Reduction of Phosphate from Surface Water Using Natural Adsorbents

摘要

The increased content of phosphorus in a water ecosystem leads to extensive algae growth or eutrophication. So removal of phosphate from surface water is crucial. We have conducted a column study using two different adsorbents: Crab Shell-Sand and Vermiculite. Experiments were done with the phosphate stock solution prepared from potassium di hydrogen phosphate. Crab Shell (0.5 mm)-Sand (1:1) and Vermiculite (0.5 mm) with flow rates 2 mL/min showed maximum removal efficiency of 93.1％ and 95.7％ respectively. Exhaustion time for Crab Shell-Sand was 32 h and Vermiculite was 20 h. Thomas model was used as an isotherm, maximum adsorption capacity of Crab Shell-Sand and Vermiculite were 24.53 mg/g and 16.29 mg/g. After 8 days it is found that the Crab Shell column gets clogged due to bio fouling which reduces the flow rate and cause bad odor. Hence, Vermiculite was considered as a better optimal adsorption material. Regeneration of Crab Shell-Sand can withstand only up to 3 cycles but Vermiculite can withstand up to four cycles. Finally, pond water was tested in both the column of Crab Shell-Sand (1:1) and Vermiculite which shows same results as that of using phosphate stock solution in the column. SEM analysis was also proved the adsorption-desorption of phosphate onto Crab Shell and Vermiculite.