Study On The Preparation Of Magnesium Oxysulfide Based Ecological Material

At present,people’s living environment is diversified and comfortable,and interior building decoration materials are emerging one after another.Many decoration materials will release formaldehyde.At the same time,the air tightness of the living space is improved,the circulation of fresh air is insufficient,and indoor air quality problems often occur.Relative humidity and formaldehyde content in indoor air are important factors affecting indoor air quality.Regulating indoor relative air humidity and purifying formaldehyde has become a problem that cannot be ignored.In this paper,a magnesium oxysulfide material matrix was prepared using light burned magnesium oxide,magnesium sulfate heptahydrate and water as raw materials,and the preparation ratio of the magnesium oxysulfide matrix was studied.It was modified with citric acid and diatomaceous earth to determine the best ratio analyzed its performance and formation mechanism.Used magnesium oxysulfide matrix,combined with modified diatomaceous earth and manganese dioxide,a magnesium oxysulfide-based ecological material that regulates indoor relative air humidity and purifies formaldehyde was prepared.Through X-ray diffractometer（XRD）,infrared spectroscopy（FTIR）,scanning electron microscope（SEM）,mechanical properties,setting time,water resistance,moisture absorption and desorption performance test,formaldehyde purification performance test and other methods to study the composition and performance.The main research results were as follows:（1）The flexural strength and compressive strength of the unmodified magnesium oxysulfide matrix prepared with light-burned magnesium oxide,magnesium sulfate heptahydrate and water as raw materials are only 10.09 MPa and 27.15 MPa.The initial setting time and the final setting time are 230 min and 270 min respectively,and the water softening coefficient is 0.53.The performance is not ideal,the main reason is that its main crystal phase is Mg O,Mg（OH）₂;The flexural and compressive strength of the magnesium oxysulfide matrix modified by citric acid reached 16.34MPa and 58.89 MPa,an increase of 61.9%and 116.9%.The initial setting and final setting time are extended to 500 min,565 min,and the water softening coefficient is0.86,which is an increase of 62.3%.The main reason is that citric acid can inhibit the formation of Mg（OH）₂and form a new crystalline 5·1·7 phase,the 5.1.7 phase forms a stable polymer network chain-like skeleton structure through self-assembly,which improves performance;The flexural and compressive strength of the magnesium oxysulfide matrix modified by citric acid+diatomaceous earth reached 18.81 MPa and 70.60 MPa,an increase of 86.4%and 160%.The initial setting and final setting time are 415 min and 465 min,and the water softening coefficient is 0.9,which is an increase of 69.8%.The main reason is that the formed polymer 5·1·7 phase is tightly combined with diatomaceous earth,and the material matrix is more dense.The optimal preparation ratio of magnesium oxysulfide matrix is that the molar ratio of Mg O,Mg SO₄·7H₂O,and H₂O is 8:1:20,and the addition amount of citric acid and diatomaceous earth is 1%and 20%.（2）The original diatomite soil can adjust the humidity in the range of 41%-62%.After calcining and pickling modification,the moisture absorption and desorption performance of diatomite is improved,and the humidity control range is 50%-55%.The diatomite-magnesium oxysulfide-based material keeps the relative humidity of the air within a comfortable range of 50%-55%.（3）The formaldehyde adsorption efficiency of diatomite original soil is 45.8%,and the formaldehyde adsorption efficiency of modified diatomite is still only 57.2%.Formaldehyde decomposition efficiency of manganese dioxide prepared by potassium permanganate and manganese acid is 94.5%,and the decomposition efficiency of formaldehyde purification effect durability test is 93.9%.The magnesium oxysulfide-based ecological material has a purification efficiency of 91.9%for formaldehyde,and the purification efficiency of the formaldehyde purification effect durability test is 90.6%,which meets the requirements for indoor air purification building decoration materials.