4 NCs were evaluated against Gram-positive and Gram-negative bacteria species.

The utilization of cost-effective natural sorbents for the eradication of heavy metal contaminants from the real world-based adsorbate system

In India, Industrial growth has resulted towards the release of numerous contaminated heavy metals into the environment, Various industries directly discharged the effluents containing harmful pollutants such as toxic heavy metals into the aqueous medium. There are numbers of treatment methods available to remove toxic elements from effluents before disposal. Several research investigations have been conducted to determine the capacity of unconventional absorbents to remove various wastewater impurities. Bio-sorption technique uses agricultural and natural left-over materials as adsorbents since they remain considerably less expensive, supportable, and available than traditional effluent treatment technologies. This study concentrates removal efficiency of orange peels (OP), rice husk (RH) and sugarcane bagasse (SCB) from the industrial effluents. Adsorption studies have been conducted for OP, RH and SCB with differing dose, pH, and contact duration, determined to be appropriate and leading to the highest levels of removal effectiveness. At 1.00 gm dosage, the maximum % removal efficiency of Cu, Cr, Ni, Cd and Zn removal for OP, RH and SCB were 84.90%, 90.45%, 86.21%, 98.00% and 74.11% respectively by using OP, RH and SCB the max. percentage removal efficiency of Cu, Cr, Ni, Cd and Zn for OP, RH were 82.81%, 76.80%, 76.16%, 78.46%, 78.59% at a pH value of 5, 6, 5, 7 and 7 respectively. The max. percentage removal efficiency of Cu, Cr, Ni, Cd and Zn using OP, RH and SCB were 93.45%, 93.05%,77.66%, 94.62%, 85.10% at the contact time of 120, 60, 120, 60 and 80 minutes respectively.

Со(ІІ) and Ni(II) Removal from Aqueous Solutions by Polymer and Polymer/Silica Adsorbents with Sulfo and Carboxyl groups

Sulfo and carboxyl group-containing polymers and polymer/silica adsorbents poly(acrylonitrile-co-2-acrylamido-2-methylpropane-1-sulfonic acid-co-acrylic acid-co-N,N’-methylene-bis-acrylamide) [poly(AN-co-AMPS-co-AAco-MBA)] and poly(AN-co-AMPS-co-AA-co-MBA)/SiO2 were synthesized by a UV-initiated polymerization or simultaneous UV-initiated polymerization and in situ sol-gel process and used as adsorbents for removal of Co(II) and Ni(II) ions from aqueous solutions. The adsorption capacity and the effect of the pH in the removal process have been studied. The poly(AN-co-AMPS-co-AA-co-MBA) adsorbent exhibited high efficiency: up to 91.8 % removal of Co(II) and 89.7 % removal of Ni(II). Polymer/silica adsorbents showed higher removal capacity as compared to pure polymer. The adsorption kinetics of Co(II) and Ni(II) ions were found to be satisfactorily described by the pseudo-second-order reaction equation of the Lagergren kinetic model, suggesting the ion-exchange nature of the process.

Inducing Rhizosphere Acidification in White Willow with Bacillus sp. ZV6 Enhances Ni Phytoextraction from Soil and Soil Quality

Chelating agents may decrease the extent of Ni phytoextraction by reducing plant growth and soil health due to Ni toxicity during enhanced phytoextraction. Contrarily, inducing acidity in the rhizosphere of Ni-accumulating plants with plant growth-promoting rhizobacteria (PGPR) having rhizosphere acidification ability can enhance Ni phytoextraction by increasing Ni bioavailability in the soil, plant growth, and plant stress tolerance. We investigated the efficacy of a PGPR species with rhizosphere acidification potential, named Bacillus sp. ZV6 (ARB), in enhancing Ni phytoextraction by white willow (Salix alba) from a Ni-affected soil. The plants were grown for 120 days in soil with zero, threshold, and moderate Ni pollution levels (0, 50, and 100 mg Ni kg−1 soil, respectively) with and without ARB inoculation. After harvest, the effects of the treatments on rhizosphere acidification and associated Ni bioavailability in this zone, Ni distribution in plants, and Ni removal from the soil were investigated. Moreover, enzyme activity, count of bacteria, biomass of microbes, and organic C in the soil, together with indices of plant growth and antioxidant defense, were evaluated. The ARB inoculation significantly improved the plant parameters and soil health and reduced plant oxidative stress at each Ni level compared to the treatments lacking ARB. Besides lowering the soil pH and increasing Ni bioavailability in the rhizosphere with respect to the bulk zone, ARB inoculation exerted additional effects. Surprisingly, the Ni 100 + ARB treatment induced the highest decrease in soil pH (0.32 unit) and an increase in DPTA-extractable Ni (0.45 mg kg−1 soil) between that measured in the bulk zones and that obtained in the rhizosphere zone. Ni distribution in plant parts and Ni removal (% of total Ni) from the soil were also significantly improved with ARB inoculation, compared to the Ni treatments without ARB. The extent of Ni removal was similar for the Ni 50 + ARB (0.27%) and Ni 100 + ARB (0.25%) treatments. Concluding, ARB-inoculated Salix alba can remove similar amounts of Ni from the soil, irrespective of the Ni pollution level.

