A combined adsorption and ozonation process for removal of lindane in aqueous medium

Abstract

Gamma-hexachlorocyclohexane or lindane (?-HCH) removal using a combination method of adsorption and ozonation was investigated. Lindane is one of the persistent organochlorine pollutants (POPs), used as a pesticide commonly in agricultural industry. The combination of both methods was studied based on adsorptive capability of banana fronds activated carbon which act as an adsorbent and powerful ozonation agent. The raw banana frond was impregnated with ZnCI2 prior to the process of carbon activation. Gas Chromatography-Flame Ionization Detector (GC-FID) equipment was used to analyze the concentration of lindane solution before and after treatment. The formation of ozone in aqueous solution was studied by using Ultraviolet-Visible Spectrophotometry (UV-Vis). The study showed that the highest removal of lindane was achieved at 91% by using the adsorption method, 92% by using ozonation method and 99% by using a combination of both methods. The equilibrium data of adsorption was analyzed using two isotherm models Langmuir and Freundlich, and Langmuir isotherm (R2 = 0.99) was found to fit the data better than Freundlich isotherm. The adsorption kinetics was studied, and the study indicated that the kinetic model followed pseudo-second-order (R2 = 0.99). The functional groups of adsorbents were investigated using Fourier Transform Infrared Spectroscopy (FTIR), and it was found that a large number of carbonyl groups that represent hydrogen bond and hydroxyl groups had influenced the capability of adsorption by the banana fronds activated carbon towards lindane. In addition, the surface morphology of adsorbent was investigated using Field Emission Scanning Electron Microscope (FESEM). The study showed an increment of available pore sites after carbon activation of raw banana fronds soaked with ZnCI2. Brunauer-Emmett-Teller (BET) supported by the FESEM results shows 4.86 m2/g and 4.77 m2/g of available pore sites for banana fronds activated carbon with and without impregnation of ZnCI2 activated carbon, respectively. The results proved that the combination method of adsorption and ozonation is a highly potential method for the removal of lindane in aqueous solution.