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In this research work, surface-modified nano zerovalent copper (nZVC) was prepared using a simple borohydride reduction method. The spectroscopic and crystallographic results revealed the successful synthesis of surface-modified nano zerovalent copper (nZVC) using solvents such as ethanol (ETOH), ethylene glycol (EG) and tween80 (T80). The as-synthesized material was fully characterized for morphological surface and crystal structural properties. The results indicated that EG provides an excellent synthesis environment to nZVC compared to ETOH and T80 in terms of good dispersion, high surface area and excellent catalytic properties. The catalytic efficiency of nZVC/EG was investigated alone and with peroxymonosulphate (PMS) in the absence of light. The degradation results demonstrated that the involvement of PMS synergistically boosted the catalytic efficiency of synthesized nZVC/EG material. Furthermore, the degradation products (DPs) of CBZ were determined by GC−MS and subsequently, the degradation pathways were proposed. The ecotoxicity analysis of the DPs was also explored. The proposed (nZVC/EG/PMS) system is economical and efficient and thus could be applied for the degradation of CBZ from an aquatic system after altering the degradation pathways in such a way that results in harmless products. [ABSTRACT FROM AUTHOR]

Chromium (Cr), due to its greater contamination in aquifers and distinct eco-toxic impacts, is of greater environmental concern. This study aimed to synthesize nanocomposites of almond shells biochar (BC) with zerovalent bismuth and/or copper (Bi0/BC, Cu0/BC, and Bi0–Cu0/BC) for the removal of Cr from aqueous solution. The synthesized nanocomposites were investigated using various characterization techniques such as XRD, FTIR spectroscopy, SEM, and EDX. The Cr removal potential by the nanocomposites was explored under different Cr concentrations (25–100 mg/L), adsorbent doses (0.5–2.0 g/L), solution pH (2–8), and contact time (10–160 min). The above-mentioned advanced techniques verified successful formation of Bi0/Cu0 and their composite with BC. The synthesized nanocomposites were highly effective in the removal of Cr. The Bi0–Cu0/BC nano-biocomposites showed higher Cr removal efficiency (92%) compared to Cu0/BC (85%), Bi0/BC (76%), and BC (67%). The prepared nanocomposites led to effective Cr removal at lower Cr concentrations (25 mg/L) and acidic pH (4.0). The Cr solubility changes with pH, resulting in different degrees of Cr removal by Bi0–Cu0/BC, with Cr(VI) being more soluble and easier to adsorb at low pH levels and Cr(III) being less soluble and more difficult to adsorb at high pH levels. The experimental Cr adsorption well fitted with the Freundlich adsorption isotherm model (R2 > 0.99) and pseudo-second-order kinetic model. Among the prepared nanocomposites, the Bi0–Cu0/BC showed greater stability and reusability. It was established that the as-synthesized Bi0–Cu0/BC nano-biocomposite showed excellent adsorption potential for practical Cr removal from contaminated water. [ABSTRACT FROM AUTHOR]

Batch scale removal of arsenic (As) from aqueous media was explored using nano-zero valent iron (Fe0) and copper (Cu0) particles. The synthesized particles were characterized using a Brunauer-Emmett–Teller (BET) surface area analyzer, a scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The BET result showed that the surface area (31.5 m2/g) and pore volume (0.0415 cm3/g) of synthesized Fe0 were higher than the surface area (17.56 m2/g) and pore volume (0.0287 cm3/g) of Cu0. The SEM results showed that the morphology of the Fe0 and Cu0 was flowery microspheres and highly agglomerated with thin flakes. The FTIR spectra for Fe0 showed broad and intense peaks as compared to Cu0. The effects of the adsorbent dose (1–4 g/L), initial concentration of As (2 mg/L to 10 mg/L) and solution pH (2–12) were evaluated on the removal of As. Results revealed that effective removal of As was obtained at pH 4 with Fe0 (94.95%) and Cu0 (74.86%). When the dosage increased from 1 to 4 g L−1, the As removal increased from 70.59 to 93.02% with Fe0 and from 67 to 70.59% with Cu0. However, increasing the initial As concentration decreased the As removal significantly. Health risk indices, including estimated daily intake (EDI), hazard quotient (HQ), and cancer risk (CR) were employed and a significant decline (up to 99%) in risk indices was observed in As-treated water using Fe0/Cu0. Among the adsorption isotherm models, the values of R2 showed that isothermal As adsorption by Fe0 and Cu0 was well explained by the Freundlich adsorption isotherm model (R2 > 0.98) while the kinetic experimental data was well-fitted with the Pseudo second order model. The Fe0 showed excellent stability and reusability over five sorption cycles, and it was concluded that, compared to the Cu0, the Fe0 could be a promising technology for remediating As-contaminated groundwater. [ABSTRACT FROM AUTHOR]