Ni(II) and Pb(II) Removal Using Bacterial Cellulose Membranes.

Bacterial cellulose (BC) is a highly crystalline nanosized material with a high number of active groups. This study focuses on the synthesis of BC membranes through fermentation, their characterization and application to remove Ni(II) and Pb(II) from wastewater by adsorption under different conditions. Four-day-grown BC membranes form three-dimensional nanofibril networks with a pH of 6.3 and a high cationic demand (52.5 μeq·g-1). The pseudo-second-order kinetic model and the Sips isotherm model best describe the adsorption of both metals. The intraparticle diffusion model of Ni(II) revealed a three-step mechanism of adsorption-plateau-adsorption, while Pb(II) adsorption followed a typical reducing-slope trend up to saturation. The highest removal of Ni(II) and Pb(II) was obtained at pH 4 with a BC dosage of 400 mg·L-1. The maximum adsorption capacities were 28.18 mg·g-1 and 8.49 mg·g-1 for Ni(II) and Pb(II), respectively, involving the total coverage of the material active sites. Thermodynamically, Ni(II) adsorption was exothermic, and Pb(II) was endothermic. The obtained values of sorption heat, activation and Gibbs' energy depicted a physisorption process. Ni(II) removal mechanism was ruled by crystallization on the metals adsorbed on the BC active groups, while Pb(II) was driven by the adsorption process, as shown by TEM images of the spent material.

The Potential Efficiency of Bacillus subtilis AIK to Remove Nickel from Aqueous Solutions

In this study a new strain of mesophilic Bacillus subtilis AIK, recorded for the first time in Iraq, was used to remove nickel (Ni) from aqueous solutions. The factors that affect bioremediation include temperature, pH value and metal concentrations. The results showed that the highest removal efficiency (R%) was 54, 52 and 48% at 25⁰C and pH of 5, 7 and 9, and with 10 ppm Ni concentration respectively. Whereas the highest R% recorded was 47, 45 and 52% at 30⁰C and of pH 5, 7, and 9 with 1 ppm Ni concentration respectively. On the other hand, the highest R% at 40⁰C was 49, 46, 42 % at pH 5, 7 and 9, with 5, 10 and 10 ppm Ni concentrations respectively. The results also showed that the optimum pH value for Ni removal at both 25 and 40⁰Cwas 5, while at 30⁰C it was 9. The optimum temperature was kept at 25⁰C. In general, B. subtilis AIK showed an admissible capacity to remove Ni from aqueous solutions.

Removal of Ni2+ ions from Contaminated Water by New Exopolysaccharide Extracted from K. oxytoca J7 as Biosorbent

Removal of Ni2+ ions from Contaminated Water by New Exopolysaccharide Extracted from K. oxytoca J7 as Biosorbent

Electrochemical Removal of Metal-Organic Complexes in Metal Plating Wastewater: A Comparative Study of Cu-EDTA and Ni-EDTA Removal Mechanisms.

Cu and Ni complexes with ethylenediaminetetraacetic acid (Cu/Ni-EDTA), which are commonly present in metal plating industry wastewaters, pose a serious threat to both the environment and human health due to their high toxicity and low biodegradability. In this study, the treatment of solutions containing either or both Cu-EDTA and Ni-EDTA using an electrochemical process is investigated under both oxidizing and reducing electrolysis conditions. Our results indicate that Cu-EDTA is decomplexed as a result of the cathodic reduction of Cu(II) with subsequent electrodeposition of Cu(0) at the cathode when the cathode potential is more negative than the reduction potential of Cu-EDTA to Cu(0). In contrast, the very negative reduction potential of Ni-EDTA to Ni(0) renders the direct reduction of EDTA-complexed Ni(II) at the cathode unimportant. The removal of Ni during the electrolysis process mainly occurs via anodic oxidation of EDTA in Ni-EDTA, with the resulting formation of low-molecular-weight organic acids and the release of Ni2+, which is subsequently deposited as Ni0 on the cathode. A kinetic model incorporating the key reactions occurring in the electrolysis process has been developed, which satisfactorily describes EDTA, Cu, Ni, and TOC removal. Overall, this study improves our understanding of the mechanism of removal of heavy metals from solution during the electrochemical advanced oxidation of metal plating wastewaters.

