The potential of agricultural waste materials for the removal of synthetic dye, Phenol Red (PR) and Remazol Brilliant Blue R (RBBR) from aqueous solution was investigated. One of the major pollutants of water pollution, dyes, which not only result in enormous damage to the water body but also impact the organism's health, as it is highly toxic and carcinogenic by nature. Agricultural wastes are sustainable adsorbents since they are availability and low cost, which can also replace the traditional activated carbon. Therefore, this study investigated the removal of PR and RBBR from dye solution by adsorption onto the treated adsorbent. Two best out of ten adsorbents were chosen through a screening process using RBBR as a tested dye. Coconut shells (Cocos nucifera) and ambarella peels (Spondias dulcis) were selected as the main adsorbent of this study since they achieved the highest removal rate compared to others. With the selected adsorbent, the experiment was continued to study the effect of different initial dye concentration, adsorbent dosage, contact time, pH, and particle size on dye adsorption. Results show that different parameters can affect the removal rate and adsorption capacity of adsorbent in a different way. The adsorption of dye from aqueous solution onto adsorbent was evaluated using Fourier transform infrared spectroscopy (FTIR) to investigate the functional groups of adsorbent before and after the adsorption process, and it found that the functional group would affect the effectiveness or removal rate and adsorption capacity of adsorbents. The present study indicates that 99.82% of PR with an adsorption capacity of 1.05 mg/g can be removed by 5-gram ambarella peels. While coconut shells had removed 75.78% of RBBR with an adsorption capacity of 7.96 mg/g for 21 hours. The results proved that these agricultural waste were promising materials as an alternative adsorbent for the removal of dye from aqueous solution.
