Preparation Of Blue Ultramarine Pigment From Coal Gangue, Waste Molecular Sieve And Biomass And Its Acid Resistanc

Natural ultramarine blue pigment was the best pigment used by painters in the European Renaissance,usually used in the Virgin Mary,symbolizing the holiness.In1828,French scientists first discovered the artificial preparation method of blue ultramarine pigment.The use of ultramarine blue pigments has rapidly spread due to the relatively low cost of the new synthetic method of manufacture.At present,the main way of artificially synthesizing ultramarine is the soda ash sulfur method,that is,it is prepared by calcining kaolin as the main raw material.Ultramarine pigment is still used as a valuable inorganic pigment in today’s society,but to a certain extent,it is restricted by factors such as resource shortage caused by over-exploitation of raw materials and its weak acid resistance,which affects its production.Therefore,it is of great significance to develop raw materials and processes for preparing ultramarine pigments.Silicon aluminum is the main component of ultramarine,and carbon is the reducing agent in the preparation process.The coal gangue produced in the coal mining process and the industrially discarded discarded molecular sieve catalysts contain a large amount of elements such as silicon and aluminum,and the discarded biomass such as corn stalks in the agricultural production process are high-quality carbon resources.Serious environmental pollution and waste of resources.In order to realize the resource utilization of solid waste and reduce the production cost of ultramarine blue,this paper proposes a method to prepare blue ultramarine blue pigment with reasonable combination of coal gangue,waste molecular sieve as raw material,and corn stalk as reducing agent.When the mass ratio of coal gangue:waste molecular sieve:Na₂CO₃:S:corn straw is 1.50:0.50:2.50:3.50:1.00,the primary and secondary calcination temperatures are 400°C and 900°C,respectively,and blue ultramarine blue is successfully prepared.Pigment,and the structure and composition of the product were characterized by X-ray diffraction analysis（XRD）,infrared spectroscopy（FTIR）and scanning electron microscopy（SEM）.In order to explore the mechanism of preparing ultramarine blue pigments with different degrees of blue from coal gangue,methanol industrial waste molecular sieves and agricultural waste corn stalks as raw materials,the internal chromophore of the pigment was investigated by UV-Vis-DRS technology.The effects of Na₂CO₃/S mass ratio,primary calcination conditions,secondary calcination conditions and the dosage of raw materials on the content of chromophores in the prepared products were investigated during the preparation of ultramarine blue pigments.The results show that the brighter the color of the ultramarine pigment,the greater the ratio between the chromophores S^3-and S^2-.This research will provide a rational support for the preparation of ultramarine blue pigments from other minerals or wastes.In order to increase the acid resistance of ultramarine blue pigments,the paper discusses the conditions of using ethyl orthosilicate as a precursor and ammonia water as a catalyst to coat a thin layer of Si O₂ on the surface of blue ultramarine blue pigments.4.50 ml of water was added to the blue pigment,1.20 ml of TEOS and 2.50ml of ammonia water were added dropwise at the same time,and the reaction was carried out for 6.00 h.A dense and uniform Si O₂ coating layer was formed on the surface of the ultramarine blue particles p H=2.50-3.00 acid solution exists for more than 156 h without fading.