Electrokinetic removals of arsenate and arsenite from the aqueous environment by a fluidized bed of superparamagnetic iron oxide nanoparticle-coated pyrite microelectrodes

ABSTRACT

Superparamagnetic iron oxide nanoparticle-coated pyrite microelectrodes were synthesized and applied for the arsenic removal from the binary system in a three-dimensional fluidized reactor. Arsenate adsorption was highly dependent on the environmental pH values. The maximum monolayer adsorption capacities were 12.83 mg/g and 9.28 mg/g for As(V) and As(III), respectively. The direct contact between nucleus and target contaminants evidently affected As(III) equilibrium adsorption. Voltage gradient had a more remarkable influence on the arsenic removal compared with the other parameters in the optimization. A continuous flow was recommended in the industrial application based on the regeneration and reuse of adsorbent.

KEYWORDS:

• Arsenic
• superparamagnetic iron oxide nanoparticle-coated pyrite
• electrokinetic removal
• three-dimensional electrode
• enhancement

Novelty Statement

Techniques available for remediating arsenic-contaminated water mainly include chemical precipitation, physiochemical adsorption, ion exchange, and membrane separation, etc. The adsorption process is more broadly adopt for the removal of contaminants in the aqueous environment due to its effective cost and operational simplicity. Adsorbent materials including activated carbon, (hydro)oxides of metals, ion exchange resin, and clay minerals, etc., have been chosen to remove arsenate and arsenite in different pH environments. However, the presence of some competing ions in the real environment perplexes the preferential adsorption and limits the further separation application of materials. The main objective of this research is to investigate the invigoration effect of 3D EK process on the arsenic removals from the stock solutions using the superparamagnetic iron oxide nanoparticles (SPIONs)-coated pyrite particles. The SPIONs-coated pyrite adsorbent was synthesized by a hydrometallurgical method in a short time. The effects of variables including the initial pH, adsorbent dosage, voltage gradient, proposing time, temperature and stirring rate on the arsenic adsorption in the equilibrium tests and 3D electrochemical systems were comprehensively studied and analyzed to optimize the combination of the external parameters and achieve the electrokinetic enhancement on the arsenic adsorption at the aqueous environments. The adsorption kinetics and isotherms in the binary systems were researched in depth based on the results from the equilibrium adsorption experiments to make more detailed the adsorption pathways of As(V) and As(III) from the free form to the binding state. The real environment was simulated by drawing the inorganic oxyanions into the stock solution to expound the interference of the competitive ions on the arsenic removal and elucidate the impact electric field on the interfering abatement. Finally, the repeatability of adsorbent in the EK process was evaluated to further maximize the running efficiency of the system and minimize the operational costs. This study is to contribute to demonstrate the feasibility of enhancing the arsenic removal through the 3D electrokinetic technique and expand the application of the nanomagnetic materials for the purification of wastewater in the electrochemical process.

Supplementary material

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