Removal Efficiency Of Cu Research Articles

Non-Linear Regression Model for Estimating the Efficiency of Heavy Metals Removal by Soil Washing with Chitosan Solution

The process of heavy metals removal by soil washing using chitosan as washing agent is a multivariate problem. According to the experimental data sets obtained during experiments performed at laboratory scale, the main parameters that influenced the efficiency of the soil washing process were the stirring time of the polluted soil with the investigated washing agent, washing solution concentration, and solid/liquid ratio (S/L ratio). This study explores the statistical relationships between the removal efficiency of Cu and Pb from polluted soil by washing with chitosan and factors influencing the soil washing process by use of a non-linear regression model. The non-linear regression model contains a non-linear component and a component of interaction among the two parameters (S/L ratio “X1”, the stirring time “X2”) which influences the efficiency of the Cu and Pb removal from soil by soil washing with the investigated washing agent. The proposed model is useful for predicting and estimating the effectiveness of the soil decontamination process by washing with chitosan. A comparison between the data calculated using the proposed mathematical model and the experimental data was also performed in order to determine the integrity and conformity of the mathematical model obtained. The results showed a good fit of the obtained model to the experimental data.

Simultaneous removal of Cu (II) and Cr (VI) ions from petroleum refinery wastewater using ZnO/Fe3O4 nanocomposite

The presence and removal of heavy metals such as Cu(II) as well as Cr(VI) in petroleum refinery wastewater calls for concerted efforts due to their mobility, toxicity, bioaccumulation, and non-biodegradability in the environment. In this present work, zinc oxide (ZnO), iron oxide (Fe3O4) nanoparticles and ZnO/Fe3O4 nanocomposites were synthesized via simple sol-gel and chemical reduction methods; characterized using different analytical tools and then applied as nanoadsorbent to sequester Cu(II) and Cr(VI) ions from Petroleum Refinery wastewater via batch adsorption process. Cu(II) and Cr(VI) adsorption processes were examined with respect to contact time (kinetic effect), nanoadsorbent dosage, isotherm equilibrium, and thermodynamic parameters. ZnO/Fe3O4 nanocomposites with higher surface area (39.450 m2/g) have a mixture of rod-like and spherical shapes as compared to ZnO and Fe3O4 nanoparticles with spherical shape only and surface areas of 8.62 m2/g and 7.86 m2/g) according to the high-resolution scanning electron microscopy (HRSEM) and Brunauer–Emmett–Teller (BET) analysis. The X-ray diffractometer (XRD) results revealed the formation of hexagonal wurtzite structure of ZnO and the face-centered cubic structure phase of Fe3O4 nanoparticles, after the formation of the ZnO/Fe3O4 nanocomposites the phases of the nanoparticles were not affected but the diffraction peaks shifted to higher 2θ degree. The average crystallite size of ZnO and Fe3O4 nanoparticles and ZnO/Fe3O4 nanocomposites were 20.12, 26.36 and 14.50 nm respectively. The maximum removal efficiency of Cu (II) (92.99%) and Cr (VI) (77.60%) by ZnO/Fe3O4 nanocomposites was higher than 85.83%; 65.19% for Cu (II) and 80.57%; 62.53 for Cr (VI) using ZnO and Fe3O4 nanoadsorbents individually under the following conditions: contact time (15), dosage (0.08 g) and temperature (30 °C). The experimental data for Cu (II) and Cr (VI) ion removal fitted well to the pseudo-second-order kinetic and Langmuir isotherm models. The thermodynamic study suggested that the removal of the two metal ions from petroleum wastewater was endothermic. The reusability study after the fourth adsorption-desorption cycle indicated the stability of ZnO/Fe3O4 nanocomposites with 85.51% and 69.42% removal efficiency of Cu (II) and Cr (VI). The results showed that ZnO/Fe3O4 nanocomposite achieves higher performance than ZnO and Fe3O4 alone in the removal of Cu (II) and Cr (VI) ions from the petroleum refinery wastewater.

