Comparative assessment of compost and zeolite utilisation for the simultaneous removal of BTEX, Cd and Zn from the aqueous phase: Batch and continuous flow study

The present study focuses on the comparison of two materials, compost from municipal solid waste and natural zeolite for the simultaneous removal of petroleum hydrocarbons (benzene, toluene, ethylbenzene, xylenes - BTEX) and toxic metals from groundwater. First, batch experiments were conducted to identify the optimal removal conditions. All of the kinetic experiments were fitted to the pseudo-second-order kinetic model; equilibrium was reached within approximately 8 h for the zeolite and 12 h for the compost. An increase in the adsorbent dose and the pH value as well as a decrease in the initial concentration enhanced the pollutants' removal. The removal selectivity of both materials with slight differences follows the order Cd > Zn & toluene > ethylbenzene > m- & p-xylene > o-xylene > benzene. According, to the results derived from the continuous flow experiments the maximum adsorption capacity of the compost (90%) referred to Cd (0.88 mmol/g) whereas the minimum refers to benzene (65%) with a capacity up to 0.065 mmol/g. Zeolite had lower efficiencies for the studied pollutants with a higher performance corresponding to Cd (0.26 mmol/g), whereas the minimum zeolite capacity (63%) corresponds to toluene (0.045 mmol/g). Thus, this paper provides evidence that compost, a low cost material produced from waste, is capable for the simultaneous removal of both organic and inorganic pollutants from wastewater, and its performance is superior to zeolite.