Comparative Adsorption Study of Acid Violet 7 and Brilliant Green Dyes in Aqueous Media using Rice Husk Ash (RHA) and Coal Fly Ash (CFA) Mixture

One of the concerns in wastewater pollution is the presence of colored compounds, such as dyes. Acid violet 7 (AV7) and brilliant green (BG) are examples of synthetic dyes that have been used in various applications. In this work, a comparison of AV7 and BG dye adsorption was investigated using an adsorbent prepared from the mixture of rice husk ash (RHA) and coal fly ash (CFA). The attention was focused on the major batch adsorption parameters, which include adsorbent dosage, initial dye concentration, contact time, pH, shaking speed, and temperature. A lesser amount of RHA-CFA adsorbent was found to be used for adsorbing the same concentration of BG as compared to AV7. In contrast to AV7, the adsorption of BG rapidly attained equilibrium. The effective pH for BG removal is in the pH range of 6–8, while the highest AV7 removal was obtained at a low pH value. The adsorption removal for AV7 and BG increases with rising shaking speed and temperature. Scanning electron morphology (SEM) analysis showed the morphological porous structure on the RHA–CFA adsorbent surface. X-ray diffraction (XRD) analysis indicated the presence of complex compounds containing cristobalite, quartz, and mullite compounds in the RHA–CFA adsorbent. The study revealed that RHA–CFA adsorbents can remove AV7 and BG from an aqueous medium.