Potential of Luffa cylindrica seed as coagulation-flocculation (CF) agent for the treatment of dye wastewater: Kinetic, mass transfer, optimization and CF adsorption studies

Background: In dye-based wastewater decontamination, coagulation-flocculation (CF) induced by Luffa cylindrica seed (LCS) was applied. Methods: The effects of parameters (dosage, pH, stirring/settling time) were investigated using one-factor-at-a-time and Box-Behnken jar test which was designed to optimize the removal of color/total suspended solids (CTSS), chemical oxygen demand (COD) and Chromium VI metal. Proximate and instrumental LCS and post-treatment settled sludge characterization, kinetics, mass transfer and CF adsorption study of the process were investigated. Significant findings: LCS's proximate composition revealed high crude protein, while its instrumental characterization identified a network of structures with an active surface and a partial crystalline composition. At pH 2, the removal efficiency of CTSS was 99.2% at 1400 mg/L for 30mins, COD was 90.07% at 1400 mg/L for 30mins and at pH 6 chromium was 98.29% at 1800 mg/L for 15mins, these were reported at optimum conditions. Kinetic parameters; rate constant, K-11, and half-time coagulation, tau(1/2) were determined. The CF adsorption isotherm followed the Freundlich pattern and the kinetic was pseudo-second order. After settling for 300 min, dye removal decreased from the original dye concentration of 1000mgL(-1) to 3mgL(-1) due to the rapid mass transfer process. R-2 was > 0.9 for all the studies, and error indicators reported low values. The high dye-polluted wastewater decontamination potential of bio-coagulant was therefore established. The kinetic, mass transfer and CF adsorption study data obtained may be useful for bio-coagulation system design, a start-up operating time, design control and optimization. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.

Automated summary

The study investigated the application of coagulation-flocculation induced by Luffa cylindrica seed in dye-based wastewater decontamination. The proximate composition of LCS showed high crude protein content, with an active surface and partial crystalline structure identified during instrumental characterization. Optimum conditions led to effective removal of contaminants, with adsorption following Freundlich pattern and rapid mass transfer process observed during settling. The data obtained may have practical implications for system design and optimization in dye-polluted wastewater treatment.