Effect of crystal transformation of hydrolysis products on coagulation performance of iron salt for algae removal

FANG Xin; WAN Jun-li; NIE Xiao-bao; TU Luan-lin; SUN Shi-quan; ZHAO Yu-xin

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China Environmental Science ›› 2026, Vol. 46 ›› Issue (1) : 152-160.

Water Pollution Control

Effect of crystal transformation of hydrolysis products on coagulation performance of iron salt for algae removal

FANG Xin¹, WAN Jun-li^1,2, NIE Xiao-bao^1,2, TU Luan-lin¹, SUN Shi-quan^1,2, ZHAO Yu-xin³

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Abstract

Outbreak of blue-green algae posesa threat todrinking water safety. Coagulation is a key technology for algae removal in waterworks, andiron salt is one of the most commonly used coagulants. To further explore the mechanism of iron salt for removing algae, Microcystis aeruginosa and algal organic matters were selected as the target pollutants. The effect of crystal transformation of the main hydrolysis products on removal efficiency and coagulation process was investigated. The results indicated thatthe transformationof crystalline state, crystalline phase, and crystal form of hydrolysis products were mainly affected by the coagulant dosage and pH value. With the increase of dosage and pH, the main hydrolysis product FeO(OH) was replaced by amorphous Fe(OH)₃(PDF#22-0346), and then converted to Fe₃O₄. Amorphous Fe(OH)₃ finally transformed into quasicrystalFe (OH)₃(PDF#38-0032). The surface characteristics of algal flocs were affected by the crystalline state and crystal form change of hydrolysis products. The maximum S_BET and V_t values of algal flocs were observed at a dosage of 0.7mmolFe/L, which werebeneficial to adsorb algal organic matters andresulted in the optimal treatment efficiency. Within the range of 0.1~0.5mmolFe/L, the crystal transformation of the main hydrolysis products had a more significant effect on algae removal efficiency, particle size and growth rate of algal flocs.

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iron salts / coagulation / hydrolysis products / crystal transformation / algae removal

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FANG Xin, WAN Jun-li, NIE Xiao-bao, TU Luan-lin, SUN Shi-quan, ZHAO Yu-xin. Effect of crystal transformation of hydrolysis products on coagulation performance of iron salt for algae removal[J]. China Environmental Science. 2026, 46(1): 152-160

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