Challenges and mitigation techniques in selective flocculation of iron oxide fines: A data-driven critical review

초록

Rising global demand for iron has intensified efforts to valorize iron oxide fines and establish selective flocculation as a critical beneficiation route. Selective flocculation exploits mineral surface chemistry differences to selectively flocculate the target mineral. This review adopts a data-driven literature analysis approach to systematically evaluate studies published between 1969 and 2025 on the selective flocculation of iron oxide fines, integrating surface speciation modeling to elucidate interfacial interactions and focusing on reagent systems, operating conditions, performance metrics, and underlying mechanisms. Sodium silicate, sodium hexametaphosphate, and sodium tripolyphosphate are the most widely applied dispersants, whereas causticized starches and polyacrylamides (PAMs) are the dominant flocculants. Starch selectivity increases with amylopectin content, whereas moderately carboxylated anionic PAMs outperform both weakly and highly anionic PAMs. Alternative flocculants, including xanthan gum, guar gum, carboxymethyl cellulose, and polyacrylic acid, have also demonstrated potential for selective flocculation of iron oxide fines. Typical operating conditions cluster around a mean pH of 9.8, particle size of ∼28 µm, and pulp density of ∼2.5 wt%. Performance evaluations using the iron enrichment ratio (ER) and separation efficiency (SE) define three regimes: region A (ER, 1.1–1.35; SE, 38.9–68.8%), region B (ER, 1.59–1.92; SE, 44.5–86.2%), and region C (ER, 1.22–2.0; SE, 90–93.7%), reflecting distinct reagent−process combinations. Mechanistic studies show that flocculant adsorption onto iron oxides is dominated by chemical and hydrogen bonding, whereas interactions with silicate gangue are primarily governed by weak hydrogen bonding. Enhanced ER and SE can be achieved through moderate agitation, controlled pulp density, multistage flocculation−desliming using moderately anionic flocculants followed by washing the concentrate with water conditioned with a mild dispersant.

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