Efficient removal of Ni(II) by nanosecond pulsed discharge‐modified resins: Characterization, capacity, and kinetics

AbstractA porous functionalized resin was produced using nanosecond pulsed discharge for the purpose of removing Ni(II). The implications of discharge time, O2 concentration, and solution pH on adsorption capacity were explored. Studies indicated that nanosecond pulsed discharge‐modified resins in 5 min of discharge time and 8% of O2 concentration had a removal efficiency of 97.2%, and an increase of 36% compared to the raw. Furthermore, the residual Ni(II) concentration (0.3 mg/L) is well below the national permitted emission standard (0.5 mg/L). The rise in Ni(II) removal efficiency is associated with the increased specific surface area and oxygen‐containing functional groups. Chemisorption played an important role in the removal of Ni(II) by raw and modified resins.

Deep insight on mechanism and contribution of arsenic removal and heavy metals remediation by mechanical activation phosphogypsum

Arsenic-containing wastewater and arsenic-contaminated soil can cause serious environmental pollution. In this study, phosphogypsum with partial mechanical activation of calcium oxide was used to prepare a new phosphogypsum-based passivate (Ca-mPG), and its remediation performance on arsenic-contaminated soil was evaluated in terms of both effectiveness and microbial response. The results showed that the optimum conditions for the preparation of the passivate were optimized in terms of single factor and response surface with a ball milling speed of 200 r/min, a material ratio of 6:4 and a ball milling time of 4 h. Under these conditions, the adsorption capacity was 37.75 mg/g. The leaching concentration of arsenic (As) in the contaminated soil after Ca-mPG modification decreased from 25.75 μg/L to 5.88 μg/L, which was lower than the Chinese national standard (GB/T 5085.3–2007); Ca-mPG also showed excellent passivation effect on other heavy Metals (copper, nickel, cadmium, zinc). In addition, As-resistant bacteria and passivators work together to promote the stabilization effect of contaminants during the remediation of As-contaminated soil. The mechanisms of Cu, As(III)/As(V), Zn, Cd, and Ni removal were related to ion exchange, electrostatic adsorption of substances on heavy metals, calcium binding to other substances to produce precipitation; and microbially induced stabilization of HMs, oxidized. Overall, this study demonstrates an eco-friendly "waste-soil remediation" strategy to solve problems associated with solid waste reuse and remediation of HM-contaminated soils.

Comparative investigation on Ni(II) removal from electroplating wastewater by mineral adsorbent (CSAM) and ion-exchange resins

ABSTRACT The efficiency of Ni(II) removal from electroplating wastewater is highly correlated with different adsorption materials. A Ca-Si activated mineral adsorbent (CSAM) and two ion-exchange resins (732 and D152) were compared. The adsorption of Ni (II) by three materials is spontaneous and endothermic, and their adsorption capacities are similar (48.66–65.36 mg/g at 318K), but the dosage of CSAM is less (1.0 g/L for 50 mg/L Ni(II)), its adsorption is faster (<5 min) and pH range is wider (2–7). 10% NaCl, 1 mol/L HCl and 10% NaCl +1 mol/L HCl were used as desorbent agents, and CSAM exhibited an extremely low desorption rate (1.49–3.41%). The smaller separation factor (close to 0) and XPS analysis showed that the Ni(II) adsorption on CSAM was an irreversible chemical process, which was different from the three-stage adsorption of resins. The treatment of two kinds of electroplating wastewater with high and low concentration showed that CSAM not only had a higher Ni(II) removal rates (>98.4%), but also could efficiently remove Cu(II) (>98%), total-chromium (>79%) and COD (>66%). The treatment of Ni(II) containing electroplating wastewater with ion-exchange resins is greatly affected by the complexing agent. CSAM is more suitable for the treatment of electroplating wastewater containing various metals and organic matters.

