Manaskorn Rachakornkij, Sirawan Ruangchuay, and Sumate Teachakulwiro

pp. 13 - 24

Abstract

Bagasse fly ash, a waste from the sugar industry, was investigated as a replacement for the current
expensive methods of removing reactive dyes (Remazol Black B; RBB, Remazol Brilliant Blue R; RBBR, and
Remazol Brilliant Red F3B; RBRF3B) from aqueous solutions. Bagasse fly ash was collected from a local
sugar factory in Saraburi province, Thailand. It was oven dried at 110ºC overnight and sieved to the desired
particle size of 150 µm or smaller. The 50 mL plastic conical tubes containing solution and bagasse fly ash
were shaken at room temperature (27±2ºC). The pH values of solutions were adjusted by addition of HNO3
and NaOH. The batch study indicated that initial pH of aqueous solutions did not affect dye removal. While
the removal efficiency decreased with increasing initial concentration, it increased with increasing adsorbent
concentration. The best adsorptions were obtained under condition of 50 mg/L concentration, original pH
solution of about 5, and 240, 300, and 240 minutes contact time for RBB, RBBR, and RBRF3B, respectively.
Most adsorption experiments showed in the range of about 50% to 98% removal; that is, the efficiencies of
RBB, RBBR, and RBRF3B adsorption were found to be between 58.48-98.03%, 46.15-93.47%, and 46.30-
94.60%, respectively. For the linear and nonlinear forms of the Langmuir and Freundlich models, the results
indicated that the Langmuir adsorption isotherm fitted the data better than the Freundlich adsorption isotherm. Adsorption of these dyes onto bagasse fly ash was favorable sorption. Therefore, bagasse fly ash, the
low-cost agricultural waste in Thailand, is suitable for use as adsorbent for RBB, RBBR, and RBRF3B under
this investigation.