REMOVAL OF 2-4 DICHLOROPHENOL USING VARIOUS ADSORBENTS

Abstract

2,4 dichlorophenol as one type of the most hazardous materials they are, mutagenic and resistant to biodegradation, and thus have to be decomposed before discharging into receiving waters, in order to avoid the biomagnified toxicity to aquatic flora and fauna through various food chains. Many efforts have been made for the physico-chemical and/or biological treatments of 2,4dichlorophenol rich waste waters Chlorophenols are organic chemicals formed from phenol by substitution in the phenol ring with one or more atoms of chlorine Among all the dichlorophenols C6H4C120 it is 2,4 dichlorophenol that is produced in greater quandity.2,4 dichlorophenols used in the manufacture of 2,4 dichlorophenoxy propionic acid (2,4DP), 2,4 dichlorophenoxy acetic acid (2,4D). Industrially 2,4dicholorophenol is obtained by chlorinating phenol, p-chlorophenol, o-chlorophenol or mixture of these compounds in cast iron reactors. The chlorinating agent may be chlorine or surfuryl chloride in combination with Lewis acid There are several methods for removing toxic 2,4dichlorophenols from aqueous solutions, such as adsorption, membrane filtration, solvent extraction, chemical oxidation , biological teratmnet.Removal of 2,4dichlorophenol from contaminated water bodies has been attempted by several researchers employing a wide variety of techniques. Majority of these are adsorption on various surfaces like activated carbon, peat, agricultural waste In the present study laboratory scale experiments have been carried out using the Coconut shell activated carbon (CSAC) and Commercial activated carbon (CAC), Bagasse fly ash (BFA), Rice husk ash (RHA) and mixed activated carbon (MAC) as adsorbents for the removal of 2,4dichlorophenol. The present study has been undertaken with the objective to investigate the suitability of BFA, RHA, CSAC and MAC as a low cost adsorbent for the removal of 2,4dichlorophenols as replacement of CAC. Batch experiments were carried out to determine the effect of various factors such as contact time, initial iii concentration, pH, adsorbent dose, adsorbent particle size and temperature on adsorption process. Kinetic study shows that adsorption of 2,4dichlorophenols on CSAC and CAC,BFA, RHA and MAC, follows the Pseudo- second order kinetics. Langmuir isotherm best-fitted the isotherm data for 2,4dichlorophenol adsorption on CSAC, CAC, MAC, RHA and BFA at almost all temperatures. However, the error analysis values and the non-linear correlation coefficients, R2, are comparable for Langmuir, Temkin and Freundlich isotherm. Adsorption increases with increase in temperature for all the adsorbents, showing the endothermic nature of adsorption. From thermodynamic study AG° , AI-1° and AS° values are also calculated for CSAC,CAC, MAC, RHA and BFA adsorbents The order of removal of 2,4dichlorophenol CAC>BFA.>RHA>MAC>CSAC. Due to less surface area and the least number pores of coconut shell activated carbon (CSAC) the amount of removal is low among all the adsorbent s apart from that all the adsorbent s proved to be effective CAC was adjudged to be the best adsorbent with 93% removal of 2,4 dep at pH 4 and 30°C temperature and S g/1 adsorbent dose. This was followed by BFA(86%) MAC(83.4%) and RHA (83%) at nearly similar conditions