Potential of sludge-derived char as a metal sorbent during primary settling of municipal wastewater

Reuse of nutrients and water from municipal wastewater is attracting increasing attention. However, pollutants such as toxic metals should be minimised. This study investigated the potential for reducing metal concentrations in wastewater effluent and secondary sludge by introducing sludge-derived char (SDC) as a sorbent in primary settling. Batch experiments, performed in aqueous metal solution and wastewater, showed that Cu and Ni removal was significantly reduced in wastewater containing dissolved organic matter (68% and 40%, respectively), compared to metal solution (>99% and 99%, respectively). Modelling of primary settling indicated Cd and Cu removal enhancement with SDC addition (from 39%–79% and 30%–43%, respectively). Smaller effects were observed for Pb, Cr, and Zn. An increased risk of Ni concentration in primary settler effluent was identified (−53% removal). These results demonstrate the challenges of implementing SDC as a sorbent for real wastewater.

Bottom-Up Synthesis of an Oligo-dithiocarbamate Chelating Precipitant and Its Direct Removal of Complexed Heavy Metals from Acidic Wastewater

Complexed heavy metal (HM) in acidic wastewater is one of the toughest issues for environmental pollution control. Aimed at directly eliminating complexed HMs from acidic wastewater, a novel cost-effective oligo-dithiocarbamate (oligo-DTC) chelating precipitant was synthesized by a bottom-up method from ammonia and 1,2-dichloroethane (DCE). Synthesis conditions were systematically optimized based on Ni removal performance at pH 2 and pH 7. An NH3/DCE ratio of 3:1 or above at temperatures between 100 and 160 °C were suitable for amination, while a NaOH/DCE ratio of 0.5–1.0:1 and a CS2/DCE ratio of 1.0:1 were favorable for dithiocarbamylation. The theoretical S/Ni mole ratio of oligo-DTC, representing the theoretically required oligo-DTC dose for complete Ni removal, was 8.2–9.4 at pH 2 and 4.0–4.6 at pH 7. Oligo-DTC showed high removal efficiencies for various HMs and had advantages over similar DTCs with high synthesis costs. Oligo-DTC successfully removed complexed HMs from two typical acidic wastewaters with residual HMs below the stringent discharge limits. Oligo-DTC had an average molecular weight of 1150 Da based on LCHRMS. Characterizations (scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy) showed that oligo-DTC removed HMs by chelation with its NCS2– functional groups and also indicated that oligo-DTC suffered nonnegligible self-aggregation and decomposition in HM removal under strongly acidic conditions.

Removal Performance and Mechanism of Potassium Permanganate Modified Coconut Shell Biochar for Cd(Ⅱ) and Ni(Ⅱ) in Aquatic Environment

In this study, coconut shell biochar modified by KMnO4 (MCBC) was used as the adsorbent, and its removal performance and mechanism for Cd(Ⅱ) and Ni(Ⅱ) were discussed. When the initial pH and MCBC dosage were separately 5 and 3.0 g·L-1, respectively, the removal efficiencies of Cd(Ⅱ) and Ni(Ⅱ) were both higher than 99%. The removal of Cd(Ⅱ) and Ni(Ⅱ) was more in line with the pseudo-second-order kinetic model, indicating that their removal was dominated by chemisorption. The rate-controlling step for Cd(Ⅱ) and Ni(Ⅱ) removal was the fast removal stage, for which the rate depended on the liquid film diffusion and intraparticle diffusion (surface diffusion). Cd(Ⅱ) and Ni(Ⅱ) were mainly attached to the MCBC via surface adsorption and pore filling, in which the contribution of surface adsorption was greater. The maximum adsorption amounts of Cd(Ⅱ) and Ni(Ⅱ) by MCBC were individually 57.18 mg·g-1 and 23.29 mg·g-1, which were approximately 5.74 and 6.97 times that of the precursor (coconut shell biochar), respectively. The removal of Cd(Ⅱ) and Zn(Ⅱ) was spontaneous and endothermic and had obvious thermodynamic characteristics of chemisorption. Cd(Ⅱ) was attached to MCBC through ion exchange, co-precipitation, complexation reaction, and cation-π interaction, whereas Ni(Ⅱ) was removed by MCBC via ion exchange, co-precipitation, complexation reaction, and redox. Among them, co-precipitation and complexation were the main modes of surface adsorption of Cd(Ⅱ) and Ni(Ⅱ). Additionally, the proportion of amorphous Mn-O-Cd or Mn-O-Ni in the complex may have been higher. These research results will provide important technical support and theoretical basis for the practical application of commercial biochar in the treatment of heavy metal wastewater.

