Optimization Extraction of Scandium from Scandium Concentrate with Titanium Dioxide Wastewater by Response Surface Methodology

Scandium concentrate and titanium dioxide wastewater (TDWW) all belong to waste, especially TDWW belongs to hazardous waste, it is urgent to find a more efficient and safer treatment method to deal with them, and both waste acid and waste ore contain scandium. The use of waste acid as a leaching agent can achieve the synergistic recovery effect of scandium. First, the leaching temperature, time, and liquid–solid ratio are found to be significant factors through single-factor tests. Then, the test program is designed by using the Box Behnken unit of Design Expert software to explore the relationship between each factor including leaching temperature (℃), leaching time (h), and liquid-to-solid ratio (mL/g). The results show that the interaction between leaching time and liquid–solid ratio was the strongest. The second-order regression model equation generated by the software can well predict the leaching effect of scandium. The scandium leaching efficiency reaches 85.30%, and the scandium content in the leaching residue decreases to 10.24 g/t under the optimal conditions: leaching temperature of 70 ℃, leaching time of 2.0 h, and liquid–solid ratio 8.7 mL/g. The finite element analysis is to simulate the mineral roasting process and the temperature field changes are always present.