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This work reports the results of coupling Moringa oleifera seed extract (MOSE) with electrocoagulation (EC) for the remediation of Direct Red 80 azo dye (DR80) from contaminated synthetic aqueous solution and real textile wastewater. The electrochemical treatment was carried out using a pair of aluminium electrodes in monopolar-parallel mode. EC runs determined using Box-Behnken design under the response surface methodology (RSM) for three parameters including current density, pH, and operation time. The EC optimal conditions were current density 0.9 mA/cm2, pH 3, and time 10 min. The maximum experimental DR80 dye removal of 89.37% was close to the model prediction (76.4%). The kinetic study of the EC system represented that the removal of dye obeyed the first-order kinetic model. To improve dye removal efficiency from treated wastewater under optimal conditions, 2.5 mL/L of MOSE was added and the efficiency enhanced to above 98%. SEM and microscopic images of the sludge produced showed that the flocs formed in the hybrid system were denser and thicker than the conventional EC. The economic study revealed that switching from the EC to hybrid process reduced energy and electrode consumption from 0.015 to 0.008 kWh/m3 and 0.016 to 0.014 kg/m3, respectively, for 98% DR80 dye removal. MOSE has a substantial effect on the EC performance. Therefore, the EC/MOSE coupling process is recommended for the treatment of coloured wastewater due to its high efficiency, short operation time, and electrode and energy consumption costs. [ABSTRACT FROM AUTHOR]

The aim of the present study was to prepare the modified magnetic activated carbon from sawdust (AC/Fe3O4@SiO2-APTMS) as a novel adsorbent for efficient removal of humic acid (HA) from aqueous solutions. The adsorbent was characterised by BET, SEM, FTIR, VSM, and EDS analysis. The optimal values of independent variables were determined using Box-Behnken design based on the response surface methodology (RSM). The maximum HA adsorption of 97.85% was obtained at optimal conditions pH 3, the adsorbent dose 2 g/L, and the contact time 25 min. Analysis of the adsorption data by isothermal, kinetic, and thermodynamic models showed that the adsorption data followed the Langmuir isotherm (R2 = 0.9850) and the pseudo-second-order kinetic model (R2 = 0.9999). The adsorption process was spontaneous and endothermic. The adsorbent regeneration proved high HA removal efficiency after 4 adsorption cycles. The humic acid adsorption behaviour of the adsorbent supports its performance to remove organic contaminants from aqueous solutions. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigation of processes for Pb2+ elimination from water/wastewater as a significant public health issue in many parts of world. The removal of Pb2+ ions by various nanocomposites has been explained from water/wastewaters. ZnO-based nanocomposites, as eco-friendly nanoparticles with unique physicochemical properties, have received increased attention to remove Pb2+ ions from water/wastewaters. Design/methodology/approach: In this review, different ZnO-based nanocomposites were reviewed for their application in the removal of Pb2+ ions from the aqueous solution, typically for wastewater treatment using methodology, such as adsorption. This review focused on the ZnO-based nanocomposites for removing Pb2+ ions from water and wastewaters systems. Findings: The ZnO-based nanocomposite was prepared by different methods, such as electrospinning, hydrothermal/alkali hydrothermal, direct precipitation and polymerization. Depending on the preparation method, various types of ZnO-based nanocomposites like ZnO-metal (Cu/ZnO, ZnO/ZnS, ZnO/Fe), ZnO-nonmetal (PVA/ZnO, Talc/ZnO) and ZnO-metal/nonmetal (ZnO/Na-Y zeolite) were obtained with different morphologies. The effects of operational parameters and adsorption mechanisms were discussed in the review. Research limitations/implications: The findings may be greatly useful in the application of the ZnO-based nanocomposite in the fields of organic and inorganic pollutants adsorption. Practical implications: The present study is novel, because it investigated the morphological and structural properties of the synthesized ZnO-based nanocomposite using different methods and studied the capability of green-synthesized ZnO-based nanocomposite to remove Pb2+ ions as water contaminants. Social implications: The current review can be used for the development of environmental pollution control measures. Originality/value: This paper reviews the rapidly developing field of nanocomposite technology. [ABSTRACT FROM AUTHOR]

