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Optimization of the microstructure of carbonized lime mud by sodium polyacrylate

Abstract Lime mud (LM) is a by-product originated from the causticization process of papermaking industry. Microscopic structural changes of LM in carbonization process lead to defects on its performance. Regulating the growth of calcium carbonate obtained from the carbonization process and preventing its influence on the surface microstructure of LM has become the key to achieve the self-digestion of this solid waste. In this study, microscopic structural changes of LM co-carbonized with sodium polyacrylate (PAAS) were investigated. The results showed that, compared with traditional carbonation, the microstructure of LM co-carbonized with PAAS was changed remarkably. The newly calcium carbonate formed in the carbonization process would be solidified and coated on the LM surface. Then LM co-carbonized with PAAS would have a smaller specific surface area, pore volume and pore size, which significantly improved its application performance when it was used as paper filler. In addition, a potential technique for improving the surface microstructure of calcium carbonate particle was proposed.