Removal of phenol from water environment by surfactant-modified alumina through adsolubilization

Abstract

Alumina was found to be a very efficient adsorbent for the removal of anionic surfactant (AS) from its highly concentrated wastewater. After removal of AS in several cycles, the exhausted surfactant-coated alumina becomes useless. This exhausted alumina, however, posses the ability to remove organic solutes from aquatic environment through the process called adsolubilization. In the present study, the exhausted alumina, hereafter designated as surfactant-modified alumina (SMA), was used for the removal of phenol from water environment. In the present study, the SMA was prepared by shaking alumina with sodium dodecyl sulfate (SDS; a representative member of AS) solution in batch study under optimized condition. The kinetic studies showed that 1.5 h shaking time was sufficient to achieve the equilibrium for phenol removal. The removal of phenol followed the second order kinetics. Studies were conducted to see the effects of SMA dose on the removal of phenol. The pH was maintained at 6.7 ± 0.1. SMA was found to be very efficient and ∼90% efficiency could be achieved under optimized conditions for the removal of phenol from phenol-spiked distilled water. This process is useful even when phenol is present at a very high concentration (5.32 × 10 −4 mol/L). The effects of various other parameters such as SDS coverage on alumina, pH, temperature, agitation speed, the presence of different ions (Cl −, NO 3 −, SO 4 2−, HPO 4 2−, Fe 3+ and Mg 2+) and humic acid on the phenol removal were studied. The pH < 7 favors the removal. It was observed that the removal efficiency was increased due to the presence of anions and was decreased a little due to the presence of cations. Temperature and humic acid had no effect on the removal of phenol. To test whether the removal of phenol was possible from wastewater using SMA, the adsorption study was conducted using synthetically prepared wastewater. The removal of phenol from distilled water and wastewater was comparable. Desorption of both SDS and phenol from the SMA surface was possible using 0.25 M sodium hydroxide solutions. Desorption of only phenol is possible by acetone or rectified spirit.