Bentonite-supported nanoscale zero-valent iron granulated electrodes for industrial wastewater remediation

Abstract

Bentonite-supported nanoscale zero-valent iron (B-nZVI) granulated electrodes were synthesized for remediation of pulp and paper wastewater as part of a three-dimensional (3D) electrode system. Results of scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) suggested that the layered structure of bentonite can reduce the aggregation of nZVI effectively. X-ray diffraction (XRD) results indicated that bentonite can effectively prevent the nZVI from being oxidized. The potential of zero charge (PZC) and cation exchange capacity (CEC) suggested that B-nZVI has good adsorption performance and reactivity to remediate the pollutants in pulp and paper wastewater. The 3D electrode system exhibited high efficiency in reducing COD and color to meet emission standards. The optimum conditions were as follows: current density = 40 mA cm⁻², electrolysis time = 50 min, distance of electrode plates = 4 cm, granulated electrode dosage = 2 g L⁻¹ and initial pH = 3.0. The maximum removal efficiencies of COD and color were 85.1% and 97.5%, respectively.