TREATMENT OF BENZOIC ACID BEARING WASTEWATER

Abstract

Benzoic acid, the derivative of phenol, is considered to be versatile raw materials in chemical industry. Benzoic acid have high toxicity and solubility and they widely exist in the effluents of industries such as phthalic anhydride manufacturing plant, plastics and synthetics, pharmaceuticals, iron and steel manufacturing, petrochemical, petroleum refinery, purified terephthalic acid, etc. Wastewater containing benzoic acid has high oxygen demand and low biodegradability. The present study deals with the treatment of benzoic acid bearing wastewater by biological method and physico-chemical. Sequencing batch reactor (SBR) is a promising alternative for the biological treatment among the various biological processes. It is a time-based treatment process technology as compare to the conventional area-based activated sludge processes. Among physico-chemical methods, adsorption on to granular activated carbon (GAC) is considered to be one of the best methods. This study was done with the aim to study the removal of benzoic acid by biological treatment in SBR and by adsorption onto activated carbon. Laboratory scale SBR was used to optimize the operating conditions for the biodegradation of benzoic acid in SBR. The effect of operating parameters, namely mixed liquor suspended solids concentration (MLSS), initial organic loading rate, temperature, and aeration during fill phase have been studied. The results revealed that the highest benzoic acid removal efficiency of 92% for initial concentration 200mg/l was obtained at optimum conditions of MLSS=5000mg/l, temperature=30°C. In the adsorption study, the influence of various experimental parameters such as initial pH (pH° ), adsorbent dose, contact time, initial concentration and temperature where studied for the adsorptive removal of benzoic acid from aqueous solution by GAC. Optimum conditions for benzoic acid removal were found to be pH° 3.0, adsorbent dose 8 g/l of solution and equilibrium time = 8.0 h. The adsorption of benzoic acid onto GAC followed pseudo-second-order kinetics. Benzoic acid adsorption onto GAC was found to best represented by the Langmuir isotherm. The positive values of the change in entropy (AS°) and negative values of heat of adsorption (Al-I°); and negative value of change in Gibbs free energy (AG°) indicated feasible, exothermic nature of benzoic acid adsorption onto GAC.