Adsorption of hexavalent chromium onto kaolin clay based adsorbent

• Published in: Journal of Central South University Vol. 21; no. 10; pp. 3918 - 3926
• Main Authors: Deng, Lin, Shi, Zhou, Luo, Lu, Chen, Shi-yang, Yang, Ling-fang, Yang, Xiu-zhen, Liu, Li-shan
• Format: Journal Article
• Language: English
• Published: Heidelberg Central South University 01-10-2014
• Subjects: Engineering; Metallic Materials; adsorption; isotherm; kaolin clay; Cr(VI); thermodynamics; kinetics; desorption
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-014-2379-4

A low-cost adsorbent modified kaolin clay (MKC) was synthesized and utilized for Cr(VI) removal from aqueous solution. Adsorption experiments were carried out as a function of adsorbent dosage, solution pH, Cr(VI) mass concentration, contact time, electrolyte, and temperature. It is found that the adsorption efficiency is high within a wide pH range of 2.5–11.5, and equilibrium is achieved within 180 min. Increases in temperature and electrolyte concentration decrease the adsorption. The adsorption follows the pseudo-second-order kinetic model. The Langmuir isotherm shows better fit than Freundlich isotherm. The maximum uptake capacities calculated from the Langmuir model are 15.82, 15.55 and 15.22 mg/g at 298, 308 and 318 K, respectively. Thermodynamic parameters reveals the spontaneous and exothermic nature of the adsorption. The FTIR study indicates that hydroxyl groups, NH
4
+
ions and NO
3
−
ions on MKC surface play a key role in Cr(VI) adsorption. The Cr(VI) desorbability of 86.53% is achieved at a Na
2
CO
3
solution. The results show that MKC is suitable as a low-cost adsorbent for Cr(VI) removal which has higher adsorption capacity and faster adsorption rate at pH close to that where pollutants are usually found in the environment.