Method for preparing gypsum cementitious material water reducer by using pulp waste liquid

Abstract

The invention relates to a preparation process for producing a water-reducing agent for gypsum cementitious materials by using sulfite pulp waste liquid as a raw material, comprising the following steps: 1) precipitating lignosulfonate: adding calcium substances into the pulp waste liquid, Carry out alkalization to obtain calcium lignosulfonate precipitate; 2) filter the precipitate, and perform acidification process on the precipitate: through sedimentation and filtration, through acidification process, a purified calcium lignosulfonate solution is obtained; 3) fine purification process: carry out Ultrafiltration and purification; 4) Compound modification process: adding a water reducing agent and compounding the calcium lignosulfonate solution obtained in step 3) to obtain a modified product. The advantages of the present invention are: the present invention effectively solves the waste liquid of pulp and paper industry, is green and environmentally friendly, saves resources, and conforms to the sustainable development strategy; The molecular weight and number average molecular weight are both greatly increased, and the molecular weight distribution is more uniform.

Description

technical field [0001] The invention belongs to the technical field of waste liquid resource utilization and environmental protection engineering, and in particular relates to a preparation process for producing a water reducer for gypsum gelling material by using sulfite pulp waste liquid as a raw material. Background technique [0002] Pulp waste liquid is industrial waste water produced in the production process of pulping and papermaking industry, and this patent especially refers to the waste liquid produced in the process of cooking pulp by acid sulfite method. Its main components are sulfite lignin, various sugars, organic acids, free sulfite, sodium sulfide, etc., and the content of sulfite lignin is 45-55%. salt. [0003] Lignin is a class of complex natural renewable polymers. It is estimated that about 6×10 14 t lignin. Industrial lignin mainly comes from the pulp and paper industry, which separates about 140 million tons of cellulose from plants every year, a...

AI Technical Summary

Problems solved by technology

However, because the concrete and gypsum systems are different, the effect of the water reducing agent is also very different. There are mainly the following problems: (1) The water reducing rate is not high. When the dosage is 0.7%, the polycarboxylate high-efficiency water reducing agent The water reducing rate is 11.3%, and the water reducing rate of melamine resin water reducing agent and sulfamate water reducing agent is less than 10%. (2) The water reducing rate of naphthalene-based water reducing agent is slightly better, but the bleeding phenomenon is very serious and causes A large number of bubbles; (3) The synthesis process is relatively complicated and the cost of raw materials is high

However, the content of commercial lignosulfonate on the market is generally no more than 60%, and also contains impurities such as reducing sugars and small molecular inorganic salts. The existence of these impurities affects the application performance of lignosulfonate, such as The presence of sugars makes the powdered lignosulfonate easy to absorb moisture when stored, and also has a retarding effect, resulting in a decrease in the early strength of the cementitious material

In addition, it has a three-dimensional network molecular structure, which is soluble in aqueous solutions with different pH values ​​and insoluble in organic solvents. Because of its wide molecular weight distribution, uneven composition and unstable properties, it greatly restricts its normal performance.