Assessing the effectiveness of groundnut shell & water hyacinth bio-adsorbent in cadmium removal from steel rolling mills wastewater.

Abstract

In the current study, the capacity and efficacy of water hyacinth, ground nut shell and their blended composite to remove cadmium ions from steel rolling mills wastewater was investigated. Bio-adsorbent were burnt under extreme temperatures to formulate biochar materials by thermal decomposition. Material A, WHA was prepared by using water hyacinth ash, while for material B, GNS by using Ground nut shell ash, BMA a mixture of equal amounts of the two ashes of WHA & GNS were used. Batch experiments was carried out to determine the effect of initial PH, contact time (t) and adsorbent dose on percentage removal of Cd2+ by bio-adsorbent biochar. The optimum conditions were determined using Taguchi statistical approach. The maximum removal efficiency values (93.18% Cd2+) were obtained at pH 6.5 in 60 min with 2 g of GNS and initial metal concentration of 1.92 mg L–1 forCd2+. The most influential factor on bio sorption is adsorbent dose with a percentage contribution of 93.18%, 91.88% and 90.94% for GNS, WHA, BMA respectively. Amongst the low cost bio-sorbents, GNS presents the lowest cost per gram of heavy metal removed, 4.8 Ugx/g, while WHA is the second less expensive bio sorbent with a cost of 5.2 Ugx/g. BMA presents a slightly high cost (5.4Ugx) per gram of Cd (II) removed. Key Words: Water Hyacinth, Bio sorption, Ground Nut Shell, Taguchi method, Heavy Metal