Enhanced effect and mechanism of nano Fe-Ca bimetallic oxide modified substrate on Cu(II) and Ni(II) removal in constructed wetland

In this study, Fe2O3 nanoparticles (Fe2O3 NPs) and CaO NPs were loaded on the zeolite sphere carrier to create nano Fe-Ca bimetallic oxide (Fe-Ca-NBMO) modified substrate, which was introduced into constructed wetland (CW) to remove Cu(II) and Ni(II) via constructing "substrate-microorganism" system. Adsorption experiments showed that the equilibrium adsorption capacities of Fe-Ca-NBMO modified substrate for Cu(II) and Ni(II) were respectively 706.48 and 410.59 mg/kg at an initial concentration of 20 mg/L, 2.45 and 2.39 times of gravel. The Cu(II) and Ni(II) removal efficiencies in CW with Fe-Ca-NBMO modified substrate respectively reached 99.7% and 99.9% at an influent concentration of 100 mg/L, significantly higher than those in gravel-based CW (47.0% and 34.3%). Fe-Ca-NBMO modified substrate could promote Cu(II) and Ni(II) removal by increasing electrostatic adsorption, chemical precipitation, as well as the abundances of resistant microorganisms (Geobacter, Desulfuromonas, Zoogloea, Dechloromonas, and Desulfobacter) and functional genes (copA, cusABC, ABC.CD.P, gshB, and exbB). This study provided an effective method to enhance Cu(II) and Ni(II) removal of electroplating wastewater by CW with Fe-Ca-NBMO modified substrate.

Approaches to Enhancing Cathodic Nickel Recovery from Ni-EDTA Containing Synthetic Wastewaters

Ethylenediaminetetraacetic acid (EDTA) is widely employed as a chelating agent in the electroless nickel plating industry to form stable metal–organic complexes (e.g., Ni-EDTA). These metal–organic complexes cannot be removed from plating wastewaters by traditional treatments in a cost-effective way. While electrochemical advanced oxidation processes (EAOPs) have been utilized for the efficient degradation of Ni-EDTA at the anode, challenges remain in the simultaneous and effective recovery of nickel at the cathode. In this study, we investigate the efficacy of five cathode materials [i.e., carbon felt (CF), titanium plate, graphite plate (GP), copper plate, and stainless-steel plate] with respect to Ni recovery. The highest Ni removal efficiency of 81.6 ± 0.1% was achieved with the carbon felt cathode which was 30% higher than that of the titanium cathode (52.1 ± 1.4%) with the improvement in performance attributed to the higher rate of mass transport of Ni ions (CF: 4.3 ± 0.4 × 10–4 s–1 vs Ti: 1.8 ± 0.2 × 10–4 s–1) toward the nanowire structure of carbon felt and to the large surface area of the carbon felt cathode compared with the other cathodes. While the chemical composition of the deposits was independent of the cathodic material or structure, the morphology of deposition varied with the cathode material. The accumulated Ni on the carbon felt surface was successfully recovered either as a nickel salt solution by acid leaching or as high purity NiO by calcinating the Ni-loaded carbon felt cathode at over 800 °C. The performance of the regenerated carbon felt after acid leaching was comparable to that of the fresh cathode even after 10 cycles of use and regeneration via acid leaching with this result confirming the stability and reusability of the carbon felt material.

Adsorption of toxic metals from landfill leachate onto guinea fowl eggshells in the era of green chemistry

One of the best and most affordable ways to remove harmful metals from water is by adsorption. This study investigated the efficiency of guinea fowl (Numida meleagris) eggshells as a low-cost adsorbent for cadmium (Cd) and nickel (Ni) removal from landfill leachate. In replicas, 100 mL wastewater was added to each of the weighed adsorbent dosages (1 g, 1.5 g, 2 g, 2.5 g, 3.0 g, and 3.5 g) in a flat-bottom flask and agitated for 60 minutes at pH of 7.82 and temperature 24 °C. The adsorption efficacy of cadmium and nickel by guinea fowl eggshells were 90.5% to 96.5% and 96.1% to 99.3%, respectively. The maximum adsorption capacity of cadmium was 4.89 × 10-2 mg/g and an adsorption equilibrium (KL) 22.74 mg/L. The Langmuir isotherm model was better fitted to the results of the experiment than the Freundlich isotherm model.