The objective of this study was to use activated carbon produced from poplar sawdust (ACPSD) as an adsorbent to remove Reactive Black 5 dye from aqueous solution. Investigation of the properties of the prepared activated carbon by scanning electron microscopy showed that it has a porous structure. Adsorption experiments were carried out according to the Box–Behnken design and base on response surface methodology (RSM) under different operational parameters including pH, initial dye concentration, adsorbent dose, and contact time. The maximum dye removal of 80.19% was obtained under optimum conditions pH 3, dye concentration 4 mg/L, contact time 109 min, and the adsorbent dose 4 g/L. The maximum experimental dye removal was close to the predicted value of 78.32% which confirms the suitability of the selected statistical model. The findings showed the data were fitted well with the pseudo-second-order kinetic model (R2 = 0.992), and the equilibrium data were in agreement with the Langmuir isotherm (R2 = 0.999). In the thermodynamic studies of the adsorption process, negative value ΔG and positive value of ΔH showed that the process was spontaneous and endothermic. Also based on the results of the regeneration process, the ACPSD as an efficient adsorbent could be used for four adsorption cycles with high dye removal efficiency. [ABSTRACT FROM AUTHOR]

In addition to the large volume, the generated wastewater in paper and cardboard recycling industry contains various organic compounds and dyes. Treatment of these wastewaters is difficult due to the diversity of contaminants and the complexity of their chemical structure. This study aimed to investigate the efficiency of the coagulation and flocculation process by the new mixture of coagulants for wastewater treatment in one of the paper and cardboard recycling industries. To determine the efficiency of the coagulation and flocculation process in removing the parameters, including turbidity, colour, TSS, and COD, the Jar Test was used in laboratory conditions. By changing the variables, such as pH, coagulant type (PAC/MgCl2, PAC/Polymer, MgCl2/Polymer, MgCl2/PAC, PAC/MgCl2/Polymer), coagulant dose, and polymer dose, the optimal conditions were determined. Based on the results, the highest turbidity removal efficiency was achieved for the combination of coagulant and coagulant aid (PAC/MgCl2/Polymer) at pH 11. According to the experiments, the highest removal efficiency of turbidity, colour, COD and TSS were95.43%, 25.16%, 16.16%, and 83.33%, respectively. According to the obtained results, the coagulation and flocculation is a suitable method to remove turbidity and suspended solids in the paper and cardboard recycling industry wastewater. However, in order to remove more colour and COD, additional treatment is required. [ABSTRACT FROM AUTHOR]

Natural organic materials, principally humic acids cause serious problems in water treatment plants due to combination with chlorine and the formation of carcinogenic disinfection by-products. In the present study, the Fe3O4@L-arginine magnetic nanoparticle was synthesised and used to adsorbhumic acid (HA) from the aqueous solution. Fe3O4@L-arginine nanoparticles were prepared withthe co-precipitation method and characterised by FE-SEM, FTIR, XRD, and zeta potential analysis. The effect of different parameters on the HA removal by Fe3O4@L-arginine was investigated. The results showed that by increasing the adsorbent dose, contact time and temperature, the efficiency of HA removal increased, but by increasing theinitial concentration of HA, ionic strength, and pH, the efficiency of HA elimination decreased. Under optimal conditions, the highest HA removal efficiency in 0.5 g/L and 2 g/L adsorbent doses was found to be 67.23% and 96.4%, respectively. Also, the study of isotherm and kinetic of adsorption showed that the adsorption of HA on Fe3O4@L-arginine followed Langmuir isotherm and pseudo-second-order kinetic.Adsorption experiments demonstrated that Fe3O4@L-arginine as an effective and reusable adsorbent has a good capacity for the removal of HA from aqueous solution. [ABSTRACT FROM AUTHOR]

