Utilization of bagasse and bagasse fly ash as adsorbents for removal of lead and chromium and subsequent utilization as construction materials

Abstract

Cogeneration of steam and electricity is a standard practice in the sugarcane industry worldwide. For Thailand, 22% of the small power producers (SPPs) use bagasse as a fuel, thus generating a large quantity of fly ash and residues. The purpose of this research is to convert bagasse (B) and bagasse fly ash (BFA) into inexpensive and effective removal materials for lead (Pb) and chromium (Cr) and to assess the efficiencies of cementitious solidification of spent materials for disposal in landfill and to develop construction materials namely; interlocking concrete paving blocks and hollow non-load- bearing concrete blocks. The batch study results indicated that removal efficiency of Pb, total Cr, and Cr (VI) increased with increasing contact time, and amount of material applied. The maximum removals of Pb and Cr were obtained at pH 6 and pH 1, respectively. BFA was a better adsorbent for Pb than B. The removal of Cr(VI) may involve two processes, namely, reduction of Cr(VI) to Cr(III) and adsorption of Cr(VI) and Cr(III). Reduction was likely the major Cr(VI) removal mechanism than adsorption in B while the reverse was true for BFA. The hydroxyl groups in cellulose structure of B were found to be the potential major reduction sites. Portland cement hydration was inhibited by the increase in the amounts of B and BFA, resulting in poor strength performance. The compressive strengths increased with curing time and a 3-day curing period was enough to meet the strength requirement of landfill standards (3.5 ksc) for 5 and 10% replacement with B and BFA respectively. Concentrations of lead and chromium in leachate form all solidified products were below the limits (5 mg/L) established by the Ministry of Industries No.6, B E. 2540 (1997). BFA has high efficiency for partial cement replacement up to 30% in interlocking paving concrete block and hollow non-load-bearing concrete block construction. This alternative treatment process may very well be the choice for Pb or Cr removal. It utilizes wastes from other factory to treat waste. This is an example of comprehensive waste management suitable for sustainable development.