Comparative Study for Adsorption of Acidic and Basic Dyes on Activated Carbon Prepared From Date Stone by Different Activation Agent

Abstract

This research includes a lab scale work to investigate the feasibility of treating waste water which is polluted with dyes exhausted from textile factory by using the adsorption process. Three types of activated carbon were prepared using locally available waste material (date stone). Chemical activation method with (zinc chloride, potassium hydroxide, or phosphoric acid) is used to prepare carbon. Firstly, the materials were carbonized at 275o C for 90 min, and then the carbonized materials were treated with (4 molar) solution of acid, base, or salt for 24 hours. Finally, these materials were activated at 600o C for two hours in the presence of nitrogen gas flow. The resulted activated carbons were checked by its (BET) surface area analysis and surface morphology by SEM. The surface area values were (815, 950,600) m2/g for carbon produced from the activation of date stone by phosphoric acid, potassium hydroxide, or zinc chloride respectively. SEM characterizations show that activated carbons that prepared from potassium hydroxide have higher surface area and good adsorption characteristics than that prepared from activation with phosphoric acid or zinc chloride. The adsorption process was carried out using two types of dyes. The first one is acidic (methyl orange) and the other is basic (bismark brown). The adsorption isotherms and kinetics were investigated for both dyes at temperatures (30, 40, 50, 60) o C for concentration range equal to (6-16) mg/l. The adsorption data of equilibrium were presented by using two common adsorption isotherm equations. The data was fitted fairly well with Langmuir isotherm for both dyes on all types of prepared activated carbons. The kinetics of adsorption was studied by using two kinetic equations, pseudo first order and pseudo second order. The results showed a rapid increase in the rate of adsorption at the initial until equilibrium achieved. The pseudo second order model represented the data very well with confidence level 0.99.