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Chemical oxidation co-coagulation-flocculation for the flotation wastewater treatment of lead-zinc oxide ore from Lanping mine

Gong Xiang, Guo Xiulan, Li Suqi, Yuan Jiaqiao, Ding Zhan, Yu Anmei, Wen Shuming, Bai Shaojun

Physicochemical Problems of Mineral Processing

2024

Vol. 60, iss. 3

art. no. 189756

The flotation wastewater produced by "lead preferred flotation-zinc flotation" all-open process with aids of mixed depressants and cationic-anionic collectors has a high turbidity and multitude of reagent contaminants, and fails to meet the discharge standards. This study objective is to remove fine solid particles and flotation reagents in this wastewater by chemical oxidation cocoagulation-flocculation process. Results of chemical oxidation tests indicate peroxymonosulfate (PMS) exhibits superior performance on decreasing COD, and the COD remarkably decreases to 71.8 mg・L-1 with 100 mg・L-1 PMS addition after 120 min. Moreover, the combined oxidation of radicals (SO4•- and •OH) are responsible for degradation of flotation reagents (Na2S, DCCH, xanthates and amine) in the wastewater. Results of experimental factors confirm that the turbidity of wastewater decreases significantly from 124796 to 71.4 NTU, and the yield of water reaches above 90% with combined usage of lime (500 mg・L-1) and polyacrylamide (PAM, 50 mg・L-1). Besides, the contents of S, P, N, Zn, Pb and Fe decrease, and meet the discharge standards. Results of zeta potential analysis suggest lime reduces the electrostatic repulsion between particles, and PAM plays a bridge link role between particles, accelerating the precipitation of suspended particle.

The depression mechanism on pyrite in a low-alkaline system with combined depressants : Experiment, HSC, DFT and ToF-SIMS studies

Li Suqi, Yuan Jiaqiao, Ding Zhan, Li Jie, Yu Anmei, Wen Shuming, Bai Shaojun

Physicochemical Problems of Mineral Processing

2023

Vol. 59, iss. 3

art. no. 168454

Depression of pyrite in a low-alkaline system has sparked soaring interests for the multi-metal sulfide minerals flotation recently. This study investigates effects of combined depressants (Ca(ClO)2 and CaO) on pyrite flotation with butyl xanthate (KBX). Micro-flotation experiments indicate that the addition of 200 mg/L combined depressants (a mass ratios of CaO to Ca(ClO) 2 of 2:3) and 1.0×10−3 mol/L KBX at pH 9.5 can effectively depresses the flotation of pyrite, and a minimum pyrite recovery rate of 12.5% is obtained. Basic thermodynamic evaluation results confirm the participation of Ca(ClO) 2 significantly decrease the negative Gibbs free energies of pyrite oxidation reaction. Besides, the calcium species (Ca(OH) 2, Ca2+ and Ca(Cl) 2) will spontaneously transform into CaCO3,and it is the ultimate dominant calcium species in the CO32- system. Density functional theory (DFT) results indicate that CaCO3 can chemically adsorb onto the pyrite surface with an adsorption energy of -671.13 kJ/mol. The O1 and Ca atoms mainly contribute to the bonding process and are responsible for the stable adsorption of CaCO3. ToF-SIMS results provide strong evidence that the combined depressants increase the amount of hydrophilic species and decrease dixanthogen adsorption onto the pyrite surface. The thickness of the whole formed hydrophilic species is approximately 50 nm. Semiquantitative amounts of hydrophilic species follow the order of hydroxy calcium>iron carbonyl>calcium carbonate. Overall, hydrophilic species repulse adsorption of dixanthogen and significantly reduce the flotation performance of pyrite.