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Crab shell waste can cause pollution to the surrounding environment, but has the potential to be used as a biosorbent in the absorption of heavy metals, especially Pb because crab shells contain CaCO3 and chitin. Methods: Several variables that play a role in the biosorption process, among others: initial metal concentration, biosorbent mass, and contact time. Pb metal was determined by the Atomic Absorption Spectroscopy (AAS) method. Results: The results showed that the crab shell biosorbent contained Pb 0.019 mg/g. The concentration of Pb in the shell was used as a correction factor. Optimal result for parameter of initial concentration of Pb is 100 mg/L with efficiency percentage (99.11 ± 0.02)% and adsorption capacity (620.15 ± 0.3) ug/g. The optimal result of contact time is 120 minutes with efficiency percentage (91.22 ± 0.13)%. The optimal yield of biosorbent mass based on the percentage efficiency (98.01 ± 0.2)% is 2 grams. Conclusion: This study can show that crab shell waste can be used as an effective biosorbent for Pb metal adsorption. The results of the optimization of the best factors to be used in the biosorption process of Pb metal were the initial concentration of 100 mg/L, the mass of the biosorbent was 3 grams and the contact time was 110 minutes. The optimum conditions for Pb adsorption were successfully applied to seawater from the former bauxite mine.

The processing of bauxite ore into aluminium produces a large amount of waste materials. Red mud as waste from the alumina industry is a problem that damages the hydrological function of the soil. Red mud can still be utilised according to its composition and characteristics. In this study, red mud originating from Tanjungpinang is characterised using several techniques (Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), X-ray Diffraction (XRD), and Adsorption desorption nitrogen. XRD characterisation results for all samples tested, namely bmd1, bsg1, bsg2, and bsg3, have relatively uniform phases: boehmite, Gibbsite, Nepheline, Calcite, Hematite, and Quartz. The SEM-EDX test obtained data on the composition of the highest Al content found in bsg3 with a weight of 7.2%. Adsorption desorption nitrogen test results obtained bsg3 has the highest surface area with 62,423 m2/g. With the characteristics of red mud from bauxite washing, this waste material can be utilised in various fields.