Synthesis of high-porosity hybrid geopolymer/alginate adsorbent for effective removal of methylene blue and optimization of parameters using RSM

Abstract

In this work, high-porosity geopolymer/sodium alginate (GSA) adsorbent was successfully prepared by entrapping fly ash-based geopolymer into sodium alginate (SA) using a simple method. The geopolymer slurry was firstly prepared which involved the utilization of sodium hydroxide (NaOH) as the alkaline activator followed by the addition of SA and albumen into the slurry. Natural albumen was used as the foaming agent. The effect of mass ratio of geopolymer to SA, albumen content (wt%), NaOH concentration and curing temperature (°C) on the removal of methylene blue (MB) was investigated using one factor at time (OFAT) method and optimized by response surface methodology (RSM), which achieved by 30 run of experiments using central composite design (CCD). A quadratic model was employed to correlate all the independent variables for maximizing the MB removal through the analysis of variances (ANOVA). The model suggested that the optimum condition for the preparation of GSA adsorbent for the efficient MB removal of 84.94% was achieved with mass ratio of geopolymer to SA was 1:0.13, albumen content of 25 wt%, NaOH concentration of 7 M and curing temperature of 60 °C. The albumen content was the most effective factor in the preparation of GSA adsorbent that increased the MB removal, followed by the curing temperature and mass ratio of geopolymer to SA.