Environment
Ramin Mohammadi pour; Hossein Ali Akhlaghi Amiri; Hamed Janani
Abstract
This study evaluates the flocculation performance of six starch-based flocculants—native starch, starch-grafted polyacrylamide (St-g-PAM), anionic starch, cationic starch, and two dual-modified derivatives, anionic starch-grafted polyacrylamide (A-St-g-PAM) and cationic starch-grafted polyacrylamide ...
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This study evaluates the flocculation performance of six starch-based flocculants—native starch, starch-grafted polyacrylamide (St-g-PAM), anionic starch, cationic starch, and two dual-modified derivatives, anionic starch-grafted polyacrylamide (A-St-g-PAM) and cationic starch-grafted polyacrylamide (C-St-g-PAM)—on real iron ore tailings from four industrial sources representing different mining regions of Iran: North-East, West, Central Plateau, and South. The flocculants, previously developed via a straightforward one-step synthesis method, were assessed in terms of settling velocity, supernatant clarity, and zeta potential of flocs under controlled conditions (solid contents: 0.5–4 wt%; dosage: 80 ppm). Experimental results revealed that dual-modified flocculants consistently outperformed other variants: A-St-g-PAM and C-St-g-PAM achieved the highest settling rates (up to 0.82 cm/s at 2 wt.% solids) and produced supernatant turbidity values below 15 NTU, compared to >80 NTU for native starch. Zeta potential measurements confirmed enhanced particle destabilization, with floc surface charges approaching −20 mV after treatment. Given their facile synthesis route, high efficiency, and biodegradability, these dual-functional flocculants emerge as promising candidates for large-scale industrial dewatering. The findings highlight their potential as environmentally friendly substitutes for conventional synthetic flocculants, particularly in water-scarce mining regions where efficient water recovery and sustainable tailings management are urgent priorities.
Patrick MUHIZI
Abstract
Excessive amounts of fluoride present in underground water sources are a major health concern worldwide. This study presents a new way to address the global health issue of high fluoride concentrations in groundwater using the abundantly available and cost-effective adsorbent material activated kaolinite ...
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Excessive amounts of fluoride present in underground water sources are a major health concern worldwide. This study presents a new way to address the global health issue of high fluoride concentrations in groundwater using the abundantly available and cost-effective adsorbent material activated kaolinite clay “WR@KN”. The physical and chemical activation methods are employed to enhance its adsorption capacity. The optimum conditions for fluoride removal are determined through batch adsorption experiments, with a maximum adsorption capacity of 0.745 mg/g at pH 6, a particle size of 10 µm, a mixing speed of 210 rpm, a temperature of 24 °C, an initial fluoride concentration of 5.5 mg/L, a dose of 0.7 g activated WR@KN, and a contact period of 240 minutes. WR@KN successfully removes fluoride ions from 5.5 to 0.28 mg/L. The Langmuir isotherm model is found to be the most suitable for describing the adsorption behavior of fluoride on the WR@KN surface with an R2 of 0.99984. The adsorption kinetic modeling shows that the pseudo-second-order model is the best fit with 0.754 mg/g, indicating that the fluoride adsorption process is chemisorption. The exothermic nature of the fluoride adsorption process is confirmed by a negative value of ΔH° (-77.08). The regenerated WR@KN adsorbent could remove fluoride effectively for the first four cycles but its performance deteriorated in the subsequent cycles. Increasing the ionic strength enhances the fluoride removal efficiency. Overall, the results suggest that the WR@KN adsorbent can be a promising material for cost-effective fluoride removal from groundwater.
