Removal Of Calcium Ions From Waste Paper Pulping And Papermaking Wastewater

In recent years,the technology of paper recycling papermaking has been innovated continuously,and recycled paper has gradually become an important pillar in the field of papermaking.However,due to the complex composition of waste paper and the large amount of calcium additives,high Ca2+ wastewater is generated.As a result,anaerobic/aerobic biological treatment system becomes calcified seriously and the membrane fouling in membrane separation technology is difficult problems in the closed circulation and "zero emissions" of waste water.This paper mainly study the calcium treatment of anaerobic influent and secondary sedimentation tank effluent during the wastewater treatment process of paperpulping and papermaking enterprise,This research contents are divided into the following three parts:Part I:In order to prevent the anaerobic granular sludge calcification,this study combined chemical precipitation method and anaerobic reflux aeration were used to anaerobic wastewater decalcification.By adding Ca(OH)2 solution,the pH value was adjusted to 10 and the anaerobic influent and effluent ratio was controlled to be 1:3.After 3 h of aeration,the content of Ca2+ reached about 200 mg/L of the standard of industrial recycling water.FT-IR and XRD analysis showed that the main component of the precipitate was the calcium carbonate precipitation of dense calcite crystal.Part ?:Using kaolin as raw material,the optimum synthesis conditions of 4A molecular sieve hydrothermal method were studied:after 800? calcination 2.5 h get metakaolin;Quaternization material than for:Tn(SiO2)/n(Al2O3)is 2.0,n(Na2O)/n(SiO2)is 2.6,n(H2O)/n(Na2O)is 55,at 50? alkalify 6 h,110?crystallization reaction 4 h,the synthesis of molecular sieves Ca2+ adsorption unit reached to 37.6 mg/g.FT-IK XRD and SEM etc,showed that the high purity of the synthetic material,and it seems to the characteristic of the standard 4A molecular sieve.Part ?:In order to deal with the problem of film fouling in membrane separation technology,the application of 4A molecular sieves to decalcification of effluent from secondary sedimentation tank of pulp and papermaking wastewater was studied.when the Ca2+ concentration of 220 mg/L,the reaction temperature 45?,pH of 8,the usage of 4A molecular sieves is 5 g/L,the conditions of ultrasonic power of 100 W reinforced adsorption 100 min,Ca2+removal rate can reach 86.4%,Ca2+ concentration down to about 30 mg/L.The results showed that the adsorption process of the synthesized 4A molecular sieve to the Ca2+ in wastewater was accordance with both Langmuir and Freundlich isothermal adsorption models and Pseudo second-order kinetic models.