Study On Preparation Of Exterior Wall Coatings By Paper Mill Sludge

Paper mill sludge is a kind of solid waste produced by papermaking enterprises in wastewater treatment process.It has the characteristics of high moisture content,complex composition,large output and difficult handling.The disposal cost of sludge from papermaking enterprises accounts for 50% to 60% of the total cost of wastewater treatment,which is a cost burden for enterprises.The traditional treatment methods of paper sludge mainly include circulating fluidized bed incineration,sanitary landfilling and ocean abandonment,etc.However,these methods generally have the problems of secondary pollution of the environment,land occupation,and high cost.Faced with the current serious environmental pollution and ecosystem degradation and other serious situation,and with the vigorous promotion of ecological civilization construction,domestic and foreign scholars pay more and more attention to the stabilization,harmlessness,reduction and resource disposal of papermaking sludge.This paper aims at the comprehensive utilization of paper sludge,and puts forward its potential application direction for resource utilization in building exterior wall coating.First of all,the feasibility of using biochemical sludge(OCC biochemical sludge)produced by the wastewater treatment of waste paperboard corrugated paperboard in the preparation of exterior wall coatings was studied.The phase analysis results of OCC biochemical sludge showed that the main components of sludge were calcium carbonate,gypsum,calcium magnesium aluminosilicate,calcium silicate,quartz and dolomite minerals.The composition is basically the same as the pigment filler used in architectural coatings.This feature provides a material basis for the preparation of architectural coatings using paper sludge as a filler.The main raw material quality ratio for preparing the coatings can be expressed as follows: biochemical sludge is 27.78 wt%,polyacrylic acid 505 latex is 16.67 wt%,sodium carboxymethyl cellulose is 0.67 wt%,deionized water is 54.88 wt%.The coatings was tested and the result was that coating in the container state(qualified),construction(qualified),coating appearance(normal),water resistance(normal),drying time(1.03 h),adhesion(grade 0)and resistance to artificial weathering(? 300 h)were in line with GB/T 9755-2014 standard requirements,and the hardness(4 H)of the coating film presented an excellent performance.Studies have shown that OCC biochemical sludge in the preparation of exterior paint has good potential applications.Secondly,the basic formula of OCC biochemical sludge exterior coating was optimized.The optimal technological parameters were: the amount of pure water was 54.37%(wt%),polyacrylic acid 505 latex 16.43%(wt%),sludge 27.38%(wt%),carboxymethyl cellulose(CMC)dosage 0.38%(wt%),ethylene glycol 0.98%(wt%),203 leveling agent 0.09%(wt%),SPA-202 defoamer 0.37%(wt%).In addition to water permeability,results showed that the quality of target product met the standard of GB/T 9755-2014 on the type ? exterior paint requirements.OCC biosolids are weakly basic and hydrophilic,and do not require p H modifiers and wetting agents to be added to the aqueous coating.Dispersants also make the coating alkaline and provide good compatibility with other materials.Then,the study was carried out on improving the water permeability of the OCC biochemical sludge exterior wall coatings.The effects of addition of paraffin emulsion,antioxidant agent,alkyl ketene dimer(AKD),acrylate emulsion,sericite powder and prolonging the stirring time on the water permeability of the sludge coatings were studied.The results showed that in the sludge coating system,the amount of the waterproofing agent was 3.03%,the paraffin emulsion was 1.19%,the polyacrylic acid 505 latex was 22.70%,the sericite powder was 3.79%,and the stirring time was 40 min.The water permeability was 0.4 mL/24 h,in line with GB/T 9755-2014 in the permeability requirements;AKD emulsion can effectively reduce the film water absorption,but the compatibility with the coating system is poor,not suitable as a waterproof component used in the coating system.Appropriate extension of paint time,can reduce the sludge particles in the diameter of the coating so that the coating is more closely to improve the paint resistance to water permeability;The surface of the sludge coating has a papillary structure similar to that of the lotus leaf,which is superior to the commercially available paint in the experiment.Finally,the exploratory study of municipal sludge on the OCC biochemical sludge exterior wall coating performance was carried out.The total quality of the wastewater sludge in the coating system was maintained,and municipal sludge was gradually added according to a certain proportion to test its properties such as thixotropy index,contact angle,surface tension,hardness,viscosity,water resistance,alkali resistance and adhesion.The results showed that the addition of municipal sludge could reduce the thixotropic index,the contact angle,the surface tension and the hardness of the coating,but improve the viscosity of the coating system.However,the water resistance,alkali resistance and adhesion of the coating had no obvious adverse effects.Municipal sludge on the coating performance has its advantages and disadvantages,and by controlling the amount of addition and avoiding weaknesses,it can have application potential in the preparation of exterior wall coatings.