This study explored the synthesis of potash alum from disposed aluminum cans for water purification. The effect of the labels on the cans on the yield of alum was also investigated as it is economically beneficial for industry. Single crystals of potash alum were obtained and characterized by powder X-ray diffraction (P-XRD) and Fourier transform infrared (FTIR) spectroscopy. Through a series of jar test experiments, the characterized alum samples were used to purify river water samples. Some of the parameters investigated include; pH, turbidity, total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC) and chemical oxygen demand (COD). The results show that the alum samples were able to reduce the turbidity by 100 % and substantially decrease the TSS, TDS and COD over the five-hour period of study. However, there were slight increases in acidity and EC which could be corrected by other methods