The current study investigated the effects of novel hybrid polyacrylamide polymers as ash (slime) depressants in fine coal flotation to enhance combustible recovery and ash rejection. Coal samples at P80 of approximately 45 um with ~25% ash content were floated in the presence of in-house synthesized hybrid aluminum hydroxide polyacrylamide polymers (Al(OH)3-PAM, or Al-PAM). All flotation experiments were carried out in a 5-L Denver flotation cell. Various influencing factors were examined to optimize the flotation process in the presence of the Al-PAM polymers, including the Al-PAM dosage, Al-PAM conditioning time, impeller rotation speed and pulp pH. Comparative and synergistic studies were also performed using organic polyacrylamide polymers (PAMs), commercial dispersants and Al-PAM/dispersant system. Results showed a significant improvement in both combustible recovery and ash rejection at an Al-PAM dosage of 0.25 mg/L. The maximum combustible recovery obtained, at natural pH, with Al-PAM and Al-PAM/dispersant system was determined to be 70% and 66% at ash content of 7.74% and 7.4%, respectively. Zeta potential values of both the raw coal and concentrate products showed a large shift toward more positive values (from ˉ50 mV to ˉ13 mV), indicating a significant decrease in ash-forming minerals (slimes) when Al-PAM polymers were applied.
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