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In this study, spent tea leaves (STL) bio-char was investigated to adsorb malachite green dye in aqueous solution. The adsorption parameters were optimised by central composite design (CCD). Three independent process variables namely adsorbent dosage, initial dye concentration and contact time were selected as input parameters while the percentage of MG removal was considered as response. The most important effect on the bio-sorption performance was found to be the adsorbent dosage followed by the contact time. The optimum operating conditions for the removal of MG dye using STL bio-char were determined at 0.18 g adsorbent dosage, 46.92 mg/L of initial dye concentration and contact time of 56.16 minutes. At this optimum conditions, the percentage of MG removal up to 98.92% with desirability of 1.000. Thus, it can be concluded that STL bio-char can significantly be an alternative for the removal of MG dye from aqueous solution.

Conventional methods to remove heavy metals from polluted water are expensive and not environmentally friendly. Therefore, this study was carried out to investigate the potential of agricultural waste such as pineapple peel (Ananas Cosmos) as low-cost absorbent to remove heavy metals from synthetic polluted water. The results showed that Cd, Cr and Pb were effectively removed by the biosorbent at 12g of pineapple peels in 100 mL solution. The optimum contact time for maximum adsorption was found to be 90 minutes, while the optimum pH for the heavy metal’s adsorption was 9. It was demonstrated that with the increase of adsorbent dosage, the percent of heavy metals removal was also increased due to the increasing adsorption capacity of the adsorbent. In addition, Langmuir model show maximum adsorption capacity of Cd is 1.91 mg/g. As conclusions, our findings show that pineapple peel has potential to remove heavy metal from polluted water.