Optimization of a High-Pressure Soil Washing System for Emergency Recovery of Heavy Metal-Contaminated Soil

Recent natural disasters, such as typhoons in South Korea and other countries around the globe, have resulted in loss of human life and damage to property, often causing contamination of nearby soil environments. This study focused on the emergency recovery of soil contaminated by heavy metals following a disaster such as typhoon flooding by applying a soil washing technique that used high-pressure water rather than chemical cleaning agents. Artificially contaminated soil containing 700 mg/kg Cu, 530 mg/kg Pb and 900 mg/kg Zn, was used. All three metals were present at levels higher than the Korean Warning Standards (500 mg/kg Cu, 400 mg/kg Pb, 600 mg/kg Zn) for region 2 (miscellaneous area). A high-pressure soil washing device was designed to treat 0.6 tons/h and optimal treatment was sought for varying levels of pressure (1, 3, 5 MPa), solid to liquid ratios (S/L) (1:1, 1:3, 1:5), and number of washing cycles (1, 2, 3). The high-pressure soil washing results showed that a 5 MPa washing pressure, 1:1 solid-liquid ratio, and one washing cycle were the optimum conditions to generate the highest heavy metal removal rates. Under optimal conditions, high-pressure soil washing attained removal efficiencies of Cu (37.7%), Pb (36.6%), and Zn (45.1%), and the residual concentrations of heavy metals in the remediated soil satisfied the Korean Warning Standard (Region 2). A comparison of the changes in particle size showed that after high-pressure washing, the mass fraction of coarse sand (CS, 2–0.42 mm) decreased by 23.3%, while that of fine sand (FS, 0.42–0.074 mm), silt, and clay (SC, <0.074 mm) increased by 4.2% and 19.1%, respectively. In addition, 31.1–34.6% of the CS heavy metal mass loading shifted to FS and SC fractions after washing. A comparative analysis of the soil surface morphology before and after washing using scanning electron microscopy (SEM) showed that the particles in the remediated soil became noticeably cleaner after high-pressure washing. This study demonstrated the feasibility of emergency recovery of heavy metal-contaminated soil using high-pressure washing without a chemical cleaning agent.

The separation behavior of impurity in antimony during vacuum distillation

The models for depicting the variation tendencies of contents of Cu, Fe, Ni, Pb and Bi impurities in melt and distillate were established. The results proved that the mass transfer process was determined by the hybrid steps of mass transfer processes in the liquid boundary layer and at the liquid-gas interface for Pb and Bi impurities, whereas the rate-determining step was the mass transfer process at the liquid-gas interface for Cu, Fe and Ni impurities. The experimental results of Cu, Fe, Ni and Pb impurities in melt were coincident with the calculated results, while the experimental result was lower than the calculated result for the Bi impurity; the experimental result of Bi impurity in distillate was consistent with the calculated result, whereas there existed discrepancy for the Pb impurity; the marked increases of keff of Pb and Bi impurities during distillation were responsible for the difference between the experimental and calculated results in distillate. Additionally, the removal efficiencies of Cu, Fe and Ni impurities were higher than those of Pb and Bi impurities, the reason arose from that the vapor pressures of the latter were much closer to that of antimony than those of the former.

Role of calcium carbonate in the process of heavy metal biosorption from solutions: synergy of metal removal mechanisms

The effect of calcium carbonate on the removal efficiency of cations of the selected heavy metals Cu, Zn and Pb from aqueous solutions using various biosorbents (BS) was investigated under laboratory static conditions. The main mechanism of biosorption of heavy metal cations is ion exchange, whereas the reaction with calcium carbonate results in precipitation of poorly soluble carbonates and hydroxides of the examined heavy metals. Studies conducted under static conditions have shown that the effect of Cu and Zn cations removal from solutions is better when using a mixture of BS and CaCO3 as compared to the effect of process, in which these two components were used separately. Removal efficiency for Cu and Zn has been shown to increase from 20 to 50% depending on the BS used. For the removal of lead cations, a measurable effect is found only for biosorbents whose active centers are saturated with protons (improvement in removal efficiency by about 20%). A synergy effect in the flow system was also investigated. It was found that under the conditions of the experiment, the addition of powdered CaCO3, in a weight ratio of 1 g CaCO3: 15 g BS, increases the removal efficiency of all the metals studied by 20–30%. It has been shown that an important role in the process of heterophasic ion exchange is played by neutralization of protons—desorbed from the biosorbents—with hydroxide ions released into the solution by partial dissolution of CaCO3 and subsequent hydrolysis reaction.

