The Studies of Adsorption Isotherms and Kinetics of Chromium Removal from Tannery Effluents using Cross-linked Chitosan obtained from Snail Shell
The Studies of Adsorption Isotherms and Kinetics of Chromium Removal from Tannery Effluents using Cross-linked Chitosan obtained from Snail Shell.
Chitosan is a natural polymer that has been employed in dye adsorption. In this work, adsorption and thermodynamic data for the interaction of Chromium in tannery effluent with chitosan in aqueous solutions were investigated. The equilibrium adsorption isotherms were determined, from 298 to 345 K. Adsorption data were adjusted to Langmuir, Freundlich, as well as Pseudo second order Kinetic model and van’t Hoff model of analysis of adsorption parameters.
The analysis showed that the Langmuir isotherm model was the most appropriate for fitting the experimental data, with a maximum monolayer adsorption of 33.3mg/kg at 298 K this value decreased with increase in temperature. The enthalpy of adsorption; ΔH, and the entropy; ΔS were – 13.54 kJ mol-1 and -0.1005kJ mol-1 K -1 respectively. The values demonstrated that the adsorption process was exothermic, favorable, and that randomness of the system decreased during the adsorption process.
The Freundlich adsorption model, gave favorable constants; Kf and n consistent with good adsorption process. The pseudo-second reaction model gave straight line plot with rate constant of 1.1673x 10-3 kg mg-1 min-1 and the qe was 29.85 mg/kg, this showed that the adsorption of Chromium ion by the chitosan followed the pseudo-second order kinetic model.
Many Industries such as textile, paper, plastics and dyestuffs, consume substantial volume of water and also use chemicals during manufacturing and dyeing to color their products. As a result, they generate considerable amount of polluted water depending on the type of process. Their toxic effluents are major source of aquatic pollution and cause considerable damage to the receiving water if discharged untreated.
During the past three decades, several waste water treatment methods have been reported and attempted for the removal of pollutants from tannery, textile, pulp and paper mill effluents. It is now recognized that adsorption using low-cost adsorbent is an economic method for water decontamination. A large variety of non-conventional adsorbent materials have been proposed and studied for their ability to remove toxic metals from waste water.
However, low-cost adsorbents with high adsorption capacity are still under development to reduce the adsorbent dose and minimize disposal problems. Much attention has recently been focused on various biosorbent materials such as fungal or bacterial biomass and biopolymers that can be obtained in large quantities and that are harmless to nature. Special attention is given to polysaccharides such as chitosan, a natural amino-polymer.
It is clear from the literature that biosorption of toxins using chitosan is one of the more frequently reported emerging methods for the removal of pollutants. In the past century, a rapid expansion in the chemical industries leads to increase in complexity of toxic effluents. Several industrial processes generate metal containing wastes. Heavy metal contamination has been a critical problem mainly because metals tend to persist and accumulate in the environment (Forstner, 1983).
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