N, P and K adsorption and desorption characteristics of humic acids made from the airslake-coal

N, P and K adsorption and desorption characteristics of humic acids, which were made from the efflorescent coal at different pH values were studied in this paper. The major results were summarized as follows: 1) The N, P and K adsorption and desorption amounts of humic acids showed a rising tendency along with the increase of initial concentration of N, P and K at different pH levels (from 4 to 8), but the desorption ratios of them all declined. 2) The characteristics of adsorption and desorption of humic acids on nitrogen, phosphorus, and potassium were variable at different pH, among which N adsorption and desorption capacity became larger particularly under the alkali condition, while under the acid condition, the P adsorption and desorption capacity increased, and K adsorption and desorption of humic acids was easier in the neutral solution. 3) The isothermal adsorption of humic acid on N, P and K could be fitted using Linear, Langmuir, and Frendlich equations with correlation coefficient being significant, among which Frendlich equation was the best.