Development of a Unique Technology for the Pyrolysis of Rice Husk Biochar for Promising Heavy Metal Remediation

Due to anthropogenic activities, potentially toxic elements cause severe soil pollution worldwide. Therefore, remediation of contaminated soils is exigent and imperative. One cost-effective and environmentally friendly remediation approach is the application of biochar, which is a solid carbonaceous material. Biochar degrades slowly in soil and can persist there for thousands of years, according to various estimations. In addition, coal obtained from crop wastes has a developed porous structure, a high specific surface area, and does not contain toxic compounds such as heavy metals and polycyclic aromatic hydrocarbons. Biochar with optimal values for specific surface area and porosity was obtained from rice husk by stepwise pyrolysis. The pyrolysis parameters such as the heating rate (11 °C∙min−1), temperature (700 °C), and holding time (45 min) were established. At the same time, the surface area of the biochar increased by almost three times with a change in the pyrolysis conditions. As a part of this research, the efficacy of adsorption of Cu(II) from Haplic Chernozem using biochar made from rice husk was examined. The Langmuir and Freundlich models were employed to describe the adsorption data. The isotherm data of heavy metals was better fitted to the Langmuir adsorption model. The addition of rice husk biochar to the soil presented greater removal efficiencies of Cu(II) than soil in pure form. The analysis of the structural characteristics of the sorbent suggest that this material may work efficiently for the restoration of contaminated soil.

MOF-derived N-Co/Fe-PC composite as heterogeneous electro-Fenton catalysis combined with electrocoagulation process for enhanced degradation of Cu-CIP complexes from wastewater

Recently, heavy metal-antibiotic complexes have been frequently detected in wastewater, posing a serious threat to the human health. In this study, a novel combination of heterogeneous electro-Fenton (hetero-EF) and electrocoagulation process was developed for efficient removal of Cu-ciprofloxacin complexes (Cu-CIP). As hetero-EF cathode catalyst, N doped porous carbon loaded with Co/Fe sites (N-Co/Fe-PC) was innovatively synthesized, and Fe/CoNC structure was formed. The homogeneous mixing of Fe3C and Co3Fe7 resulted in the electron transfer and accumulation on Fe3C, which optimized the active substance and facilitated the oxygen reduction reaction. The effects of current, electrolyte type, pH, and concentration were comprehensively investigated, and the optimum removal efficiency of Cu, CIP, and TOC were 99.69 %, 96.40 %, and 83.62 %, respectively. Besides, it revealed that ·O2– was the dominant contributor to the Cu-CIP degradation. As a result, Cu-CIP complexes were degraded into small molecules and released Cu2+ with the ring-opening demethylation of the piperazine ring, cleavage and demethylation of carboxyl group, hydroxylation of the piperazine ring, and β-cleavage reactions of cyclopropyl group. Meanwhile, they were also adsorbed by aluminum hydroxide/hydroxyl oxides especially γ-AlOOH generated from the anode and finally coprecipitated. This study will provide a novel technology and theoretical basis for enhanced degradation of heavy metal-antibiotic complexes from wastewater.

Selective recovery of Cu(II) from strongly acidic wastewater by zinc dimethyldithiocarbamate: Affecting factors, efficiency and mechanism

The selective recovery of copper from strongly acidic wastewater containing mixed metal ions remains a significant challenge. In this study, a novel reagent zinc dimethyldithiocarbamate (Zn(DMDC)2) was developed for the selective removal of Cu(II). The removal efficiency of Cu(II) reached 99.6% after 120 min reaction at 30°C when the mole ratio Zn(DMDC)2/Cu(II) was 1:1. The mechanism investigation indicates that the Cu(DMDC)2 products formed as a result of the displacement of Zn(II) from the added Zn(DMDC)2 by Cu(II) in wastewater, due to the formation of stronger coordination bonds between Cu(II) and the dithiocarbamate groups of Zn(DMDC)2. Subsequently, we put forward an innovative process of resource recovery for strongly acidic wastewater. Firstly, the selective removal of Cu(II) from actual wastewater using Zn(DMDC)2, with a removal efficiency of 99.7%. Secondly, high-value CuO was recovered by calcining the Cu(DMDC)2 at 800°C, with a copper recovery efficiency of 98.3%. Moreover, the residual As(III) and Cd(II) were removed by introducing H2S gas, and the purified acidic wastewater was used to dissolve ZnO for preparation of valuable ZnSO4·H2O. The total economic benefit of resource recovery is estimated to be 11.54 $/m3. Accordingly, this study provides a new route for the resource recovery of the treatment of copper-containing acidic wastewater.

