Effectiveness of Natural Coagulants in Purification of Industrial Wastewater: A case of Cactus Pads and Watermelon Seeds

Abstract

This study assessed the potential of cactus pads and watermelon seeds as natural coagulants in industrial wastewater treatment. The global characterization of the two coagulants was done by using the Fourier Transform Infrared (FTIR) to determine the specific functional groups and by zeta potential measurements. A full factorial design was used to design the experiment and analyze the effect of three factors: coagulant dosage, settling time and particle size with three levels each and one replicate on the turbidity removal. ANOVA analyses were used to determine the significance of the factors. Results show that the amino and hydroxyl groups in cactus pads and watermelon seeds generate surface charges that enable interaction with charged particles and facilitate their destabilization, promoting coagulation. Negative zeta potential due to the ionization of the functional groups signified the potential of the cactus pads and watermelon seeds as natural coagulants. The highest removal efficiency achieved was 92% for both watermelon seeds and cactus pads, using a dose of 200 mg/L and 140 mg/L, respectively. The main effect and interaction plots for both coagulants reveal that an increase in both factors significantly impacted the removal efficiency. Results on particle size effects imply that larger particles have a greater tendency to settle and can be easily removed, resulting in the highest removal effectiveness. The combination of cactus pads and watermelon seeds was found to be significantly more effective in reducing turbidity in wastewater from industries, with a clearance rate of approximately 94%. More studies on the synergistic effect of combining the two coagulants are necessary. Utilizing cactus pads and watermelon seeds, for treating industrial wastewater can decrease reliance on and minimize the need for importing synthetic coagulants, which have negative environmental effects and pose significant health risks.