Preparation, characterization and salt-resistance of a coal based super absorbent composite

Potassium humate was extracted from brown coal. A novel super absorbent composite, poly (acrylic acid-co-acrylamide)/potassium humate (PAA-AM/KHA), was prepared by graft polymerization of acrylic acid, acrylamide and coal based potassium humate using N, N'-methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of reaction temperature, degree of neutralization of the poly (acrylic acid) and the amounts of crosslinker, initiator and potassium humate were investigated. Salt resistance tests were also carried out. The composite prepared under optimal conditions had a potassium humate content of 10% and exhibited a water absorption of 770 g/g in distilled water, and 349, 286 and 41 g/g in 0.5 mol/L KCl, MgCl2 and AlCl3 solutions respectively. The results indicate that the salt resistance of PAA-AM/KHA was superior to that of poly (acrylic acid-co-acrylamide) because of the collaborative effect of functional groups of the coal based potassium humate. The PAA-AM/KHA micro powder was characterized by IR spectroscopy and the micrographic surface was characterized by scanning electron microscopy. Introduction of potassium humate into the poly (acrylic acid-co-acrylamide) structure creates a composite more suitable for use as a water-managing material in the renewal of arid and desert environments. The salt resisting property of the composite is improved, production costs are reduced and the growth stimulant effect is still present.