Behaviour of partially soluble humic acids in aqueous suspension

Solubility and dissociation of four various humic samples, including IHSS standard, in water are studied in this work. Obtained experimental data are compared with hypothesis of partial solubility of humic acids in aqueous solutions developed in our previous work. It was proved experimentally that behaviour of all used humic samples agrees with the multi-step mechanism of solid humic acids interaction with water, including partial equilibrium dissolution as well as direct equilibrium dissociation from the solid state. Experimental data further demonstrated that regardless the common mechanism, solubility and dissociation degree of various humic samples may be very different and can be estimated using parameters of model based on the proposed mechanism.