Study On Radiation Modification Of Lignin And Its Application

Sodium lignosulfonate(LS)is a by-product from industrial papermaking wastewater treated by sulfite,which has large output,low utilization degree and utilization efficiency.LS has enormous potential of taking part in a chemical reaction due to its rich groups.Hence,we here aimed to modify LS using radiation technology,exploring the value of the application radiation-modified LS products.The major work can be summarized as follows:the modification feasibility of LS through γ-rays irradiation;the synthesis and water absorption of LS/CMC polymer prepared by modified LS through γ-rays irradiation;the synthesis and comprehensive flocculation performance of LS-AM-DMC copolymer prepared by modified LS through γ-rays irradiation.1、Purification and radiation modification of LS through γ-rays irradiation(1)The ash content of LS was significantly reduced and lignin content was significantly increased by "alkali-solution and acid-isolation" refining process,which changed from lump to porous granular.The "alkali-solution and acid-isolation" refining process can create better conditions for LS to participate in chemical reaction.(2)The thermal stability decreased and there were no significant changes in chemical structures after γ-rays irradiation within 200 kGy absorbed dose.The new radical was presented.Meanwhile,with the increase of the absorbed dose,the concentration of free radicals was positively correlated when the absorbed dose below 100 kGy.2、Preparation and water absorption performance of LS/CMC(1)LS/CMC was made from LS and sodium carboxymethyl cellulose(CMC)through γ-rays irradiation,the water absorption rates were used as indicators,the optimum technological conditions were as follows:at room temperature,adding 20 g CMC and 1 g LS to 100 g water,and the absorbed dose is 15 kGy with the radiation dose rate of 5 kGy/h.The liquid absorption ratio of LS/CMC can reach 316.1 g/g(deionized water),89.9 g/g(0.2 mol/L NaCl solution).In conclusion,LS/CMC meets the basic requirements of NY886-2010 for agricultural and forestry water retaining agents:100-700 g/g of water absorption ratio and more than 30 g/g of salt water absorption ratio.(2)The LS/CMC showed honeycomb structures with well-developed pores,and pore size increased with the increase of LS dosage.Due to moisture volatilization and weightlessness,there was no degradation or decomposition within 200℃,exhibiting better thermal stability.Exactly,after UV irradiation for 15 days,the water absorption did not decrease much and the water retention capacity increased with the increase of LS dosage.3、Preparation and flocculation performance of LS-AM-DMC(1)LS-AM-DMC copolymer were prepared by co-radiation grafting copolymerization of LS,acrylamide(AM)and methyl acryloxyethyl trimethyl ammonium chloride(DMC)monomers under y-rays irradiation,taking the grafting efficiency and degree of grafting as the datum,the optimized technological conditions are as follows:1 wt%LS,2 wt%AM,the monomer ratio of DMC:AM was 3:1 and the absorbed dose was 10 kGy with the radiation dose rate of 5 kGy/h,the best grafting efficiency and degree of grafting were 84.52%and 301.78%respectively.(2)The prepared LS-AM-DMC copolymers had a rough surface;the initial decomposition temperature is 27.1℃ higher than that of LS;the maximum water solubility is 98.96%,and the lowest Zeta potential value is 35.4mV,which are better than the commercial PAM flocculant.(3)When the dosage was 2 mg/L,kaolin suspension with pH=3.1 and treated with LS-AM-DMC3 flocculation solution,the maximum transmission of the supernatant after treatment is 96.26%,which was higher than those of PAC flocculant(86.66%)and PAM flocculant(92.27%)under the same conditions.(4)With 200 mg/L dosage of LS-AM-DMC3 flocculation solution was used to treat methyl blue dye wastewater with initial concentration of 60 mg/L and pH value of 5.6,the maximum decolorization rate was 87.21%,which was higher than PAC flocculant(maximum decolorization rate 70.12%)and PAM flocculant(maximum decolorization rate 74.35%)under the same conditions.(5)With 25 mg/L dosage of LS-AM-DMC3 flocculation solution was used to treat the sewage sludge with pH value of 7.1,the lowest cake moisture content was 71.54%,and the lowest specific resistance of sludge was 2.01 ×1011 m/Kg.They were lower than PAC flocculant(the lowest cake moisture content was 89.36%,and the lowest specific resistance of sludge was 2.56×1011 m/Kg)and PAM flocculant(the lowest cake moisture content was 79.98%,and the lowest specific resistance of sludge was 4.02×1011 m/Kg)under the same conditions.