Adsorption of Indole and Ortho-phenylenediamine on Activated Carbon

Abstract

Indole is a nitrogenous hetrocyclic compound has the bicyclic structure consisting of 6-member benzene ring fused with the 5- member nitrogen containing pyrrole ring has the formula C8H7N. It occurs naturally in human feces and has an intense fecal odor. Indole also get released from the meat industry during the fermentation of tryptophan. It is commonly used in industries such as agrochemicals, pesticides, cosmetics. Ortho-phenylenediamine (OPD) is an endocrine disrupting chemicals, and are widely distributed in environment. OPD is an aromatic amine, used as a component of polymers, pesticides, drugs, and dyeing intermediate compounds. In the present study adsorptive removal of Indole & OPD on activated carbon from aqueous solution have been investigated. For this, dosage study was carried out by varying the adsorbent dosages in the range of 0.5-5 g/100 ml at natural pH = 5.5 at 303 K. The adsorption of Indole & OPD was studied over a initial pH range of 2-9 at 303 K with optimum adsorbent dosage of 3 g/100 ml. Optimum conditions for the adsorptive treatment of Indole and OPD by activated carbon were found to be pHi-opt = 5.5, adsorbent dose of mad-opt=30 g/l and contact time = 4 hour, and at this optimum condition Indole and OPD removal were found up to 92.35% and 89.4%, respectively. To explore the effect of time on the adsorption process, kinetic study were performed at various Co values (25-50 mg/l) at optimum dosage of adsorbent m_(ad-opt )=30 g/l and optimum pH 〖(pH〗_(i-opt )=5.5), and experimental data were tested for their validation with pseudo-first-order and pseudo-second-order model with non-linear regression. Isothermal experiments were performed at 303 K, 313 K and 323 K with Co values of 10-100 ppm both for Indole and OPD with 〖pH〗_(i-opt ) and m_(ad-opt) of ACC. Various isotherms such as Freundlich, Langmuir and Redlich-Peterson (R-P) and Temkin were used to represent the adsorption equilibrium data.