Study On The Preparation Of Environmentally Friendly Snow Melting Agent By Extracting Aluminum-iron Silicon From Red Mud And Its Properties

In many cold areas,the winter snow brings great inconvenience to people's travel and traffic.Vehicle braking performance on the ice and snow surface is poor,which can easily lead to traffic accidents.Chlorine deicing salts are widely used in road snow removal because of its high capacity of snow melting and low price.However,the chloride deicing salts have more serious damage to roads and bridges,and have some damage to the plants and water on both sides of the road.In this study,a new type of deicing salt was prepared to overcome the disadvantages of using traditional chlorine deicing salts and its performance is studied.Firstly,in this paper,iron and aluminum were leached from red mud by dilute hydrochloric acid.The results showed that under the condition of dilute hydrochloric acid(3 mol·L^-1)at 90°C at a solid to liquid ratio 1:16,and the leach time was 90 min.The leaching rate of aluminum can reach 66.7%,and the leaching rate of iron can reach95.4%.Then,the aluminum chloride and ferric chloride extracted from red mud were mixed with calcium chloride,adding calcium hydroxide as pH regulator,and the optimum ratio of CaCl₂/AlCl₃/FeCl₃/Ca?OH?₂ was 10:5:2:3.After mixing and grinding,the Ca-Al-Fe deicing salt was prepared.Freezing points of this deicing salt?Ca-Al-Fe deicing salt?were determined at concentrations of 5,10,20,30 and 40 wt%,and the numerical values were in the range of-6.6^-22.5°C.A dense layer of precipitation membrane can be generated on the concrete surface to prevent further immersion of chloride ion during deicing process,due to the addition of aluminum chloride and ferric chloride,the Ca-Al-Fe deicing salt can adsorbed chloride ion while melting snow.By the XRD test,the main components of the precipitation membrane were Ca₂Al?OH?₆Cl·2H₂O and FeOOH.In order to improve Ca-Al-Fe deicing salt melting snow and ice ability to apply in alpine region,the composition of Ca-Al-Fe deicing salt was adjusted.When the best ratio of CaCl₂/AlCl₃/FeCl₃/Ca?OH?₂ was 14:3:1:2,freezing points of this deicing salt were determined at concentrations of 5,10,20,30 and 40 wt%,and the numerical values were in the range of-7.4^-36.5°C.The silica was extracted from the red mud to prepare Na₂SiO₃·9H₂O as a corrosion inhibitor to Ca-Al-Fe deicing salt.The experiment showed that the optimum addition amount of Na₂SiO₃·9H₂O was 2.25 g·L^-1,and the corrosion rate of carbon steel was 0.078 mm·a^-1.In order to improve the frost resistance of the precipitation membrane,sodium methyl silicate was added as hydrophobic agent.The optimum addition amount of sodium methyl silicate was 2 g·L^-1.A hydrophobic layer was formed on the surface of the precipitation membrane.After the formation of hydrophobic layer,the water absorption rate of concrete was reduced by79.3%,and compared with calcium chloride the frost resistance was reduced by 96.1%.The Ca-Al-Fe deicing salt developed in this paper preserves the advantages of chlorine deicing salts,and meanwhile,adsorbs the free chloride ions in the deicing salt solution to reduce the corrosion of deicing salt to carbon steel and concrete,and reduces the influence on the environment.And the material recovered from the red mud as a raw material to reduce the production cost of deicing salt,while achieving the effective use of red mud and the harm of red mud to environment is reduced.