Research on the property improvement of PVC using red mud in industrial waste residue

Red mud is a red solid power waste that is discharged in the aluminium refinery industry during production. It is a strong alkali and can be categorized as polluting industrial residue. How to make comprehensive use of red mud has become a worldwide issue. In this paper, we put red mud into PVC (polyvinyl chloride polymer), taking advantage of the complicated chemical properties of red mud derived from the Bayer process. The results are compared with silica fume, coal ash and calcium carbonate under the same experimental conditions, which shows that improvement of PVC plastication can be achieved by adding red mud.


Introduction
Red mud is waste when refined alumina from bauxite. According to aluminum smelting methods which were divided into Bayer process red mud, Sintering red mud and joint method red mud. With the developing of the aluminum industry, the world produces almost 50 million tons of red mud annually. However, the main method for dealing with red mud is pilling up in the world, so how to comprehensively utilize red mud is a world problem [1][2][3][4]. Because the red mud dealing with alkaline solution, the alkali content is very high, and the pH content of red mud is 15%~30%, from 10.0 to 12.5. Because we don't make full use of the amount of red mud, plenty of land it occupies will lead to alkaline soil, polluted groundwater and harm to health. In order to resolve the problem of environment pollution, scientific scholars research the physical and chemical properties of red mud in the every country [5][6][7].
We found that there are two ways to deal with red mud: one is to recycle valued metals from the red mud [8][9][10]; the other is as a common mineral resources [11][12][13][14].
Earlier research about recycling iron from red mud is from the 1950s, and mang refining technology has been patented. Laszlo et al. [15] tested the red mud content many metallic oxide such as Fe 2 O 3 ,Al 2 O 3 and TiO 2 which respectively is 66%(mass fraction, the same below), 13.3% and 6.1%. Ercagt et al. [16] retrieved Fe,TiO 2 and Al 2 O 3 from smelting red mud in the electric-arc furnace. There has been not only research on retrieving metal, but also on recycling rare earth metals from red mud. Orhsenkuhnu [17]  produces cement high in iron oxide, special cement and ordinary portland cement. Tsakiridis et al. have researched producing portland cement technology by adding 3.5% red mud in raw material. With this method, the cement possesses higher early strength than ordinary portland cement in mechanics performance. Except for red mud as raw material produce cement, Sglavo et al. [18] studied red mud mixes with clay calcining ceramics. Additionally, red mud can remove impurities; Gupta V K et al. [19] used H 2 O 2 to treat Bayer process red mud to remove organic matter on the surface. Altundogan S et al. [20] studied red mud adsorption of As 5+ and As 3+ . This paper mainly researches the effect of Bayer process red mud on PVC organic material.

Equipment
The heat & cool mixer model is JZRL10/25. It is made of fuxin haoteer plastic machinery CO., LTD.
A ZJL-200A torque rheometer controlled by computer is made of Chuang chun Intelligent Apparatus CO., LTD.

Material
This test used many organic materials, such as PVC, stabilizer, Yellow foaming agent etc. Those materials types are listed in table 1. In order to find the results, sub-nanometer fly ash, fly ash, calcium carbonate and micro-spheres were used as fillers [21].
There are many fillers, and they will lead to different test results, so it is necessary to analyze their material microcosmic structure and chemistry aspects. The physical properties of red mud are listed in table 2.  Fly-ash: most pellets are globular (over 98%), withelectron microscope found Nanoparticles adhere to parts of the ball granule, developing framboidal texture, as shown in figure 1.   Light calcium carbonate: it is an important inorganic material that light calcium carbonate was made by chemistry method. It is also called precipitated calcium carbonate, and it has fine grain size, high whiteness, good crystal form, lower prices, etc. [22]. Glazed hollow bead: it is an acidic glassy lava mineral with its internal porous surface closed. It is made of SiO 2 Al 2 O 3 CaO. The SEM picture is shown in figure 3.

Testing method
The materials compounding as table 4. The temperature was set at 180℃, the affection of the rotor speed is 30 r/min, and the quantity of total material is 65 g.

Results and discussion
These figures show that under the same experiment, in figure 4 the curve of torque is a line parallel Xaxis in the process of test, it proved adding this material PVC did not plastify. But the curve of torque in figure 5 shown PVC mixed with red mud would plastify, so the red mud as adding possess character that promotes PVC plasticized in this test condition.

Conclusions
We made the follow conclusions:  As red mud contains rich chemical elements, it will help plasticized polyvinyl chloride plastified during maxing.  Mixed with appropriately mount of red mud will instead of parties processing adding in PVC.