Studies On The Preparation Of Polysaccharide-clay Superabsorbency And Its Water-retention And Slow-release Properties

In order to improve the utilization rates of water and fertilizer in arid regions, inthis thesis, we prepared several types of superabsorbent polymers by frontalpolymerization (FP) and conventional batch polymerization(BP) with acrylic acid(AA), acrylamide (AM), and2-acrylamide-2-methyl propane sulfonic acid (AMPS) asmonomers. Several kinds of clays and polysaccharides are added to the composite.Then we prepared three kinds of slow release fertilizers by different ways. The waterabsorbent ratio, physical properties of soil with samples, and their effects on plantgrowth were investigated. The main conclusions were drawn as followings:(1)P(AM-AMPS)/clay/polysaccharide superabsorbent polymers were synthesizedby BP: The water absorbent ratio reached maximum(209and245g/g) when chitosan(CS) and vermiculite (VMT) contents were10%and30%respectively; The soil waterstable macro-aggregates contents were81.3%and94.2%higher than soil controlgroup when CS and VMT contents were8%and15%respectively, and thewater-resistance abilities were84.2%and78.9%higher than the control group. Thecontest of different kinds of clays and polysaccharides shows: The samples addedwith kaolin and CS have the maximum water absorbent ratios (439and508g/g);Compared with the control group, sample added with tourmaline achieves higher soilwater stable macro-aggregates content (increase by128.4%), mean gain size (increaseby87.1%), water-resistance ability (increase by115.8%), and the growth anddevelopment of grass also be promoted.(2)PAA/clay/sodium carboxymethyl cellulose (CMC) superabsorbentnanocomposites were synthesized by FP: The water absorbent ratios of samples addedwith montmorillonite (MMT) and VMT were643and519g/g respectively, themaximum water holding capacities were511.1and533.1g/kg, total porosities of soilwere61.4and65.0vol%, mean gain sizes were0.32and0.42mm. These indicate thatthe water-holding, porosity and aggregate properties can be improved significantlywith the addition of sample with VMT compared with MMT. The samples obtainedby FP show much better performance in the formation of soil water stablemacro-aggregates, salt resistance and thermal stability than those obtained by BP. Thetotal amount of soil water stable macro-aggregates of FP and BP samples were30.1% and30.1wt%respectively; water-resistance abilities were0.34and0.21; waterabsorbent ratios in1mmol/L NaCl were323and180g/g. The thermal analysis resultshows that the main chain of FP sample ruptured at552oC (20oC higher than BPsample), which was a result of the prominent porous structure of FP sample.(3)P(AA-AM)/VMT/CMC superabsorbent composites were synthesized by FP:Water absorbent ratio reached the maximum (459g/g) with VMT content of25%. TheP(AA-AM)/VMT/CMC/fertilizer controlled release compound fertilizer with thefunction of water retention was prepared by three ways(chemical reaction, adsorption,and coating). The release process in water and soil has been checked: Releasefertilizer prepared by adsorption method has a short release time of6h in water. Thewater absorbent ratios of slow release fertilizers loaded with CO(NH2)2and KH2PO4by FP were539and515g/g, and the release processes last13days and30daysrespectively. However, the total release amount of CO(NH2)2didn’t changesignificantly with the increase of loading amount. And the fertilizer release curve ofCO(NH2)2in soil fits the mathematiclal model Niebergull. P(AA-AM)/VMT/CMC/fertilizer prepared by coating method has a release time of20days.