| Superabsorbent polymer(SAP) is a kind of new functional polymeric materials, which can absorb a large amount of water and the absorbed water is hardly removed even under some pressure. Beeause of their excellent properties, superabsorbents have attracted considerable interest and proceeded to research for sciencists and technolohists and been used in many applications such as agriculture, horticulture, feminine napkins, sanitation, medicine and soil improvement.Lignin is renewable, non-toxic and commercially available, which makes lignin utilization avaluable. Nowadays, most lignin applications are based on technical lignins, which are mostly separated during pulping process. Most useful materials and water reseources can be well reused by the application of advanced treatment technology for the wastewater of pulping and papermaking. However a large number of lignin in the wastewater are used as a source of fuel, or discharged without any treatment, which caused consequent heavy waste of resources and severe pollution of environment. So, research on the utilization of technical lignin is very important and significant to treat with the watse water from paper mill and to make full utilazation of natural resource.In this paper, LPAAM is prepared using sodium lignosulfonate(LS-Na), acrylic acid(AA) and acrylamide(AM) as raw materials, kaolin as inorganic filler, potassium peroxydisulfate(KPS) as initiator, N,N'-methylene-bis-acrylamide(NMBA) as cross-linker, by solution polymerization using orthogonal design and saponification reaction. The optimized formula based on the assessment of the absorbencies in distilled water and 0.9%NaCl solution is obtained as follows:m(AM):m(AA)=1:1, m(KPS)=1.0%, m(NMBA)=0.1%, pH=3. Then the saponification reaction based on the above-mentioned optimized formula superabsorbent is used with different NaOH solution at 90℃for 2h. Its absorbencies in distilled water and 0.9% NaCl (mass concentration) aqueous solution are respectively 1003g/g and 89g/g.The relationship between the absorbency of LPAAM and the absorbing time is investigated. The effect of types and concentrations, pH and temperatures of the salt solutions on the balance absorbency is discussed. Through the research of the adsorption of Cu2+ and Zn2+ onto LPAAM, the adsorption kinetics of Cu+ and Zn2+ onto LPAAM can be described as The relationship between the concentrations of metal ions and the adsorption capacities is investigated; the effect of solution pH is explored. The maximum adsorption capacities of Cu+ and Zn+ are respectively 180mg/g and 169mg/g. Comparing LPAAM with LPAAM after adsorption of Cu2+ and Zn2+, the results have shown that some FTIR absorption peaks have changed(the small red shifts of the 1668 cm-1 absorption peak, the small blue shifts of the 1565 cm-1 absorption peak); according to TG, the decomposed temperature has rised and residual weight ratio increases respectively by 3.91% and 3.70%; there are more deepened non-uniform gullies on the surface of LPAAM after adsorption of metal ions, and the surface is built-up densely.Under the conditions of the natural evaporation, the water retention capacity of LPAAM in soil is investigated. The effect of mass of LPAAM, the types of fertilizer solution and the soil on the water retention capacity of the soil is discussed. With the same type of soil, the more the resin is used; the more slowly the water retention capacities of soil has been dropped. However, with the more resin, soil losing water will tend to balance. When the dosage of LPAAM is 0.5%(wt.) of soil, among the single and various mixed fertilizers solution, the effect of the water-retention capacities of three kinds of soil for 10%(wt.) urea and 10% urea/0.1% sodium dihydrogen phosphate(1:1, mass ratio) mixed solution are more than 0.5% potassium chloride and 0.1% sodium dihydrogen phosphate/0.5% potassium chloride mixed solution. |
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