Application Of Protein Recovery From Excess Sludge As Coating Paper Latex

The residual sludge is a solid waste produced in the biological treatment process of urban sewage.The utilization of protein resources extracted from residual sludge can be used to realize reduction and resource utilization of the sludge.The protein recovery from excess sludge,which is a renewable resource,can be applied to foam extinguishing agent,plant nutrient solution,microprotein organic fertilizer and so on.The added value of that products is low.As a biological macromolecule resource,the protein has not been fully utilized.In recent years,the development of biomass green paper chemicals using soybean protein,casein and other protein has become a hot topic in the industry.Making fully utilized of the protein recovery from excess sludge to develop its industrialization and high value utilization can not only promote the sludge reduction and resource utilization,but also develop new raw material resources for the development of green chemicals.In this paper,the raw material is the protein recovery from excess,and the application effect of the unmodified and modified protein by MMA as paper coating binder was studied.In this paper,the initial raw materials were the extracting liquid from industrial protein recovery from excess sludge.The analysis showed that the total organics content of the extracting liquid of protein was 39.53%,and the crude protein content was 27.03%,accounting for 68.38%of the total organics.The extracting liquid of protein is difficult to apply directly to paper coating,because of its deep color and high inorganics content.After purified by ethanol,protein powder was gained and used as raw material for coating latex.The content of crude protein in raw protein powder was 54.55%and the content of organics was 79.28%.The element analysis showed that it contained potassium,sulfur,silicon and other elements.The results of amino acid analysis showed that the protein contained 17 kinds of amino acids,among which the content of glycine was the highest,which was 16.28%.The molecular weight of the protein was mainly 77 kDa and 101 kDa.The pyrolysis temperature of the protein was 263 ? and 384? and the weight loss rate reached 60.60%at 700?.The protein is used for coating latex together with the styrene acrylic latex.The effect of the dosage of the protein binder on the rheological properties of the coating and the performance of the coated paper was examined.When the best proportion of styrene acrylic latex and protein binder is 11.5:0.5,the drying speed of coated paper reaches maximum,which is 0.70 m/s,increased by 12.90%,the transverse tensile strength of coated paper reaches maximum,which is 2.02 kN/m,but the brightness of paper decreases from 79.22%to 78.22%,the smoothness decreases from 68.59 s to 65.10 s,and the contact angle decreases from 72.6 ° to 64.8 °.Therefore,if the dosage of protein latex used in coatings is excessive,it will effect on the properties of paper.When the mass ratio of MMA to the protein was 2.0,the dosage of emulsifier was 5.00%(the mass ratio of emulsifier SDBS to OP-10 was 3:1),and the dosage of initiator APS was 1.00%,the protein was grafted by MMA.The water resistance of the modified protein film increased.When the dosage of the modified protein and the styrene acrylic latex was 2 and 10,respectively,the drying speed of coated paper reaches maximum,which is 0.85 m/s,the longitudinal and transverse tensile strength was 4.57 kN/m and 2.52 kN/m,respectively,the coating paper surface performance was the best,that the smoothness of coating paper reaches maximum,which is 97.09 s,and the roughness of PPS is the smallest,which is 2.44?m.Under the optimum mass ratio,the maximum pyrolysis temperature of the modified protein increased from 384? to 435?,and the thermal stability was improved significantly.The modified protein can partly replace styrene acrylic latex to coating paper.