Optimization Strategies of Collectors for Silica Removal by Reverse Flotation of Phosphate Ore
The optimization strategies for the process at are presented as follows:
Prioritize coco diamine: Coco diamine exhibits remarkably stronger collecting capacity for siliceous minerals such as quartz compared with other fatty‑amine‑based collectors including dodecylamine and coco amine. At a reagent dosage of 0.6 kg/t, it achieves a silica‑removal rate of 51.5 % with a phosphorus loss rate of merely 8.2 %, and raises the P₂O₅ grade of concentrate to 30.4 %. Its advantages stem from two amino groups and mixed carbon chains (C12‑C16) in its molecules, which strengthen physical adsorption onto silicate minerals and mitigate entrainment of phosphate minerals.
Explore improvements for ether‑amine‑based collectors: Ether‑amines such as C10 ether‑amine gain improved solubility and foaming performance by introducing ether‑oxy groups, and deliver superior collecting capacity and selectivity for silicate minerals over fatty amines. Nevertheless, attention should be paid to their poor biodegradability and the toxicity of synthesis raw‑materials such as acrylonitrile. Molecular‑structure optimization (e.g. insertion of ester groups) can be adopted to boost environmental performance, meanwhile reagent dosage shall be controlled to strike a balance between silica‑removal efficiency and phosphorus loss.
Develop blended systems of amine‑ethers and amine‑oxides: Although amine‑ethers represented by coco‑amine polyoxyethylene‑ether have moderate collecting capacity, they can be blended with amine‑oxides such as cocamidopropyl amine‑oxide to improve reagent solubility and selectivity. For instance, blending coco‑amine polyoxyethylene‑ether with oxidized paraffin soap can realize high‑efficiency silica removal at low dosage and reduce phosphorus loss rate. Gradient tests are required to optimize blending ratios of mixed systems for adaptation to diverse ore properties.
Adjust reagent regimes according to ore characteristics:
High‑siliceous phosphate ore: Adopt coco diamine as the main collector, combined with starch or water glass to depress phosphate minerals, so as to realize efficient silica removal under pH 5.0‑5.5.
Silico‑calcareous composite phosphate ore: Remove partial quartz via direct flotation first, then carry out reverse‑flotation silica‑removal; alternatively, adopt the double‑reverse‑flotation process to eliminate siliceous and carbonate gangue in separate stages.
Fine‑grained disseminated phosphate ore: Add dispersants such as water glass to suppress ore slime, or apply low‑foam collectors (e.g. modified fatty acids) after pre‑desliming to reduce mechanical entrainment.
Optimize process parameters and supporting equipment:
Pulp‑pH control: Reverse‑flotation silica removal is generally performed at pH 5.0‑5.5. Sulfuric acid or phosphoric acid shall be used for adjustment with real‑time pH monitoring.
Grinding fineness: Ensure the ‑200‑mesh fraction accounts for 75 %‑85 % to achieve full mineral liberation and prevent intergrowth particles from entering concentrates.
Flotation time: Determine the optimum duration through flotation‑rate tests to avoid phosphorus loss caused by over‑flotation.
Equipment selection: Adopt high‑efficiency thickeners and ceramic vacuum filters for dewatering, to lower concentrate moisture content below 12 %.
Attach importance to environmental protection and economic benefits:
Reagent cost: The unit cost of single coco diamine reagent is approximately 100 CNY/t, and the cost rises to 120 CNY/t for blended systems. Such extra expenditure can be offset by higher concentrate grade and recovery rate.
Wastewater treatment: Adopt recycled‑water circulation technology to cut water consumption and mitigate environmental impacts from residual reagents.
Green‑reagent development: Research eco‑friendly collectors such as ester‑group‑containing quaternary ammonium salts to enhance biodegradability and reduce adverse ecological impacts.