TITLE:
Application of Cassia fistula Seed Extract as a Natural Coagulant for Small-Scale Gold Mining Effluent Treatment
AUTHORS:
Ishmael Quaicoe, Nikao Adziman Lasidzi, Lyanne Korkor Amartey, Maxwell Bonsu, Solomon Quaicoe
KEYWORDS:
Cassia fistula, Coagulants, Small-Scale Gold Mining (SSGM), Mine Wastewater
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.7,
July
10,
2025
ABSTRACT: Recently, the application of plant-based coagulants in wastewater/effluent treatment has drawn much attention due to their many advantages over chemical agents in terms of biodegradability, toxicity, residual sludge production, and cost. In this study, plant-based extract from Cassia fistula seed (CFSE) was experimentally evaluated for its efficiency in treating wastewater from small-scale gold mining operation (SSGM) as a coagulant. The coagulation tests were conducted in 1 L graduated cylinders following manual homogenisation, with interface height measurements at 0, 5, 10, 15, 20, 25, and 30 min. Particularly, the efficiency of reducing the levels of physicochemical parameters (pH, Turbidity, Total Suspended Solids-TSS, Total Dissolved Solid-TDS, and Electrical conductivity-EC) and the heavy metal ions (Arsenic-As, Cadmium-Cd, Chromium-Cr, Copper-Cu, Iron-Fe, Mercury-Hg) concentrations in the SSGM wastewater was explored in relation to coagulant dosage, settling behaviour and kinetics. The physicochemical parameters were analysed using a Crison pH meter, HACH DR/2000 spectrophotometer, Hydro Test HT 1000, Hanna RODI EC/TDS meter and Crison Conductometer Basic C30 whilst the heavy metal ions concentrations were measured using A Varian AA240FS Fast Sequential Atomic Absorption Spectrometer. The settling behaviour results showed a three-phase settling patterns that aligned with charge neutralisation mechanisms dominant in plant-based coagulants. For physicochemical parameters and heavy metals, a drastic removal/reduction was observed: turbidity (93.4% - 97.7% reduction), TDS (80.4% - 90% reduction), EC (80.3% - 93% reduction), TSS (95.9% - 97.5% reduction), As (45% - 75% removal), Cd (25% - 75% removal), Cr (6.98% - 65.12% removal), Cu (59.35% - 95.65% removal), Fe (19.06% - 53.24%) and Hg (11.54% - 23.08%). The pH of the wastewater also experienced an alkaline shift which influenced the cationic activity of the CFSE. Generally, CFSE demonstrated optimal performance for treating SSGM wastewater at 10 g/L dosage, where peak initial settling rate (3.03 cm/min) and the most compact sludge was obtained. Overall, the findings have demonstrated that CFSE offers a sustainable alternative to chemical coagulants for SSGM effluent treatment, though the results represent preliminary or screening-level efficiency under simulated field conditions.