Exogenous Pseudomonas aeruginosa application improved the phytoremediation efficiency of Lolium multiflorum Lam on Cu–Cd co-contaminated soil

Pot experiments were conducted to explore the effect of Pseudomonas aeruginosa on the phytoremediation efficiency of ryegrass on jointly Cu- and Cd-contaminated soil. P. aeruginosa application promoted the growth of ryegrass, increased the concentration of Cu and Cd in ryegrass, and enhanced the translocation of Cu and Cd from roots to shoots. The biomass of ryegrass in the T7 treatment increased by 43.1% compared to the T1 treatment. Additionally, P. aeruginosa application improved the bioavailability of Cu and Cd. The concentration of Cu and Cd in ryegrass under the T7 treatment was 48.7% and 32.8% higher than that under the T1 treatment, and the removal efficiencies of Cu and Cd from soil under the T7 treatment reached 89.5% and 89.3%, respectively. The subcellular distribution of Cu and Cd in ryegrass indicated that Cu and Cd were mainly distributed in the cell wall and cell-soluble fraction, and a large amount of Cd entered the shoot cell membrane and organelle-containing fraction under 500 mg⋅kg−1 P. aeruginosa culture application. Thus, application of 500 mg⋅kg−1P. aeruginosa culture to soil can enhance Cu uptake by ryegrass, and the maximum capacity of ryegrass to absorb Cd from the soil was reached with 50 mg⋅kg−1P. aeruginosa culture application. In light of the above results, P. aeruginosa culture application facilitated the phytoremediation of Cu–Cd co-contaminated soil by ryegrass.

Adsorptive properties of MgO/WO3 nanoadsorbent for selected heavy metals removal from indigenous dyeing wastewater

The magnesium oxide/tungsten trioxide (MgO/WO3) nanocomposites were prepared at different mixing ratios using a combination of green and wet impregnation methods and subsequently utilized as nanoadsorbent for the removal of selected heavy metals from Indigenous dyeing wastewater. The synthesized nanomaterials were characterized using High-resolution electron microscopy (HRSEM), High-resolution transmission electron microscopy (HRTEM), Energy Dispersive Spectroscopy (EDS), Selective Area Diffraction (SAED), X-ray diffraction (XRD) and Brunauer Emmett-Teller (BET) N2 Adsorption-desorption method. HRSEM/HRTEM analysis demonstrated the formation of a distinct spherical shape irrespective of the mixing ratio of MgO on WO3 nanoparticles. XRD analysis confirmed the existence of a monoclinic phase and face centred cubic phase for WO3 and MgO nanoparticles and strong interaction between the nanoparticles leading to the formation of magnesium tungstate (MgWO4). The BET analysis revealed a higher surface area (104.2 m2/g) for mesoporous MgO/WO3 nanocomposite with a mixing ratio (4:1) than WO3 alone with a surface area (22.5 m2/g). The maximum removal efficiency of Cu(II) (98.1%), Fe(II) (100%) and Cr(VI) (100%) was achieved at an optimum contact time of 12, 12 and 14 min respectively. The adsorption data evaluated using Langmuir, Freundlich and Temkin models showed that experimental data best fitted the Langmuir model while the fitness of adsorption data to different kinetic models followed pseudo-second-order. The adsorption of the selected metal ion using MgO/WO3 nanoadsorbent was based on electrostatic attraction, ion exchange, and pore diffusion mechanism. The thermodynamic study demonstrated the endothermic and spontaneous nature of the metal sorption process. MgO/WO3 nanoadsorbent with a mixing ratio (4:1) exhibited greater adsorption efficiency than other nanoadsorbents and has excellent regeneration potentials after 5 cycles.

Preparation of a novel composite geopolymer based on calcium carbide slag-fly ash and its characterization, mechanism and adsorption properties.

