Comparative study on synchronous adsorption of arsenate and fluoride in aqueous solution onto MgAlFe-LDHs with different intercalating anions

Lu Hongtao; Liu Shuxia; Zhang Hua; Qiu Yanling; Yin Daqiang; Zhao Jianfu; Zhu Zhiliang

doi:10.1039/c8ra05968c

Comparative study on synchronous adsorption of arsenate and fluoride in aqueous solution onto MgAlFe-LDHs with different intercalating anions

RSC Adv. 2018 Sep 27;8(58):33301-33313. doi: 10.1039/c8ra05968c. eCollection 2018 Sep 24.

Authors

Lu Hongtao^{1

2}, Liu Shuxia¹, Zhang Hua¹, Qiu Yanling³, Yin Daqiang³, Zhao Jianfu¹, Zhu Zhiliang^{1

3}

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, Tongji University Shanghai 200092 China.
² Postdoctoral Research Station, College of Civil Engineering, Tongji University Shanghai 200092 China.
³ Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University Shanghai 200092 China zzl@tongji.edu.cn +86-21-6598 4626 +86-21-6598 2426.

Abstract

In this study, a series of MgAlFe-LDHs (Cl^-, NO₃ ^-, intercalation, and calcined products of a CO₃ ^2- interlayer) was synthesized and used for adsorption of arsenate and fluoride in individual contaminants and coexisting pollutant systems. Effects of various factors such as initial pH of solution, dosage of materials, coexisting ions, contact time, and initial pollutant concentrations were evaluated. Experimental results showed that different intercalating anions had a significant effect on adsorption performance of arsenate and fluoride in water. The adsorption of arsenate and fluoride on MgAlFe-CLDH, MgAlFe-Cl-LDH or MgAlFe-NO₃-LDH can be described by different adsorption isotherm equations. During the simultaneous removal process, arsenate and fluoride competed for adsorption sites of the adsorbent materials, and the fluoride ions had advantages in the competitive adsorption on MgAlFe-Cl-LDH and MgAlFe-NO₃-LDH. MgAlFe-NO₃-LDH was used to adsorb arsenate and fluoride in coexisting pollution systems (the concentration of each pollutant was 2 mg L^-1, the adsorbent dosage was 1.5 g L^-1). The remaining arsenic concentration was reduced to less than 10 μg L^-1 and the remaining fluoride ion concentration to below 20 μg L^-1 which meets the World Health Organization's, EPA's and China's drinking water standards for arsenic and fluoride limits. A possible mechanism is discussed with support from further XRD, SEM, and XPS analysis of the materials after their adsorption.