Study On The Adsorption And Mechanism Of ACS For Calcium In Wet-end System

In the paper-making industry, mental ions such as calcium accumulated in wet-end system by the water recycle degree increasing. It influenced the runnability of paper machine and the characters of paper. In this paper, it was researched that the adsorption, ion exchange and mechanism happened between mental ions and fiber, anonic trash with carboxyl groups.It was meaningful for prevention of mental ions and enhancing the degree of white water recycle in paper making industry.It was invested that the chemincal adsorption of calcium on the bleached reed, hardwood and softwood kraft pulp happened. Their adsorption capacities of calcium were 0.024, 0.016 and 0.0084mmol/g respectively at pH7.5±0.3,temperature25±1℃. The equilibrium data have been found to fit the Langmuir adsorption isotherms. It revealed that the interaction between pulp and calcium were monolayer dsorption. The adsorption capacities increased with increasing pH and became almost constant when pH was above 7.0.The effect of temperature was not significant.Calcium soap was investigated by turbidity of the solution. Calcium and dissolved rosin were must to the formation of calcium soap. The concentration of both was closely related to the calcium soap. The content of calcium soap reached a constant within 10 min. There was more calcium soap in higher temperature indicating endothermic nature of the process.The ACS, a modified natural polymer with branch, was used for removal of calcium from aqueous solution. Its DS of carboxymethyl groups was 0.5687, and cationic groups were 0.02013. It adsorbed calcium and resided on fiber with its cationic charge. The adsorption capacities reached a state of equilibrium within 90 min. The equilibrium data have been found to fit both the Langmuir and Freundlich adsorption isotherms. The adsorption capacities increased with increasing pH, inintial concentration and the dose of ACS. The adsorption capacities became almost constant when pH was above 6.5. There was an optimum dose of ACS for removal of calcium.ACS reduced the negative effects which caused by calcium on CPAM and AKD with Poly-DADMAC. When the condition was: pH7.5, CS:1.0%, AKD:0.2%, CPAM:0.025%, [Ca²⁺]:18.746mmol/L, poly-DADMAC:0.075%, the drainage time shorted 23%, turbidity reduced 26% NTU and sizing increased 23% at ACS:0.2% .In this paper, the effect of various operational variables, viz., solution pH, initial concentration of calcium ion, the dose of ACS, temperature on calcium soap had been studied. ACS could reduce the content of calcium soap by removal calcium.