ADSORPTIVE REMOVAL OF PARA-XYLENE BY RICE HUSK ASH

Abstract

The consequence of the rapid industrialization in developing countries since 20th century has emerged as a major threat to water pollution. Para-xylene is one of the most widely used chemical in chemical processes. It mainly used for preparation of tetrapthalic acid and diethyl tetrapthalate and as an antiknocking reagent in motor gasoline due to its high octane number (116.4). The huge demand of Para-xylene can be estimated from the fact that it is among the top 10 chemicals produced in U.S.A in terms of quantity according to the EPA source. Due to such increasing demand of production of Para-xylene, its adverse effect on environment is now a matter of great concern. Its emission into environment is contributed by various sources such as point sources like chemical and petrochemical manufacture, polyester manufacture, manufacture of paints and dyes and natural sources like petroleum, coal tar, plant emission etc. For the health point of consideration, the adverse effect of Para-xylene on human being is mostly chronical in nature. It has also high acute toxicity to aquatic life and is expected to moderately bioaccumulate in fish. From the various alternatives available for the removal of para-xylene from waste water, adsorption process is one, worth to be considered due to its probing track records for the removal of various hydrocarbons and aromatic compounds In the present study laboratory scale experiments have been carried out using the low cost rice husk ash as adsorbent for the removal of para-xylene. Batch experiments were carried out to determine the effect of various factors such as contact time, pH, adsorbent dose and temperature on adsorption process. Results obtained from these were interpreted in various ways like kinetic, isotherm and thermodynamic study to find out the economical and time appropriate feasibility of the process as well as various favorable conditions to carry out the process, then the feasibility of using RHA as an adsorbent has been determined. Equilibrium contact was found to be 100 min for Co < 150 mg/1 .Optimum removal of p-xylene onto RHA occurred at pH range 3.5±0.2. Optimum adsorbent dosage was found 9 g/1 RHA. The para-xylene adsorption follows pseudo-second-order kinetics. The adsorption isotherm of para-xylene onto RHA was represented by various isotherm models in which the Freundlich isotherm fitting the experimental data. The negative values of (AS°), (AH°); and (AG°) indicated feasible, exothermic, spontaneous nature of para-xylene adsorption on RHA.