Beneficiation of iron and aluminium oxides from fly ash at lab scale

• We have separated the part of iron magnetically from fly ash first time in lab.
• Residue of fly-ash was treated with HCl to leach Al & Fe.
• Effects of acid conc., acid quantity & contact time on leaching of Al & Fe have been studied.
• Leachate was precipitated with NH4OH & precipitates were dehydrated to alumina and iron oxide.

During electricity production, the fly ash (FA) is generated from the combustion process and it is a pollutant. Present investigation was carried out for the recovery of iron oxide and alumina from fly ash. The fly ash was subjected to magnetic separation where part of iron oxide was separated. After this the fly ash was leached with hydrochloric acid followed by precipitating the leached liquor with ammonia hydroxide to get hydroxides of alumina and iron which are dehydrated at high temperature (1100 °C) to obtain iron and aluminium oxides as a mixed powder. Leaching of alumina and iron oxides from fly ash with hydrochloric acid, the effects of four parameters viz. acid concentration and acid to fly ash ratio, leaching temperature and time were investigated and optimum conditions were (i) concentration of HCl 6 N, (ii) fly ash (g) to HCl acid (ml) ratio 1:4, (iii) temperature of leaching 107 °C, and (iv) duration of leaching 5 h. The total recoveries of iron oxide and aluminium oxide were 63% and 73%, respectively.