Investigations on arsenic adsorption onto dolomitic sorbents

Arsenic is present in potable water in many areas in the world as a result of both natural impacts and anthropogenic discharge, with arsenic bearing waters requiring proper treatment before use. At present, there is a considerable interest in studying new sorbent materials for the removal of arsenic from aqueous solutions. This work discusses the feasibility of arsenic uptake onto raw dolomite which is considered to be a potential inexpensive adsorbent. Experimental investigations were undertaken in equilibrium isotherm and kinetic systems in order to evaluate the adsorption capacity by taking into consideration the experimental parameters such as: pH; initial solute concentration; massvolume ratio; particle size of adsorbent; contact time, the effect of various ions present and the effect of changing the temperature. The equilibrium time was determined to be 5 days for dolomite. Desorption studies were also undertaken. The data for the dolomite-As were compared with granular activated carbon in an identical set of experiments. The data were mathematically described using empirical equilibrium isotherm models, namely Langmuir and Freundlich models. The maximum arsenic removal with dolomite was found at pH 2 and was dependent on the dosage of dolomite, adsorbent particle size and the presence of various anions. For the kinetic Experiments the data were mathematically described using adsorption kinetic models, namely pseudo first-order and pseudo second-order models. Thermodynamic results indicate that the adsorption follows an exothermic chemisorption process. The experimental data indicate successful removal of As(V) ion from aqueous solution indicating that dolomite may be an alternative low cost adsorbent for As(V).