This study focuses on investigating and comparing the influence of the surface functional groups and chemical matrices of macroporous resin on the Cr(III) exchange mechanism. The results discussed herein indicate that sulfonic resin removed Cr(III) ions with faster kinetics than carboxylic resin. Equilibrium was established within 15 and 7 min for the carboxylic and sulfonic resins, respectively, with a 99.5% removal efficiency at 333 K. The Langmuir exchange capacity was observed to be higher for the sulfonic resin (1.5 mmol∙g−1) than the carboxylic resin (0.80 mmol∙g−1) at 333 K. The adsorption isotherms obtained for the carboxylic and sulfonic resins were H and S types, respectively, representing a higher affinity of the carboxylic resin for Cr(III) removal at a low metal ion concentration. Additionally, it was noted that the carboxylic resin preferentially co-sorbed H+ and Cr(OH)2+ ions below Cr(III) concentrations of 6–8 mmol.L−1. The H+ ions co-sorption was almost negligible, whereas the Cr(III) exchange was 87 and 34.5% for the carboxylic acid resin and sulfonic acid resins, respectively. The data of the concentration studies were evaluated using non-linear forms of Freundlich, Langmuir, and Dubinin–Radushkevich adsorption isotherm models, and the kinetic data were analyzed using pseudo-Ist- and pseudo-IIst-order kinetic models. The activation energy Ea for Amberlite IRC-50 (Na+) was greater (22.4 kJ∙mol−1) than that of Amberlyst-15 (Na+) 17 kJ∙mol−1, indicating a higher energy barrier for the ion exchange reaction on carboxylic resin. As per the findings of a statistical error analysis (RMSE and SSE) and absolute average relative distribution (AARD) statistical model, a close agreement between the experimental and theoretical values suggested that the Langmuir isotherm was well-fitted to the current adsorptive investigations. The interaction of the COO− and SO3− functional sites of the resins for the exchange of Cr(III) ions was validated through an FT-IR analysis. The macroporous resins used in the current study for Cr(III) exchange showed promising performances compared to other resins. The current investigations revealed valuable insights for choosing macroporous resins as adsorbents in water filtration systems. [ABSTRACT FROM AUTHOR]

In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe3O4) is employed as an adsorbent to remove phosphate ions (PO43−) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe3O4 nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe3O4 demonstrated the adsorbent's granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe3O4 showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe3O4 adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO43− ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe3O4 towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability. [ABSTRACT FROM AUTHOR]

In this study, biochar was prepared from Sidr plant leaves and used for the treatment of ciprofloxacin (CIP)-contaminated water. CIP is important class of emerging water pollutants from pharmaceutical industries. The biochar showed 65% adsorption efficiency and 43.48 mg/g adsorption capacity of CIP. Adsorption efficiency as well as adsorption capacity were improved to 91% and 62.50 mg/g, respectively, by phosphoric acid (H3PO4) modified biochar. Removal of CIP by the prepared biochar was due to different surface functional groups of CIP and biochar as revealed from the study of different characterization analyses. The presence of PO43– group in modified biochar led to maximum binding of CIP. Also, the modified biochar showed higher reusability potential and less leaching of ions when compared to the raw biochar. Removal of CIP was affected by concentrations of CIP, the amount of biochar and different pH's; the maximum removal of CIP was achieved at pH 4. The Freundlich and pseudo-first-order models best fitted the removal of CIP by modified biochar. Advanced characterization techniques were applied to investigate surface and physiological characteristics of the biochar and modified biochar. The modification showed high impact on the performance and stability of biochar. The study showed significant impacts of modification on the potential of the biochar for treatment of CIP-contaminated water. [ABSTRACT FROM AUTHOR]

Binary composite of zerovalent iron and titanium dioxide (Fe0/TiO2) was synthesized for the catalytic removal of dichlorophene (DCP) in the presence of peroxymonosulfate (PMS). The as-prepared composite (Fe0/TiO2) exhibits synergistic effect and enhanced properties like improved catalytic activity of catalyst and greater magnetic property for facile recycling of catalyst. The results showed that without addition of PMS at reaction time of 50 min, the percent degradation of DCP by TiO2, Fe0, and Fe0/TiO2 was just 5%, 11%, and 12%, respectively. However, with the addition of 0.8 mM PMS, at 10 min of reaction time, the catalytic degradation performance of Fe0, TiO2, and Fe0/TiO2 was significantly improved to 82%, 18%, and 88%, respectively. The as-prepared catalyst was fully characterized to evaluate its structure, chemical states, and morphology. Scanning electron microscopy results showed that in composite TiO2 causes dispersion of agglomerated iron particles which enhances porosity and surface area of the composites and X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FTIR) results revealed successful incorporation of Fe0, and oxides of Fe and TiO2 in the composite. The adsorption–desorption analysis verifies that the surface area of Fe0/TiO2 is significantly larger than bare Fe0 and TiO2. Moreover, the surface area, particle size, and crystal size of Fe0/TiO2 was surface area = 85 m2 g−1, particle size = 0.35 μm, and crystal size = 0.16 nm as compared to TiO2 alone (surface area = 22 m2 g−1, particle size = 4.25 μm, and crystal size = 25.4 nm) and Fe0 alone (surface area = 65 m2 g−1, particle size = 0.9 μm, and crystal size = 7.87 nm). The as-synthesized material showed excellent degradation performance in synthesized wastewater as well. The degradation products and their toxicities were evaluated and the resulted degradation mechanism was proposed accordingly. The toxicity values decreased in order of DP1 > DP5 > DP2 > DP3 > DP4 and the LC50 values toward fish for 96-h duration decreased from 0.531 to 67.2. This suggests that the proposed technology is an excellent option for the treatment of antibiotic containing wastewater. [ABSTRACT FROM AUTHOR]

