Investigation of Zinc removal capacities of different sorbent materials to be used in constructed wetlands

Abstract

It has been found over the past couple of years that health hazards associated with heavy metals havebeen on the rise, particularly the chronic diseases. Lack of tertiary treatment of wastewater may havecontributed to this emergent problem, mainly due to the high costs involved in the removal of heavymetals. Constructed wetlands have therefore received great attention as a tertiary treatment method ora polishing technique of wastewater due to its low construction and operation costs. However, findinga low-cost sorbent material to be used as the wetland filter material, which can be used as analternative to activated carbon, has been a problem for decades. Therefore, the present study focuseson applicability of low-cost sorbent materials: viz., clay tile, brick, saw dust and rice husks, as filtermediums. Laboratory-scale experiments were performed with a synthetic Zinc solution. Resultsrevealed that clay tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency,(98%), while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%)have relatively low adsorption capacities and removal efficiencies, respectively. The separation factorof equilibrium (RL) indicates favourable isotherms (0< RL<1) for all tested sorbent materials. Amongthe studied materials clay tile, brick and rice husks are good adsorbents for Zinc (n>2) while sawdustis a moderately difficult material for adsorption of Zinc (n <2).Keywords: adsorption isotherms, constructed wetlands, sorbent material, Zinc