Cr total removal in aqueous solution by PHENOTAN AP based tannin gel (TFC)

TFC was used for chromium ions (III and VI) adsorption from aqueous solution. The total chromium removal was strongly affected by pH changes and reached a maximum value at pH 1. The adsorption process was well described by the Langmuir model. The thermodynamic parameters exhibited the feasibility and the spontaneous nature of the adsorption. The optimum adsorbent dose obtained for chromium adsorption onto TFC was 0.1 g. The optimum contact time for chromium removal and treatment efficiency was 10 and 14 h, respectively. The kinetic studies showed that the adsorption process could fit into a pseudo-second-order model and the particle diffusion process was the rate-limiting step of the adsorption process. The desorbing agents studied did not show any promising result for the TFC regeneration process. The FT-IR results showed that the Cr(VI) removal onto TFC occurs through an indirect reduction mechanism. According to XPS spectrum, the majority of the adsorbed Cr is Cr(III), only a small quantity of Cr(VI) remains loaded on the TFC surface. (C) 2015 Elsevier Ltd. All rights reserved.