Effectiveness of Sequential Pre-treatment and Application of High-porosity Hybrid Fly Ash Geopolymer/alginate Adsorbent for the Treatment of Batik Wastewater

In this work, hybrid fly ash geopolymer / alginate spheres (GSA) were produced and used as an effective and economical adsorbent in a treatment of batik wastewater. A preparation of GSA adsorbent involved a facile method where the fly ash (FA) based geopolymer was entrapped into sodium alginate (SA) followed by cross-linking of Ca^2+ and SA. In additional to that, natural egg white was utilized as a foaming agent. Characterization of the GSA adsorbent strongly confirmed the formation of hybrid spheres that composed of geopolymer and alginate with extremely porous microstructure with porosity of 87.64%. Surface area, average pore diameter and pore volume was 12.874 m^2 g^-1, 3.3110 nm and 0.1684 cm^3 g^-1, respectively. Prior to the adsorption process, the batik wastewater was pre-treated using high concentration acid hydrofluoric (HF) and magnesium oxide (MgO). The optimum acidification pre-treatment at pH=3 removed ~ 93% of chemical oxygen demand (COD). In the subsequent stage, the highest percentage of COD removal was ~27% by utilizing 1500 mg L^-1 of MgO powder. In the final stage, different dosages of GSA adsorbent was used in order to treat the remaining COD and resulted in as maximum as ~67% of the COD removal. According to the finding, the sequential pre-treatment and application of high-porosity hybrid GSA adsorbent offered a great potential to be implemented as an economical and effective batik wastewater treatment.