Rui Cui

The efficient solid-liquid separation of fine-particle slurries is a significant challenge in mineral processing. In this study, the influence of centrifugal flow conditions and flocculation parameters on fine particle recovery was systematically investigated using cationic polyacrylamide (CPAM) and a multi-stage centrifugal cyclosizer. Static flocculation–sedimentation experiments, centrifugal classification tests, and response surface methodology were combined to evaluate recovery performance. The results showed that within a certain range, the larger the flocculant molecular weight and dosage, the better the static flocculation sedimentation performance, while appropriate centrifugal flow conditions further enhanced fine particle recovery. Response surface experiments indicated that the cyclosizer flow rate exerted the most significant influence on recovery, followed by polymer molecular weight and dosage, with a significant interaction observed between flow rate and polymer dosage. Additionally, microscopic observation and numerical simulation of the cyclosizer were combined to show a method to express the shear resistance strength of floccules using the characteristics of the flow field. In the flocculation hydrocyclone validation experiments, the addition of PAM at a dosage of 70 g/t resulted in a 2.85% increase in underflow concentration and an 8.34% improvement in yield compared with the non-PAM condition. These results indicate that centrifugal separation equipment can regulate floc stability and recovery by altering the shear rate and centrifugal force within the flow field. Therefore, achieving an appropriate balance between flow rate and flocculation intensity is essential for enhancing underflow yield.

In this study, sodium polyacrylate (PAAS) and ultrafiltration membranes were used to extract and separate Cu²⁺ and Ni²⁺ ions from electroplating wastewater. The effects of pH, the P/M ratio (mass ratio of sodium polyacrylate to metal ions), tartaric acid, and sodium citrate on the complexation of Cu²⁺ and Ni²⁺ by sodium polyacrylate were investigated. The retention of Cu²⁺ and Ni²⁺ by PAAS in single metal solutions with a P/M ratio = 4 and pH = 5 differed by 45.36%. When the complexation system of PAAS with a single metal contained tartaric acid and sodium citrate, the retention of PAAS for Cu²⁺ and Ni²⁺ increased to 80.36% and 58.84%. PAAS retention for Ni²⁺ decreased, but retention for Cu²⁺ remained the same. All the results indicated that there was competition between tartaric acid, sodium citrate, and PAAS for the adsorption of Cu²⁺ and Ni²⁺. Some of the Ni²⁺ complexed with PAAS were detached from PAAS complexed by tartaric acid and sodium citrate and permeated through the membrane pores, while the Cu²⁺ complexed with PAAS was not complexed by tartaric acid and sodium citrate and could not permeate through the membrane pores. Therefore, this study helps to provide a theoretical basis for the separation of Cu²⁺ and Ni²⁺ in electroplating wastewater.

In order to separate fluorite and calcite inhibited in tungsten tailings, the effect and mechanism of using ultrasonic external field activation to separate fluorite and calcite inhibited by sodium hexametaphosphate in a sodium oleate system were investigated. After pretreatment with an ultrasonic external field with a frequency of 40 kHz and sound intensity of 0.56, 0.50 and 0.40 W/cm², the flotation recovery of calcite could be increased from 16.08% to about 80%, while the flotation recovery of fluorite was only increased from 7.5% to about 20%, with a difference of 60% between the two flotation recoveries, and the larger the sound intensity, the shorter the pretreatment time and the smaller the ultrasonic input energy. The contact angle of the calcite surface increased, sodium oleate adsorption increased, and zeta potential decreased after ultrasonic pretreatment, while the contact angle, sodium oleate adsorption, and zeta potential of fluorite surface were less changed. The results of heat of adsorption and XPS measurements showed that more heat was released from the interaction between sodium hexametaphosphate and fluorite, and the Ca2p peaks on the surface of fluorite were shifted to a greater extent after the interaction, which inferred that the adsorption of fluorite and sodium hexametaphosphate was relatively easier and stronger. It is presumed that the ultrasonic pretreatment can bring the mineral surface to different degrees of desorption according to the adsorption strength of sodium hexametaphosphate, exposing Ca²⁺ active sites for sodium oleate adsorption, while expanding the floatability difference between fluorite and calcite.