Synthesis And Properties Of Waste Edible Fungus Substrate-based Composite Superabsorbent

Superabsorbent polymers in agricultural are known as the fourth kind ofagricultural chemicals after fertilizers, pesticides and plastic films that can beaccepted by farmers. However, they are not widely used in many applications due tothe high cost, the single function of water retention and release, and that the gelstrength is low after swelling. In this paper, using waste edible fungus substrate（WEFS, the substrates of cultivate edible fungus, which consist of corn cobs andsawdust. After growth the edible fungus we can get the waste substrate） as the rawmaterial, mixing the modified WEFS with polymer monomer, a varietyof WMFS-based composite superabsorbent were synthesized by solutionpolymerization using microwave radiation and UV irradiation. And the preparation ofits most synthesis conditions and properties were studied. The major work of thisthesis was showed as follows:1. A novel superabsorbent polymer composite was successfully synthesized fromwaste material cultured Auricularia auricula （WMCAA） and poly （acrylicacid-co-acrylamide）（P（AA-co-AM）） using microwave irradiation at a certainneutralization degree of AA. Optimal synthesis conditions were determined byinvestigating the water absorbency of the superabsorbent composite, The effectsassociated with weight ratios of WMCAA, AM, initiators, cross-linkers to AA as wellas the degree of neutralization of AA were examined. The maximum waterabsorbencies were found to be1548g.g^-1（distilled water） and72g.g^-1g/g （0.9wt%NaCl solution）. The molecular structure characteristics of the superabsorbentcomposite were analyzed by Fourier transform infrared spectroscopy （FTIR）, andscanning electron microscopy （SEM） was used to demonstrate the characteristiccompact and porous structure of the material. Further studies conducted viatransmission electron microscopy （TEM） revealed the formation of a novelinterpenetrating polymer network structure. Thermogravimetry/differential thermal （TG/DTG） analysis demonstrated improved thermal stability in the compositematerial compared to WMCAA. Additionally, high water absorption rates observed inthe polymer during the swelling process indicated first-order kinetics. The waterabsorption and adsorption of the superabsorbent composite were studied in a varietyof fertilizer solutions, revealing an indirect relationship between water absorbingability and fertilizer concentration. Conversely, a direct relationship was observedbetween absorbed fertilizer and fertilizer concentration.2. The waste material cultured pleurotus nebrodensis （WMCPN）/Potassiumpolyacrylate（PAA-K）composite superabsorbent rich in plant nutrient elements K,neutralizing acrylic acid with potassium hydroxide, was synthesized via a certainpower of microwave radiation. The maximum water absorbency of the synthesizedcomposite superabsorbent under the optimal conditions of synthesis was974g.g^-1indistilled water and59g.g^-1in0.9wt%NaCl solution, respectively. The molecularstructure characteristics of the superabsorbent composite were measured by FTIR.The thermal stability of the composite was also analyzed by TG/DTG. SEM was usedto demonstrate the characteristic coarse and porous surface of the material. In addition,the water loss rate was6.2%with centrifuging at6000rpm for60minutes.3. The waste material cultured pleurotus ostreatus （WMCPO）/PAA-K compositesuperabsorbent was synthesized by the same way with two. The maximum waterabsorbencies of the superabsorbent was827g.g^-1in distilled water and87g.g^-1in0.9%NaCl solution, respectively.The water loss rate was only4.3%with centrifugingat6000rpm for60minutes.4. The composite superabsorbent was synthesized by copolymerization of TheWaste material cultured nameko （WMCN）and Sodium polyacrylate（PAA-Na）under UV irradiation, in the presence of dimethoxy-2-phenylacetophenone（BDK） andAPS as initiator. The structure, morphology and thermal stability of the compositesuperabsorbent were analyzed by FTIR, SEM and TG/DTG. The experiment showedthat the maximum water absorbency of the synthesized superabsorbent was1701g.g^-1in distilled water and388g.g^-1in0.9wt%NaCl solution, respectively. Moreover,the swelling process of the composite in distilled water and0.9wt%NaCl solution follows the pseudo-second-order swelling kinetic model. In addition, The waterabsorbency in0.1wt%urea solution was1011g/g, and80%amount of urea diffusedinto the gels. The urea diffusion mechanism follows Fickian diffusion mechanism.The Retention capability of superabsorbent under pressure and heating was alsodetermined, Water retention capability of composite superabsorbent is65%atconstant temperature of60°C for15hours and75%with centrifuging at6000rpm（10954KPa） for60minutes.