A study on purification of humic acid (HA) isolated from press mud(PM) was conducted at Organic Farming Research Institute( OFRI), UAS, Raichur during 2017-18 with distilled water as a purifying agent in the place of HCl-HF mixture to purify isolated HA from press mud. The conventional procedure makes use of mineral acids and dialysis step. Standard procedures were used to extract and fractionate HA from press mud. The extracted HA was purified by suspending the HA in 50 ml of distilled water, centrifuged for one hour at an interval of 15 minutes; the supernatant solution was analyzed for K+ , Na+ and Ca + Mg by Flame Photometer and Versanate titration methods, respectively. The suspension left over after centrifugation was purified HA which was oven dried at 40 ºC to a constant weight. Washing of HA for 4 consecutive times (15 min for each washing) reduced the ash (mineral matter) content of the HA to an acceptance level of 2 per cent. This finding was associated with significant decrease in content of K+ , Na+ and Ca + Mg with increasing washing time. This observation also suggests that the distilled water used during the purification process served as Bronsted-Lowry acid thereby donating more H+ which may have replaced some of K + , Na + and Ca + Mg at the exchange sites of the HA. Humic acids isolated from press mud can effectively be purified within one hour using distilled water. | Simple method of purification of humic acid isolated from press mud