In this study, a mixed precursor system of fly ash (50 wt%) and calcium carbide slag (50 wt%) was used to prepare a geopolymer, and the hydration and hardening mechanism of the whole system and the microscopic characterization of the calcium carbide-fly ash based polymer were investigated after the addition of calcium carbide slag. Ca(OH)2 in calcium carbide slag can effectively excite the volcanic ash activity of fly ash, which leads to a more adequate geopolymerization reaction and produces more hydrated calcium silicate (C-S-H) gels. These gels have very high specific surface area and surface adsorption energy. The results showed that the specific surface area of geopolymer was as high as 79.76 m2/g, and through the study of its adsorption capacity of Cu(II) in aqueous solution, the results showed that its removal efficiency of Cu(II) was 97.63% and its adsorption capacity was 58.58 mg/g. By using fly ash and calcium carbide slag as the auxiliary raw materials for the preparation of geopolymer, it not only can promote the reaction of proceeding, but can also act as an excellent adsorption material, and also as an effective way to utilize industrial waste resources.

Synthesis of Microporosity Dominant Wood-Based Activated Carbon Fiber for Removal of Copper Ions.

Steam activation treatments were introduced in the preparation of activated carbon fiber from liquefied wood (LWACF), to enlarge its specific surface area and develop the pore size distribution. With increasing activation time, the average fiber diameter of LWACF decreased from 27.2 µm to 13.2 µm, while the specific surface area increased from 1025 to 2478 m2/g. Steam activation predominantly enhanced the development of microporosity, without significant pore widening. Prolonging the steam activation time exponentially increased the removal efficiency of Cu2+ at a constant adsorbent dose, as a result of an increase in the number of micropores and acidic-oxygenated groups. Moreover, for LWACF activated for 220 min at 800 °C, the removal efficiency of Cu2+ increased from 55.2% to 99.4%, when the porous carbon fiber dose went from 0.1 to 0.5 g/L. The synthesized LWACF was proven to be a highly efficient adsorbent for the treatment of Cu2+ ion-contaminated wastewater.

Performance of Treated and Untreated Spent Coffee Ground on the Removal of Cu (II) in Aqueous Solution: A Comparative Study

The performance of two types of spent coffee ground (SCG), (i) untreated spent coffee ground (USCG) and (ii) acid-treated spent coffee ground (TSCG) on the Cu (II) removal from aqueous solution was investigated and compared in this study. The effects of operating parameters such as pH, contact time and initial Cu (II) concentration on the adsorption rate were studied in batch adsorption mode. The USCG showed better results than the TSCG. The highest removal efficiency of Cu (II) (50 mg/L) by USCG was 91.03% with an adsorption capacity of 45.52 mg/g, which was achieved at pH 6 and 90 min of contact time. The TSCG showed lower performance with a removal efficiency of 44.18% and adsorption capacity of 37.06 mg/g. This may be due to the flushed off in the functional groups of SCG that used for metal binding in the adsorption during acid treatment and the existence of Cl- ions on the TSCG surface, interfering the Cu (II) adsorption and reduces its adsorption capacity. Freundlich fitted well with the equilibrium data for copper (II) removal, as indicated by the R2 coefficient, for USCG and TSCG were 0.9912 and 0.9622, respectively. These data indicate that both USCG and TSCG have high sorption capacity and affinity for metal ions. The USCG showed a better Cu (II) removal than the TSCG, indicating a promising function as a low-cost natural adsorbent for Cu (II) and also other heavy metals removals.

Removal of Copper(II) Ion using Nanochitosan/Carboxymethyl Cellulose/Grapheme Oxide Composite Biosorbent

The present study aimed to prepare a novel biosorbent of nanochitosan (NCS)/carboxymethyl cellulose (CMC)/graphene oxide (GO) and used to remove Cu(II) ion from wastewater system. The prepared nanocomposite was characterized using FTIR, XRD and SEM analysis. The FTIR and XRD results revealed the formation of novel NCS/CMC/GO nanocomposite. Rough surface morphology of nanocomposite was confirmed from the SEM analysis results. The removal efficiency of Cu(II) ion was evaluated through batch mode by varying pH, adsorbent dose, contact time and initial metal ion concentration. The maximum removal of Cu(II) ion was 80.1% at pH 4, 92.4% at 360 min contact time and about 89.2% for 3 g adsorbent dose. Theoretical models such as Langmuir isotherm, Freundlich isotherm, and kinetics models were used to evaluate the experimental results. After examining, the results revealed that the adsorption follows Freundlich isotherm and pseudo-second-order models. The adsorption capacity of the prepared nanocomposite was 145.22 mg/g.

