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The discharge of untreated electroplating wastewater could lead to the formation of toxic metal-organic complexes that is harmful for the environment. There are several processes reported to treat electroplating wastewater such as chemical precipitation, adsorption, coagulation and flocculation, ion exchange, electrocoagulation, membrane filtration, advanced oxidation process and biorecovery. These methods provide the possibility to capture different toxic metals and remove organic pollutants. The combination of different processes together has shown higher efficiencies in removing a wide range of contaminants than single treatment systems. The main challenge is identifying the highest treatment performance and most cost-efficient process. This review provides an overview of treatment technologies for electroplating wastewater and describes the strengths and drawbacks among them. The efficiency of different systems and kinds of pollutants removed, along with a comparison between these systems have been analysed. When comparing the treatment technologies, it is hard to identify the most efficient one as each method has been successful in removing certain pollutants that has not been recovered from the other methods. Therefore, making the decision on identifying the best treatment technology depends on the objective of the treatment and the targeted pollutants. Furthermore, the cost of different technologies has been evaluated based on literature to have a brief look at cost differences between the technologies. When targeting removal of heavy metals, the highest cost of treatment has been reported at around 4.45 $/m3 for the adsorption method employing nano zero valent iron (nZVI). While the lowest cost of treatment has been reported at about 0.35 USD/m3 employing an adsorption method followed by electrodeposition. [ABSTRACT FROM AUTHOR]

Methylene blue (MB) is a heterocyclic aromatic dye that is difficult to biodegrade due to its complex chemical structure. In this study, chemically prepared nano zero-valent aluminum (nZVAl) was investigated for the first time for one-step removal of MB from aqueous solutions under different experimental factors (pH, dosage, time, MB concentration, stirring rate, temperature, detergents, and ionic strength). The prepared nZVAl material was characterized using XRD, TEM, SEM, EDS, and FTIR. Results indicated that at an initial MB concentration of 10 mg/L, pH 10, nZVAl dosage 1.0 g/L, stirring rate 200 rpm, and temperature 30 °C, the removal efficiency of approximately 99.0% was achieved within an equilibrium time of 90 min. An improvement in MB removal efficiency was observed in the presence of inorganic salts, while the presence of detergents resulted in a reduction in MB removal efficiency. The isotherm adsorption data were best fitted by the Freundlich isotherm model (R2: 0.9569), while the kinetic data were well described by the pseudo-second-order (PSO) model (R2: 0.9999). Based on the thermodynamic study, the MB adsorption process is physically diffusion-controlled. The adsorption of MB onto nZVAl was accurately described using an artificial neural network (ANN) with a structure of 11–10–1 and R2 of 0.97. The overall cost of scaling up the adsorption unit to be used for MB removal from aqueous solutions under the optimum conditions is about US$1.31/m3. Consequently, this study opens the door for other researchers to test nZVAl in treating real textile wastewater. [ABSTRACT FROM AUTHOR]

This study investigated the adsorption of PO43− onto encapsulated nanoscale zero-valent iron (nZVI). At initial PO43-: 10 mg · L−1, the optimum condition was initial pH: 6.5, nZVI dosage: 20 g · L−1, stirring-rate: 100 rpm, and time: 30 min, achieving PO43− removal of 42%. The effect of pH and time on the PO43− removal efficiency was quadratic-linear concave up, whereas the curve of nZVI dosage was quadratic-convex. Artificial neural network with a structure of 5−7−1 adequately predicted PO43− removal (R2: 97.6%), and the sensitivity analysis demonstrated that pH was the most influential input. The cost of the adsorption unit was 3.15 $USD · m−3. [ABSTRACT FROM AUTHOR]