Study On Technology And Mechanism Of Gypsum Board Preparation From The Waste Residue For Cutting Artificial Granites

The waste residue for cutting artificial granites are disposed by stacking and burying,it not only takes up space,but also pollute the environment.In addition,waste acid produced by industry can not be treated effectively.The paper uses artificial stone cutting chips as raw materials,and pure sulfuric acid?98%?instead of waste acid,it synthesizes gypsum powder by acidification and oxidation synthesis,and prepared a building gypsum board with a certain intensity.The results of the research can make use of resources for the two time,solve environmental problems and achieve green production.?1?The analysis shows that the content of toxic and harmful elements in the waste residue for cutting artificial granites is lower than that stipulated in national standard;The total organic carbon content is about 4.66%;The main composition of cutting raw materials is calcite,which can be used as raw material for building gypsum.?2?In the study of the production of gypsum from dilute sulfuric acid acidification the waste residue,the optimum dosage ratio of the waste residue to concentrated sulfuric acid?98%?is 1:0.8,it is lower than the solid to liquid ratio of the theory is 1:0.86;At room temperature,the concentration of dilute sulfuric acid is 50%and stirring 1h at 500r/min speed and after static 4h can synthesize needle-like gypsum powder with particle size d₅₀0 of 11?m,d₉₀ of 56?m and whiteness of 86;The removal rate of total organic carbon was about 5%⁸%during the whole study;The filtrate is transparent due to the hydrolysis and flocculation of Fe³⁺and it can be reused.?3?Hydrogen peroxide has better effect in oxidizing organic matter under acidic conditions?pH?5?,when the amount of hydrogen peroxide is 50kg/t,the removal rate of organic carbon is about 31%;Concentrated sulfuric acid with a solid-liquid ratio of 1:0.7 slowly added to the waste residue,it adds to water with a solid-liquid ratio of 1:3 which is diluted by 50g sulphuric acid?98%?and reacting,stirring 1h at500r/min speed,the removal rate of total organic carbon is 53%and the micromorphology of gypsum powder is mostly needle like structure;With the increase of the concentration of concentrated sulfuric acid,the conversion rate of carbon is greater,the content of organic matter is less.?4?When different solid liquid ratio is used for washing the synthetic gypsum,the solid-liquid ratio is 1:2,and the repeated washing and plaster 5 times can remove12%of the total organic carbon content;Under the optimal conditions,the removal rate of organic carbon reached 65%,and the whiteness of gypsum powder was 65.?5?Through the analysis of TG-DSC,it is found that the beta hemihydrate gypsum powder was dried at 135?by the thickness of 2cm,and 8h was dehydrated to form hemihydrate gypsum.With 0.3%citric acid and 0.5%sodium lignosulfonate,the water requirement of oxidized gypsum powder is reduced from 95%to 83%,and water consumption is reduced by 12%;The prepared gypsum board has a flexural strength of 3.8MPa and a compressive strength of 13MPa.