Abstract

This paper presents experimental data on single and competitive adsorption isotherms for 1,2-dihydroxybenzene and maleic acid on activated carbon. Filtrasorb 400 activated carbon was used to adsorb 1,2-dihydroxybenzene and maleic acid, at temperature and pH in the range 15-35 °C and 2-8, respectively. Equilibrium data was determined after 30 h contact in stirred batch reactors, containing 0.5-5% w/w of activated carbon in water solutions of up to 50 mM organic compounds, both as single solutes or mixed. 1,2-dihydroxybenzene was chosen as a model because of its high toxicity and is a common constituent of industrial waste water. Results show that adsorption capacity for maleic acid and 1,2-dihydroxybenzene was around 4.5-5.3 (mmole/g), and 2.85-2.93 (mmole/g), respectively. In both cases, adsorption was not significantly affected by temperature within the range of conditions used here. Maleic acid adsorption seems more sensitive to pH. The maximum adsorption capacity for each model compound was found to decrease when the other solute was present in the solution, showing a significant competition for active sites on the carbon surface. Moreover, maleic acid was significantly outcompeted by 1,2-dihydroxybenzene. A Languir-type model for multicomponent systems was used here. This three parameters model yielded a good agreement between predicted and experimental data.