Patents
An improved process for extraction of aluminium sulfate from fly ash which comprises: a) mixing fly ash with sulphuric acid in a ratio of 1:2 to obtain reaction mixture; b) heating the above said reaction mixture at a temperature in the range of 100 to 210°C for a period ranging from 45 to 180 minutes; c) cooling the said reaction mixture; d) adding water to the cooled reaction mixture obtained in step (c) and reheating at a temperature ranging from 100 to 120°C for a period of about 1 to 2 hours; e) setting the un-reacted fly ash by allowing the resultant reaction mixture to stand for a period of about 15 minutes; f) adding hot water and filtering to obtain residue; g) washing the residue obtained in step (f) to make it acid free; h) adding the washings obtained from step (g) to the filtrate; i) reducing the filtrate volume by subjecting to heat till the aluminium sulfate starts to precipite, allowing to cool to room temperature; j) separating the aluminium sulfate formed in step (i) by filtration; k) concentrating the filtrate obtained in step j) and cooling to a temperature of the order of 8°C and maintaining for a time period of about 12 hours to obtain residual aluminium sulfate precipitate; l) separating the aluminium sulfate formed in step (k) by filtration in cold condition; m) washing the aluminium sulfate obtained in steps (j) (I) with alcohol and acetone; n) subjecting the washed aluminium sulfate to drying at a temperature in the range of 50 to 70°C, followed by vacuum desiccation.