Selection of Collectors for Silica Removal by Reverse Flotation of Phosphate Ore for Mines
The collector selection for mines from shall comprehensively consider silica‑removal efficiency, phosphorus loss rate, reagent cost and process adaptability. Coco diamine is recommended as the first‑choice reagent, followed by C10 ether‑amine. Blended systems of amine‑ethers and amine‑oxides can also be explored. Detailed analysis is shown below:
1. Fatty‑amine‑based Collectors: Coco Diamine as the First Choice
Silica‑removal Performance
Coco diamine delivers excellent silica‑removal capacity at low reagent dosages (0.4‑0.8 kg/t), with collecting capacity far exceeding n‑octylamine, dodecylamine, coco amine and isotridecylamine. For example, at a dosage of 0.6 kg/t, its silica removal rate reaches 22.80 %; when the dosage rises to 0.9 kg/t, the silica removal rate increases to 51.5 %.
Phosphorus Loss Rate
Coco diamine features low phosphorus loss rate. When the silica removal rate hits 51.5 %, its phosphorus loss coefficient is merely 0.40, which indicates that it can well constrain phosphorus loss while realizing efficient silica removal. By contrast, dodecylamine, coco amine and n‑octylamine bring high phosphorus loss. Although isotridecylamine has the lowest phosphorus loss rate, its silica‑removal capacity is weak.
Application Scenarios
It is suitable for phosphate ore with high silicon content and fine dissemination grain size, especially for technological processes operated at ambient temperature with high requirements for phosphorus recovery rate.
2. Ether‑amine‑based Collectors: C10 Ether‑amine with Favorable Comprehensive Performance
Silica‑removal Performance
C10 ether‑amine shows stronger collecting capacity for silicate minerals than isodecyl ether‑amine. Especially under relatively high reagent dosages (>0.3 kg/t), its silica removal rate is obviously higher than that of isodecyl ether‑amine. For instance, at a dosage of 0.75 kg/t, the silica removal rate of C10 ether‑amine can exceed 60 %, while isodecyl ether‑amine has a phosphorus loss rate as high as 35 %.
Phosphorus Loss Rate
C10 ether‑amine has a lower phosphorus loss rate than isodecyl ether‑amine, and its moderate foam stability facilitates flotation‑process control. Though isodecyl ether‑amine presents slightly better silica‑removal performance at low dosages, excessive phosphorus loss at high dosages limits its practical application.
Application Scenarios
It is applicable to silico‑calcareous composite phosphate ore. Reagent dosage needs adjustment to balance silica‑removal rate and phosphorus recovery rate.
3. Amine‑ethers and Amine‑oxides: Great Potential for Blended Systems
Amine‑ethers
Coco‑amine polyoxyethylene‑ether has stronger collecting capacity for silicate minerals than dodecyl‑amine polyoxyethylene‑ether, and causes lower P₂O₅ loss in flotation tailings. Nevertheless, amine‑ether reagents generally have poor biodegradability, and their performance needs improvement via blending.
Amine‑oxides
Cocamidopropyl amine‑oxide exhibits inferior flotation performance compared with n‑octylamine and high P₂O₅ loss in tailings. Currently it shall not be used alone as a silica‑removal collector, but can serve as a blending component to optimize reagent performance.
Blending Recommendations
Blending amine‑ethers (e.g. coco‑amine polyoxyethylene‑ether) with amine‑oxides (e.g. cocamidopropyl amine‑oxide) can improve reagent solubility and selectivity and reduce phosphorus loss rate. For example, by adjusting blending ratios, the silica removal rate can go above 45 %, with phosphorus loss rate controlled within 20 %.
4. Decision‑making Framework for Reagent Selection
Prefer coco diamine
Coco diamine is the optimal option when high‑efficiency silica removal and controllable phosphorus loss are required. It is especially fit for phosphate ore with high silicon content and fine dissemination grain size.
Secondary choice: C10 ether‑amine
For silico‑calcareous composite phosphate ore, C10 ether‑amine can achieve the balance between silica‑removal rate and phosphorus recovery rate through dosage adjustment. Strict dosage control is required to avoid excessive phosphorus loss.
Explore blended reagent systems
For complex refractory phosphate ore, blending amine‑ethers with amine‑oxides can be tried. Alternatively, novel collectors can be developed by introducing other functional groups such as ester groups and amide groups, to further boost silica‑removal performance and mitigate environmental impacts.