Hybrid sorbent (LDHs–polymer composite) for the adsorption of chromate from aqueous solution

• Published in: Desalination and water treatment Vol. 57; no. 57; pp. 27741 - 27753
• Main Authors: Ha, Ho Nguyen Nhat, Phuong, Nguyen Thi Kim, Tho, Nguyen Thi Mai
• Format: Journal Article
• Language: English
• Published: Abingdon Elsevier Inc 01-12-2016; Elsevier Limited
• Subjects: Adsorbents; Adsorption; Adsorption isotherm; Adsorption kinetic; Anions; Aqueous solutions; Chromate removal; Chromates; Chromium; Composite materials; Fixed-bed column; Hydroxides; Isotherms; Layered double hydroxides–polymer composite; Mathematical models; Polymer matrix composites; Polymers; Water treatment; Layered double hydroxides–polymer composite; Fixed-bed column; Chromate removal; Adsorption kinetic; Adsorption isotherm
• ISSN: 1944-3986; 1944-3994; 1944-3986
• DOI: 10.1080/19443994.2016.1175970

In this study, the performance of layered double hydroxides–polymer (LDHs–polymer) composite as an adsorbent for the removal of hexavalent chromate ion from aqueous solution was investigated. The LDHs–polymer composite was prepared by immobilizing LDHs into spherical alginate/polyvinyl alcohol (PVA)–glutaraldehyde composite (spherical polymer composite). Approximately 90.0–92.5% of chromium was removed by LDHs–polymer composite from an aqueous solution containing 45 mg Cr/L. The adsorption data were well explained by the pseudo-second-order kinetics model and the Langmuir isotherm model. The adsorption capacities of these LDHs–polymer composite were from 1.358 to 1.471 mg Cr/g at pH 7, as calculated from the Langmuir adsorption isotherm. The adsorption ability of the LDHs–polymer composite decreased by approximately 5–6% after five adsorption–desorption cycles. Significant reduction of the chromate removal was observed in the presence of carbonate and phosphate ions. The effect of co-existing anions on the chromate adsorption capacity followed in the order: CO32-≈PO43->SO42-≈ Cl−. A fixed-bed column study was conducted with a real-life chromium-bearing plating wastewater sample. The breakthrough time was found to be from 5.5 to 7.5 h. Under optimized conditions, the LDHs–polymer composite removed more than 83–88% of total chromium in the solution. The results obtained in this study will be useful for further extending the adsorbents to the field scale or for designing pilot plants in future studies. From the viewpoint of environmental friendliness, the LDHs–polymer composite are a potential cost-effective adsorbent for chromate removal in water treatment.