Coagulation and flocculation process using cassava peel starch modified with lemongrass extract for pollutants removal in raw water

Sustainable and greener solution for water treatment problems is the persistent need in the current days. The present research synthesized a novel dual function coagulant using cassava peel starch with incorporation of lemongrass extract and evaluated the synergistic effect between alum and modified cassava peel starch (MCPS) or native cassava peel starch (CPS) as dual coagulants in removing turbidity, total suspended solids (TSS), chemical oxygen demand (COD) and Escherichia coli (E. coli) in raw water. The effects of pH, coagulant dosage and settling time on coagulation and flocculation performance of the coagulants were also determined. The coagulation and flocculation mechanisms were examined through floc characterization and electrokinetic analyses. Characterization study of coagulants confirmed the efficacy of modification technique as described by significant changes in pores formation, texture roughness and appearance of new element including Cl and Ca on the surface of the modified starch. The presence of citral, an important active group in lemongrass extract which responsible for antimicrobial property was also found in the modified starch. Coagulation and flocculation study indicated alum – MCPS and alum – CPS presented distinctive performance compared to alum, CPS and MCPS as sole coagulants of in terms of both coagulation and antibacterial functionality. Substantial removals of turbidity (93.15%), TSS (92.00%) and E. coli (100.00%) were achieved with treatment alum – MCPS within 10 minutes of settling time at effective alum – MCPS dosage of 4.50 – 70.00 mg/L and pH 7. Alum individually prevails over other coagulants in reducing COD (34.06%). Mechanism study indicated that charge neutralization is the main mechanism driving the coagulation process associated with alum. While bridging, ion exchange and complexation mechanism dominated the coagulation process associated with the starches. The favorable dual functionality of the coagulants provides a greener alternative in the effort to reduce the dosage of chemical coagulants and disinfectants, which in turn gives an impact on significant attenuation in the secondary pollution risk of chemical coagulants and disinfectant by-products.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

Universiti Tun Hussein Onn Malaysia

Year dc:date.issued

2020

Author dc:creator

• Mohd Asharuddin, Syazwani

• QD Chemistry

Language dc:language

en