Effect of coexisting metal ions on bio-precipitation of Cu<sup>2+</sup> phosphate by Rahnella sp. LRP3 and its stability in soil

The phosphate precipitation of heavy metal induced by microorganisms plays an important role in immobilising heavy metal in soil. However, there is little knowledge about the effect of coexisting metal ions on the induction of Cu phosphate mineral and its stability. In this paper, the Cu phosphate precipitations, coexisting with Pb<sup>2+</sup> or Ca<sup>2+</sup> induced by strain LRP3, were characterised, and the stabilisation of the induced phosphate precipitates was also studied. The coexistence of Cu with Pb or Ca decreased the removal efficiency of Cu<sup>2+</sup> by 17.18% and 9.78%, respectively, indicating the competitive adsorption between cations. Strain LRP3 could induce a new phosphate mineral of CuCa<sub>10</sub>(PO<sub>4</sub>)<sub>7</sub> when coexisting with Ca and also generate the phosphate minerals of Pb(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub> and Cu<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> when coexisting with Pb. The Cu-Ca coprecipitate could enhance the stability of Cu in dilute acid solution and soil with or without a plant, whiles the Cu-Pb one showed the opposite effect. Also, the Cu-induced phosphate precipitates were relatively stable and not easy to be absorbed by Pakchoi (Brassica rapa var. chinensis). The results showed that the influence of coexisting metal ions should be considered when phosphate mineralisation technology is used to immobilise heavy metals in the environment.

Comparison of sorption efficiency of natural and MnO2 coated zeolite for copper removal from model solutions

Removal of heavy metals from the environment is important for living beings. The present work investigates the applicability of the natural and MnO2 - coated zeolite as sorbent for the removal of copper from synthetic solutions. Batch experiments were carried out to identify the influence of initial pH and concentration in the process of adsorption. A maximum removal efficiency of Cu(II) was observed in 10 mg/L for natural (95.6%) and modified (96.4%) zeolite, where the values was almost identical, but at concentration of 500 mg/L was the removal efficiency of modified zeolite three times higher. Based on the correlation factors R2, the Langmuir isotherms better describe the decontamination process than Freundlich. The optimum pH value was set at 5.0.

Efficiency assessment of ZVI-based media as fillers in permeable reactive barrier for multiple heavy metal-contaminated groundwater remediation

Four zero valent iron-based composites were prepared and applied as the reactive media of permeable reactive barriers. Batch tests and continuous-flow column experiments were conducted to assess the long-term performance of these composites for possible utilization as fillers for PRB. The experimental results of the batch tests revealed that in single-metal systems, the removal efficiency of Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) could reach 98% at equilibrium. Equilibrium data showed that composites displayed different selectivity values in binary and quaternary-component systems. For the continuous tests, column filled with chitosan-zero valent iron-based composites, exhibited optimal removal efficiency and achieved average removal values of 98.84%, 88.28%, 95.65% and 87.10% for Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) during the whole 30-day operation, respectively. Dynamic removal improvement of multiple metals was observed with further assembly media, with average removal of 99.11%, 90.05% and 87.34% for Cu(Ⅱ), Co(Ⅱ) and As(Ⅲ), respectively. Combined with superficial characteristic analysis, the functional groups distributed on the surface of composites played a key role in metal sorption. Moreover, the adsorbed Cu(Ⅱ), Co(Ⅱ) and Cr(Ⅵ) gradually transferred to the mobile phase when the operational periods were prolonged, while As(Ⅲ) became more stable.

Highly Efficient Removal of Cu(II) Ions from Acidic Aqueous Solution Using ZnO Nanoparticles as Nano-Adsorbents