In the present study, the efficiency of amine-functioned Fe3O4 magnetic nanoparticles with L-arginine (Fe3O4@L-arginine) for the removal of RB5 azo dye from aqueous solution was investigated. Box–Behnken design was used to design the experiments and optimise the adsorption parameters. The results showed that Fe3O4@L-arginine nanoparticles were synthesised successfully. Optimum conditions for dye adsorption were obtained at a dye concentration of 50 mg/L, adsorbent dose of 0.8 g/L and pH 3 with an efficiency of 97.6% that was close to the model's prediction percentage (96.8%), which confirms the validity of the model. The RB5 dye adsorption followed the pseudo-second-order kinetic model and the Temkin isotherm model, and the adsorption was a spontaneous endothermic process. The results illustrated that the Fe3O4@L-arginine nanoparticles can be used for RB5 dye adsorption by maintaining high efficiency for several times. Therefore, Fe3O4@L-arginine nanoparticles because of their high performance, easy synthesis and use and ease of separation are suitable adsorbents to remove dye from the coloured wastewater. [ABSTRACT FROM AUTHOR]

While chlorination is critical for water disinfection, a knowledge gap includes the nature of free residual chlorine (FRC) decay, which was investigated using four physical methods (SSA, SSR with and without a lid, heating, and incubator shaker). Keeping water samples in SSA and SSR methods for 24 h resulted in the FRC decline by 62% and 51%, respectively. The heterotrophic plate count (HPC) increased significantly between initial (3.17 ± 2.6–3.82 ± 1.1 CFU/mL) and final samples (6.7 ± 1.5–94.7 ± 4.72 CFU/mL) for both SSA and SSR methods. Thermodynamic behavior (ΔH versus ΔG) of FRC decay of the different methods was characterized. [ABSTRACT FROM AUTHOR]

In this work, the optimum condition for the adsorption of Reactive Blue 19 dye onto Fe3O4 functionalized with hyperbranched polyethylenimine (Fe@HPEI) was determined using response surface methodology. The properties of synthesized magnetic Fe@HPEI nanoparticles were ascertained using FTIR, SEM, TEM, VSM and zeta potential measurement. The experimental adsorption data indicating the positive effect of adsorbent dose and contact time, and the negative effect of pH, initial dye concentration and ionic strength on dye adsorption. At optimal condition; pH 3.4, contact time 25 min, adsorbent dose 0.4 g/L and initial dye concentration 113 mg/L, Fe@HPEI nanoparticles removed dye up to 99.27%. The maximum experimental dye adsorption was near to the predicted value of 100%, which confirmed the reliability of the selected statistical model. The dye adsorption data were fitted well to Langmuir isotherm and pseudo-second-order kinetic, and the maximum adsorption capacity was 500 mg/g. Totally, Fe@HPEI as an effective superadsorbent can be repeatedly utilized for the adsorption of dye from the aqueous environment. [ABSTRACT FROM AUTHOR]

The entry of toxic organic pollutants and resistant to biodegradation has increased the concern about human health. The use of advanced oxidation (AO) processes to degrade these pollutants has been developing. One of the AO processes is based on the use of hydrogen peroxide in removing resistant organic pollutants. This study aimed to develop a new reactor capable of producing H 2 O 2 in the solution. Therefore, a porous electrode made of stainless steel with the capability of air injection in the electrode center was used. The 30 cm rod graphite electrodes were also used as an anode electrode in a 4000 ml reactor. The effects of variables, including current density (30-40 mA/cm 2 ), time (10-30 min), and electrolyte concentration (12-17 mM/L) on the amount of H 2 O 2 production were evaluated by Box behenken design under response surface methodology using Design expert software. The results of this study showed that H 2 O 2 can be produced at the electrode surface of porous cathode under optimal conditions of 36 mA/cm 2 current density, 16 mM/l electrolyte concentration, in 23 min, and in the amount of 34 ppm. Using a porous cathode electrode causes the maximum contact among the solution, water, and air, and increases the production of H 2 O 2 . The release of resistant organic compounds to the waste water is a serious problem to the environment. By the application of the Electro-oxidation (EO)reactor with the ability to produce H 2 O 2 , this issue is resolved. Furthermore, this technique is applied for non-selective degradation of the toxic organic compounds. •The electro-oxidation process is a useful method for destruction of persistent organic matter from wastewater.•Due to use of porous cathode in this method, contact between the electrode and the sewage is at its maximum level which increases the efficiency and speed of sewage treatment.•This method can produce H 2 O 2 as a high potential oxidant that can reduce persistent organic properties of sewage and make the wastewater suitable for biological treatment.