Recovering heavy metals from electroplating wastewater and their conversion into Zn(2)Cr-layered double hydroxide (LDH) for pyrophosphate removal from industrial wastewater.

Affiliation

Fu D(1), Kurniawan TA(2), Avtar R(3), Xu P(4), Othman MHD(5).
Author information:
(1)Key Laboratory of Mine Water Resource Utilization of Anhui Higher Education Institute, School of Resources and Civil Engineering, Suzhou University, Suzhou, 234000, Anhui, PR China; College of the Environment and Ecology, Xiamen University, Xiamen, 361102, Fujian province, PR China.
(2)College of the Environment and Ecology, Xiamen University, Xiamen, 361102, Fujian province, PR China; China-ASEAN College of Marine Sciences, Xiamen University Malaysia, Selangor Darul Ehsan, 43900, Malaysia. Electronic address: [Email]
(3)Faculty of Environment Earth Sciences, Hokkaido University, Sapporo, 060-0810, Japan.
(4)Key Laboratory of Mine Water Resource Utilization of Anhui Higher Education Institute, School of Resources and Civil Engineering, Suzhou University, Suzhou, 234000, Anhui, PR China.
(5)Advanced Membrane Technology Research Centre
(AMTEC), School of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia.

Abstract

This work incorporated technological values into Zn2Cr-layered double hydroxide (LDH), synthesized from unused resources, for removal of pyrophosphate (PP) in electroplating wastewater. To adopt a resource recovery for the remediation of the aquatic environment, the Zn2Cr-LDH was fabricated by co-precipitation from concentrated metals of plating waste that remained as industrial by-products from metal finishing processes. To examine its applicability for water treatment, batch experiments were conducted at optimum M2+/M3+, pH, reaction time, and temperature. To understand the adsorption mechanisms of the PP by the adsorbent, the Zn2Cr-LDH was characterized using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses before and after adsorption treatment. An almost complete PP removal was attained by the Zn2Cr-LDH at optimized conditions: 50 mg/L of PP, 1 g/L of adsorbent, pH 6, and 6 h of reaction. Ion exchange controlled the PP removal by the adsorbent at acidic conditions. The PP removal well fitted a pseudo-second-order kinetics and/or the Langmuir isotherm model with 79 mg/g of PP adsorption capacity. The spent Zn2Cr-LDH was regenerated with NaOH with 86% of efficiency for the first cycle. The treated effluents could comply with the discharge limit of <1 mg/L. Overall, the use of the Zn2Cr-LDH as a low-cost adsorbent for wastewater treatment has contributed to national policy that promotes a zero-waste approach for a circular economy (CE) through a resource recovery paradigm.