Enhanced Selenate Removal in Aqueous Phase by Copper-Coated Activated Carbon.

Yonghong Wu,Qipeng Wang,Xinhai Zhao,Jianhong Zhang,Xuquan Huang,Cilai Tang,Aiqing Zhang

doi:10.3390/ma13020468

Abstract

In this study, we prepared a novel sorbent derived from precipitating copper ion onto the surfaces of activated carbon (Cu-AC). The sorbents were comprehensively characterized by Brunauer–Emmett–Teller (BET), zeta potential analysis, SEM, XRD, and FTIR. Batch experiments were conducted to evaluate selenate removal by Cu-AC under different conditions. The results showed that Cu was uniformly coated on the AC surface. Copper pretreatment markedly decreased the specific surface area and total pore volume of AC, and changed its surface zeta potential from highly negative to low negative and even positive. The Cu-AC substantially improved selenate adsorption capacity from the 1.36 mg Se/g AC of raw AC to 3.32, 3.56, 4.23, and 4.48 mg Se/g AC after loading of 0.1, 0.5, 1.0, and 5 mmol Cu/g AC, respectively. The results of toxicity leaching test showed AC coated with ≤1.0 mmol Cu/g was acceptable for potential application. Selenate adsorption was significantly inhibited by high ionic strength (>50 mM NaCl) and pH (>10). The electrostatic attraction between positive surface charge of Cu-AC and selenate ions and hydrogen bonding between CuO and HSeO4− might contribute to selenate sorption. Evidence showed that the selenate adsorption might involve outer-sphere surface complexation. The adsorption data appeared to be better described by Langmuir than Freundlich isotherm. The spent adsorbent could be effectively regenerated by hydroxide for reuse. Only a little decrease of removal efficiency was observed in the second and third run. This study implies that Cu-coated AC is a potential adsorbent for sustainable removal selenate from relative low salinity water/wastewater.

Highlights

Selenium (Se) is an essential micronutrient for many living organisms but it can be a potential toxicant to humans, livestock, and plants depending on its chemical species and dose [1,2,3]
After Cu coating at a dosage of 0.1 mmol Cu per gram activated carbon (AC) (Figure 1b), the AC surface was sporadically and uniformly deposited with small white particulate matters that were identified as a copper-bearing substance by energy dispersion spectrometer (EDS) analysis
Copper-coated AC adsorbents were prepared by simple precipitation process

Summary

Introduction

Selenium (Se) is an essential micronutrient for many living organisms but it can be a potential toxicant to humans, livestock, and plants depending on its chemical species and dose [1,2,3]. The increasing concerns over Se contamination from the wastewater of wet flue-gas-desulfurization (FGD) systems of coal-fired power plants have attracted more attention of the government and public [5]. Among many forms of Se, selenate (SeO4 2− ) is one of the most concerning forms because of its high chemical stability, mobility and bioavailability, and weak adsorption affinity to particles surface in the environment [6]. Several anaerobic biological treatment processes have been developed as a solution to treat selenate contaminated mining drainage and FGD wastewater [8]. Complexity, and other problems associated with the biological technologies are the major concerns and obstacles. The production of more bioavailable organic Se after biological treatment is a potential harm to the environment [9]. Finding a reliable and cost-effective Se solution is still a major challenge to water industry

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