Siti Mazatul Azwa Saiyed Mohd Nurddin, Suriati Sufian and Nurul Ekmi Rabat
Keywords: high-porosity, hybrid, geopolymer, alginate, batik wastewater
Abstract: In this work, high-porosity hybrid fly ash (FA) geopolymer/alginate (GSA) adsorbent was produced and used as an effective and economical adsorbent in the treatment of batik wastewater. The GSA adsorbent preparation involved a simple method where the FA based geopolymer entrapped into sodium alginate followed by cross-linking of Ca2+ ion and sodium alginate (SA). Additional to that, natural egg white was utilized as the foaming agent. The geopolymer slurry was firstly prepared by using sodium hydroxide (NaOH) as the alkaline activator with mass ratio of FA to NaOH was 3:1. Then, SA solution (2.0 wt%) was mixed with the geopolymer slurry prior to the addition of egg white. Finally, the slurry was added dropwise in calcium chloride (CaCl2) solution (2.0 wt%) and the formed beads were kept in the solution for 24 h at room temperature. The GSA beads with the diameter 2-4 mm were drained, washed and cured at 60°C for 24 h. The detail characterization of GSA strongly confirmed that the developed material was hybrid geopolymer/alginate bead with extremely porous microstructure which porosity was 87.64%, and surface area, average pore diameter and pore volume was 80.60 m2/g, 3.3110 nm and 0.0466 cm3/g, respectively. In the adsorption process, batik wastewater from a batik factory in Terengganu was sequentially pre-treated prior to treatment by the GSA adsorbent. The adsorption indicated that the GSA adsorbent possessed an excellent chemical oxygen demand (COD) and American Dye Manufacturers Institute (ADMI) colour degree removal efficiency which fulfilled the Seventh Schedule (Regulation 12) of Environmental Quality (Industrial Effluents) Regulation 2009. Furthermore, the removal of the heavy metals in the batik wastewater was also complied with the Standard A and Standard B of Fifth Schedule (Regulation 11) of Environmental Quality (Industrial Effluents) Regulation 2009. Hence, the high-porosity hybrid GSA adsorbent has a great potential to be implemented as an economical and effective batik wastewater treatment. Apart from having the advantage of being prepared from industrial by-product material, the GSA adsorbent was also found to be feasible for treating batik wastewater which can be directly used in packed beds.
