Removal of Hg2+ From Desulfurization Wastewater By Tannin-Immobilized Graphene Oxide

A novel adsorbent by immobilizing tannic acid (TA) on graphene oxide (GO) was proposed and used to remove Hg 2+ from desulfurization wastewater. The morphology and physic-chemical property of tannin-immobilized graphene oxide (TAIGO) was characterized by Scanning electron microscopy (SEM), Atomic Force Microscope (AFM), and Fourier transform infrared spectroscopy (FTIR). The characterization results showed that the TA was immobilized on the GO successfully, and new functional groups were introduced on TAIGO. The effect of contact time, adsorbent dose, pH, and ion components on removal efficiency were evaluated. It was found that the adsorption process would complete within 15 min, and a higher removal efficiency could be obtained on the increased adsorbent dosage. The pH value would affect the protonation process of TAIGO and the form of Hg 2+ in the wastewater. The high-concertation Cl - and SO 3 2- would hinder the absorption performance, while SO 4 2- and cations had a negligible impact. Besides, an excellent economic benefit of TAIGO was achieved in the regeneration performance evaluation experiment, and removal efficiency of was 88% remained after three recycles. Most importantly, the TAIGO exhibited a better adsorption performance and economic benefit than GO and TA. The adsorption process was fitted with the pseudo-second-order kinetic model(R=0.9995), and the adsorption of TAIGO for Hg 2+ was mainly relies on the functional groups on GO and the chelation reaction between TA and Hg 2+ . These facts indicated that the TAIGO was a low-cost and high removal of Hg 2+ efficiency adsorbent, which could be further used in the practical desulfurization wastewater.