Synthesis and efficacy of cactus-banana peels composite as a natural coagulant for water treatment

Abstract

Aluminium and ferric salts continue to be used as coagulants in drinking water treatment. Natural coagulants can be used for the same purpose because they are cheaper, locally accessible and environmentally friendly. However, low production yields and high operation costs affect commercial adoption of natural coagulants from individual plants, hence the exploration of performance of their composites. This study evaluated the performance of cactus-banana peels composite as natural coagulant for water treatment because of the low cost nature of the two plants. Design Expert Software was used to design jar test experiments for attainment of optimum mixing ratio of the composite for determining optimum dosage, pH and extraction time for development of performance models. Performance of the coagulant was evaluated based on removal efficiencies of turbidity, total suspended solids (TSS) and Escherichia coli (E.coli). The goodness of fit for developed models was evaluated using R2 values and adequate precision. The optimal composition of the composite was cactus to banana peels ratio 0.62:0.38. The optimally mixed powder had a bulk density of 590 kg/m3 while the extracted liquid coagulant had pH and electrical conductivity of 7.05 and 1123 μs/cm, respectively. The optimum dosage, pH and extraction time were 12.25 ml/l, 7.31 and 26.53 min, respectively. Turbidity, TSS and E. coli removal efficiencies were 87.13, 82.15 and 84.02%, respectively. These results indicated good performance of the composite coagulant in water treatment compared to 82–99% for alum, the most commonly used commercial coagulant.