In this study, a stable ionic liquid (IL) mediated zero‐valent copper nanoparticle (nZVCu), namely IL‐nZVCu, has been evaluated for catalytic properties towards H2O2‐mediated TMB (3, 3',5,5'‐tetramethylbenzidine) reaction under normal conditions of temperature and pH. The various analytical techniques like Fourier Transform Infrared Spectroscopy (FT‐IR), UV–Vis diffuse reflectance spectroscopy (UV‐Vis DRS), X‐ray powder diffraction (XRD), scanning electron microscope (SEM), Transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS) were used to confirm the structure and nano size of nZVCu. The simple protic IL 1‐hydrogen‐3‐methylimidazolium acetate (HmimOAc) with its cation 1‐methylimidazole and anion acetate was synthesized, characterized, and coated on nZVCu to prepared IL‐nZVCu. As a novel mimic peroxidase, IL‐nZVCu could quickly catalyze the oxidation reaction of specific chromogenic substrate TMB, when H2O2 acts as an oxidant, followed by a remarkable color change in the solution measured by UV/Vis Spectrophotometry. The enhanced catalytic activity and significant color change were greatly dependent on the catalyst dosage, the volume of IL taken, incubation time, H2O2 concentration, and TMB concentration. Also, IL‐nZVCu showed no response toward ascorbic acid, cholesterol, dopamine, urea and uric acid. Based on these findings, IL‐nZVCu could be effectively used for visual colorimetric sensing of H2O2 with a limit of detection (LOD) of 44 μM over the dynamic linear range from 40 μM to 1000 μM concentration. [ABSTRACT FROM AUTHOR]

Abstract Removal of cadmium (Cd2+), a highly toxic heavy metal, from aqueous solutions was investigated using nano zerovalent iron (Fe0). Cadmium was efficiently removed by Fe0, although reactivity and reusability of Fe0 was significantly promoted by coupling with bismuth (Bi). At a reaction time of 20 min, 85% and 96% Cd2+ was removed by Fe0 and Bi/Fe0, respectively, at first cycle using [Cd2+] 0 = 10 mg/L and [Fe0] 0 = [Bi/Fe0] 0 = 1.0 g/L. However, Cd2+ removal efficiency was reduced to 12% and 80% at sixth cycle by Fe0 and Bi/Fe0, respectively. The X-Ray diffraction and energy dispersive X-Ray spectroscopy analysis proved successful formation of Fe0 by the chemical reduction method and also confirmed coupling of Bi with Fe0 to form bimetallic Bi/Fe0. The oxidation of Fe0 and Bi/Fe0 yielded electron that played significant role in the conversion of toxic Cd2+ into non-toxic Cd0. The reactivity of electron with Cd2+ was calculated to be 4.3 × 109 M−1 s−1. The pH of solution showed pronounced effects on the reactivity of both Fe0 and Bi/Fe0. Removal of Cd2+ by both Fe0 and Bi/Fe0 followed pseudo-first-order kinetic model. The conversion of Cd2+ into non-toxic Cd0 proved Fe0 and Bi/Fe0 to be highly efficient and rewarding in detoxification of Cd2+ and other toxic metals in aqueous environments. Graphical abstract Unlabelled Image Highlights • Bi was successfully coupled with Fe0 using chemical reduction method. • The Bi coupled Fe0 displayed greater reactivity, stability, and reusability. • Second-order rate constant of hydrated electron with Cd2+ was estimated. • pH of aqueous solution significantly influenced efficiency of Fe0 and Bi/Fe0. [ABSTRACT FROM AUTHOR]

This paper comprises a comprehensive kinetic study for the adsorptive removal of As (V) from aqueous medium by mixed oxide (MO) of iron and silicon. The multi-linearity of the intraparticle diffusion model pointed towards the likelihood of both the pore and film diffusion. The Boyd model validated film diffusion to be the principal mechanism responsible for controlling the rate of the arsenate adsorption on MO. The negative entropy of activation (ΔS#) suggested the adsorption mechanism to be associative in nature. The non-negative values of ΔG# suggested the presence of an energy barrier to be surmounted for the reaction to occur. [ABSTRACT FROM AUTHOR]