Removal of crystal violet dye from wastewater by surfactant-modified alumina

Abstract

Sodium dodecyl sulfate (SDS), an anionic surfactant (AS) was used for the surface modification of neutral alumina. Micelle-like structures are formed on the surface of alumina, which are capable of removing organic pollutants from water environment. The surfactant-modified alumina (SMA) was used for the removal of crystal violet (CV), a well-known cationic dye from aquatic environment. The kinetic studies showed that 1 h shaking time was sufficient to achieve the equilibrium. The removal of CV followed the second order kinetics. Studies were conducted to see the effects of adsorbent dose and initial CV concentration on the removal of CV using SMA. The pH was maintained at 6.7 ± 0.1. SMA was found to be very efficient adsorbent, and ∼99% efficiency could be achieved under optimised conditions for the removal of CV when present even at a high concentration (200 ppm). The effects of various other parameters such as pH, temperature, the presence of different ions (Cl −, NO 3 −, SO 4 −2, HPO 4 −2 and Fe 3+), and humic acid on the CV removal were also studied. The pH in the range of 7.0–8.5 favours the removal. It was observed that the removal efficiency was increased due to the presence of anions and humic acid and was decreased due to the presence of cations. Temperature had no effect in this process. To test whether the removal of CV was possible from real water using SMA, the adsorption study was conducted using CV spiked samples using distilled water, tap water and synthetically prepared wastewater. It was interesting to note that the removal efficiency was even better for tap water and much better for wastewater when compared to that using distilled water. Desorption of CV from the SMA surface was possible using 1 M sodium hydroxide solution, rectified spirit and acetone.