Preparation And Properties Of Superabsorbent Based On Wheat Straw/Bentonite

Superabsorbent is a kind of polymer absorbent materials. Their superior water absorbency and water retention make them applied widely in many fields. In order to realize the resourceful utilization of wheat straw, a novel superabsorbent resin (SAR) was prepared by the solution polymerization of pretreatment wheat straw (WS), acrylic acid (AA), acrylamide (AM). In order to improve the water absorption, salt resistance and gel strength of SAR, novel SAR were prepared by the solution polymerization of pretreatment wheat straw (WS), acrylic acid (AA), acrylamide (AM) reacting with sodium bentonite and modified bentonite, respectively. The dosage of cross-linking agent and initator, mass ratio of monomer, neutralization degree of AA, the dosage of WS and bentonite, which influenced the water absorption capacity of SAR were investigated. FT-IR, TGA, XRD and SEM were conducted to characterize SAR. The water absorbency capacity, water retention, heat-resistant capacity and salt resistance of SAR were researched and compared.The result was obtained as follows:The best synthesis condition of SAR without bentonite was:the best weight rate of the cross-linker and the initiator were0.10%and1.5%, the most appropriate ratio of monomers was m (AA):m (AM)=3:1, the most suitable neutralization degree of AA was80%, the mass of WS was1.0g, The water absorbency in distilled water and0.9%NaCl solution was151.5g·g-1and20.7g·g-1, respectively. The best synthesis condition of SAR with sodium bentonite was:the best weight rate of the cross-linker and the initiator were0.08%and1.5%, the most appropriate ratio of monomers was m (AA):m (AM)=3:1, the most suitable neutralization degree of AA was80%, the mass of WS was1.0g, the best weight rate of sodium bentonite was0.30%. The water absorbency in distilled water and0.9%NaCl solution was173.0g·g-1and22.8g·g-1, respectively. The best synthesis condition of SAR with modified bentonite was:the best weight rate of the cross-linker and the initiator were0.05%and1.5%, the most appropriate ratio of monomers was m (AA): m (AM)=3:1, the most suitable neutralization degree of AA was80%, the mass of WS was1.0g, the best weight rate of modified bentonite was0.20%. The water absorbency in distilled water and0.9%NaCl solution was195.7g·g-1and24.2g·g-1, respectively.FT-IR proved that SAR was synthesized successfully; TGA displayed that the heat-resistance capacity of SAR with bentonite was more excellent than SAR without bentonite; XRD indicated that the bentonite was exfoliated and dispersed in the polymer. SEM showed that the amount of wrinkle on the surface of SAR was in proportion to the water absorbency of SAR.Comparing with the SAR without bentonite, the water absorbency and repeating water absorbency of SAR with bentonite was improved obviously:the water absorbency of SAR with sodium bentonite improved14.2%and10.1%in distilled water and0.9%NaCl solution, the water absorbency after repeating5times improved13.3%and13.7%; the water absorbency of SAR with modified bentonite improved29.2%and16.9%in distilled water and0.9%NaCl solution, the water absorbency after repeating5times improved18.2%and19.0%; The experimental results of retention capacity showed that the water retention capacity of SAR with bentonite increased at room temperature,50℃,70℃and90℃, moreover, the SAR with modified bentonite was more excellent than the SAR with sodium bentonite.The experimental results of gel strength turned out that the gel strength of SAR with bentonite after absorbing and repeating absorbing improved, moreover, the SAR with modified bentonite was more excellent than the SAR with sodium bentonite.