Application Of Phosphogypsum Whiskers In Papermaking

At present, our country is a world leader in the production and consumption of paper and paperboard. However, it is insufficiency in raw materials, especially high quality materials and the gap increasing year by year. Fillers added in papermaking can save fibers, reduce production costs and improve some properties of paper. But calcium carbonate and other conventional inorganic fillers added to the pulp will reduce the physical strength of paper. Therefore, it is need to develop new fillers and new technology of adding filler and it will be a long and arduous task for paper industrv.How to use phosphogypsum whiskers fully in papermaking is reasearched in this study. The study is based on the structural properties and characteristics of phosphogypsum whiskers and some comprehensive results which have important theoretical and practical value are obtained.Some physical and chemical properties of phosphogypsum whiskers are studied in this study. For example, whiteness96%. Zeta-7.3mv. conductivity2.52ms, solubility0.33g/100g, length-weighted mean length1.239mm. Infrared spectra show-OH and-SO4exist in the surface of phosphogypsum whiskers.The results show that the amount of phosphogypsum whiskers can reach20～30%when added in the bleached straw pulp and softwood pulp and paper also maintain a high physical strength. For example, when we add30%phosphogypsum whiskers in20°SR softwood pulp, tensile index increased9.46%and tear index, burst index and folding also improved. And when we add30%phosphogypsum whiskers in30°SR bleached straw pulp, tensile, tear and burst index increased11.2%,8.7%and6.4%relatively. Hvdroxyl and high aspect ratio may be the cause of enhancing high physical strength of paper.The results show that phosphogypsum whiskers can still strengthen paper in the case of storage often days. In the case of storage of about twenty days, strength index of paper added phosphogypsum whiskers is essentially related to the blank. Storage time of phosphogypsum whiskers shoud be minimized if conditions allow it. Meanwhile, under the premise of phosphogypsum whiskers distributed fully during the experiment, time of distribution also should be minimized.Under the favorable treatment, phosphogypsum whiskers can help to accelerate the speed of filtration. Phosphogypsum Whiskers added30%into paper will not affect the wet strength of sheet.With the number of cycles of whitewater increases, conductivity, TS content, DCS content and COD content increase, pH value decline, and tensile index, burst index increase, tear index decline.The results show that paper will obtain better whiteness, opacity, formation, Z direction tensile and surface strength and so on when phosphogypsum whiskers added into the paper in the case of suitable amount.In the application process, we need to solve the solubility problem. The results also show that paper will obtain better results with appropriate modification process.In short, the use of phosphogypsum whisker to be filled can be a partial substitute of wood, straw pulp for paper, can greatly reduce production costs and pulp pollution index, the most important thing is that phosphogypsum whisker is good for the enhancement of the paper.