Water pollution by heavy metals has significant effects on aquatic ecosystems. Copper is one of the heavy metals that can cause environmental pollution and toxic effects in natural waters. This encourages the development of better technological alternatives for the removal of this pollutant. This work explores the application of ZnO nanoparticles (ZnO-NPs) for the removal of Cu(II) ions from acidic waters. ZnO NPs were characterized and adsorption experiments were performed under different acidic pHs to evaluate the removal of Cu(II) ions with ZnO NPs. The ZnO NPs were chemically stable under acidic conditions. The adsorption capacity of ZnO NPs for Cu(II) was up to 47.5 and 40.2 mg·g−1 at pH 4.8 and pH 4.0, respectively. The results revealed that qmax (47.5 mg·g−1) and maximum removal efficiency of Cu(II) (98.4%) are achieved at pH = 4.8. In addition, the surface roughness of ZnO NPs decreases approximately 70% after adsorption of Cu(II) at pH 4. The Cu(II) adsorption behavior was more adequately explained by Temkin isotherm model. Additionally, adsorption kinetics were efficiently explained with the pseudo-second-order kinetic model. These results show that ZnO NPs can be an efficient alternative for the removal of Cu(II) from acidic waters and the adsorption process was more efficient under pH = 4.8. This study provides new information about the potential application of ZnO NPs as an effective adsorbent for the remediation and treatment of acidic waters contaminated with Cu(II).

Novel disinfection method for toxic cyanobacteria (Oscillatoria tenuis) and simultaneous removal of cyanotoxins aided by recyclable magnetic nanoparticles

An optimized disinfection method with metal ions to address cyanobacteria contamination in freshwater is presented, based on recyclable magnetic nanoparticles. In this study, the disinfection ability of individual metal ions (Ag+ and Cu2+) and combined (Ag+ + Cu2+) were evaluated with a target cyanobacteria, Oscillatoria tenuis, under various environmental conditions. The usage of combined Ag+ and Cu2+ reduces the time and concentration needed to achieve the same disinfection effectiveness compared to individual metal ions. However, the addition of Cu2+ and Ag+ stimulated production of cyanotoxin during disinfection, with an increase of 24.8% for anatoxin-a. To reduce the potential health risk, we evaluated the recovery and reuse of metal ions, and removal of cyanotoxins after disinfection, using magnetic nanoparticles with permanently confined micelle arrays (Mag-PCMA) under various environmental conditions. Recovery efficiency of Ag+, the most valuable ion, was excellent (99.8%), although it decreased to 74.5% with increasing Cl- concentration (0–10 mg/L). The regeneration and reuse of Mag-PCMA was studied for 5 cycles. Removal efficiency of Cu2+, anatoxin-a and cylindrospermopsin were minimally changed during the 5 sorption-desorption cycles, and that of Ag+ remained above 93% by the end of 5th cycle, indicating that this disinfection method may be sustainable for practical use with low energy requirements and minimized environmental impacts.

Chelating surfactant N-lauroyl ethylenediamine triacetate enhanced electrokinetic remediation of copper and decabromodiphenyl ether co-contaminated low permeability soil: Applicability analysis

In this study, chelating surfactant N-lauroyl ethylenediamine triacetate (N-LED3A) was used as strengthening agent for electrokinetic (EK) remediation of copper (Cu) and decabromodiphenyl ether (BDE209) co-contaminated low permeability soil. The results indicated that negligible amount of N-LED3A would be adsorbed on the experimental soil. The synchronous elution efficiencies (SEEs) of Cu and BDE209 had reached 65.4% and 49.9%, respectively, when the concentration of N-LED3A was 4000 mg/L, and they kept almost unchanged as the concentration of N-LED3A further increased. Meanwhile, the optimal SEEs were obtained at the pH condition within 6–8. The removal efficiencies of Cu (55.3%–65.8%) and BDE209 (31.4%–46.4%) would be increased with the applied voltage gradient and concentration of N-LED3A. In addition, BDE209 and Cu contaminants were also detected in the catholyte and anolyte, respectively, and their concentrations still showed an uptrend by the end of the experiments. While in the control experiments, the removal efficiency of Cu was in the range of 18.2%–23.6%, and almost no BDE209 was migrated out. The electric current would be increased with N-LED3A concentration increased, further resulting in the enhancement of cumulative electro-osmotic flow (EOF). However, the increment of EOF was limited after an 8-day treatment due to the declined capacity of the soil water supply, and the removal efficiency of BDE209 did not change proportionally to the cumulative EOF as a consequence. The accumulated (21 days) energy consumption under the optimal operation conditions (voltage gradient 1 V/cm, N-LED3A 1 g/L) was 377.28 KWh/m3. Efficiently synchronous removal of BDE209 and Cu could be achieved by the N-LED3A enhanced EK technique, exhibiting a promising application potential in the organic pollutant and heavy metal co-contaminated soil remediation.