Synthesis and decoloring properties of sodium humate/poly (N-isopropylacrylamide) hydrogels.

A series of novel sodium humate/poly(N-isopropylacrylamide) (SH/PNIPA) hydrogels were synthesized by solution polymerization. The swelling and decoloring properties of SH/PNIPA hydrogels were also examined. Experiment results show that there exist hydrogen-bonding interactions between SH and PNIPA in the SH/PNIPA hydrogels network, which are not strong enough to disrupt the aggregation of dehydrated PNIPA chains at phase transition temperature, leading to the same volume phase transition temperature as pure PNIPA hydrogel. The adsorption and desorption of methylene blue (MB) for the hydrogels were influenced by temperature, initial MB concentration and SH amount. Low temperature favors the adsorption and desorption of MB. Appropriate SH amount of the hydrogels is crucial for the adsorption and desorption of MB. The maximum adsorption capacity was 10.8 mg MB per gram of SH/PNIPA gel.