"White Pollution" and Recycling of Used Plastics

Together with iron and steel, wood, and cement, plastics together constitute the four basic materials of modern industry and play an important role in the development of the national economy. Plastics have the advantages of excellent material comprehensive performance, convenient processing, significant energy saving in production and use, etc., making them widely used in industry and agriculture and people's daily life. With the vigorous development of the plastics industry and its large-scale use, environmental pollution caused by waste plastic products and plastic waste has become increasingly serious. The disposal and disposal of plastic products has caused a series of environmental problems, and â€œwhite pollutionâ€ has become a household name. Plastic materials are synonymous with environmental pollution and have become a global environmental hazard. Correctly understanding the impact of waste plastics on the environment and actively studying their handling and disposal processes are of great significance to the protection of the environment and the use of resources.

1 Environmental Impact of Waste Plastics

1.1 "White Pollution" Caused by Waste Plastic Packages

Plastics are widely used as packaging materials for various products because of their low cost and convenient molding. With the development of the modern plastics industry and the improvement of consumption levels, most of them are disposable products, which are disposable and cause environmental pollution. For example, it is used as a white foamed polystyrene plastic for household appliances, industrial instrumentation and other packaging and fast food boxes, beverage cups, etc. It is characterized by large volume, light weight, no decay, no decomposition, abandoned by people after use. Caused by the railway along the river, river routes, cities and scenic spots are full of white foam, seriously affecting the environment and the appearance of health, was known as "white pollution."

According to reports in the literature, in 1995, the total output of plastic products in China was nearly 7 million tons, of which about 1.7 million tons were used for packaging. About 500,000 tons of these packaging materials were used as solid waste to enter the municipal solid waste treatment system, and the other part was Users readily throw litter to form plastic waste. These plastic wastes were abandoned on the roadsides, green areas, or tree-lined trees of bustling cities and tourist attractions, damaging the urban landscape and affecting the appearance of the city. In windy cities, plastic bags littered with the wind posed a disturbance to the city's power supply system. In 1996, the electrical department in Tianjin caused more than ten accidents due to short-circuit accidents caused by plastic bag winding overhead power supply lines. Plastic packaging for food and beverage packaging is a breeding ground for mosquitoes, flies and bacteria to survive and reproduce. It is easy to cause the spread of germs, affect environmental health and the public health of the urban public.

1.2 Environmental Impact of Waste Plastics Landfill Treatment

The disposal of landfills as garbage into municipal landfills is currently the main method of disposing of used plastics. With the rapid development of the plastics industry, the output of waste plastics is directly proportional to the environmental problems caused by it. First, landfills occupy limited farmland and waste land resources. The second is that plastic waste will not be rotted after being landfilled and will harm the future. Corrosion resistance and bacteria resistance are a big advantage of plastic products, but they become a headache for scientists after they become garbage. Under conditions without air or light, microbes are difficult to decompose organic substances. Plastic waste needs 200 years of time in landfills. Can be decomposed. The third is that after landfill plastic waste is washed through the rain for a long time, so that a large amount of harmful substances are brought into the living environment of human beings, causing harm to future generations. From the above, it is a long-term effect that the environmental pollution of plastic wastes is treated by the landfill method, and such methods should be avoided in practical disposal.

The use of agricultural mulch has brought great development to agricultural production. However, the fragmentation after mulching has also caused great harm to the soil. Film debris forms a barrier on the soil, degrading the arable land, and hindering the development of the root system of the plant. Absorb moisture and nutrients to poison the soil.

1.3 Impact of Waste Plastics Incineration Treatment on the Environment

In order to solve landfill land occupation, high cost, and long-term damage to the environment, many countries are actively developing incineration of waste plastic equipment, and use the heat generated by the incineration to generate electricity and achieve resource reuse. However, this seemingly simple and easy method hides great harm.

In the process of thermal decomposition of plastics, the polymer is cracked, releasing a large amount of harmful gases, such as polystyrene plastics can keep the composition of the substance below 80Â°C. When the temperature exceeds 280Â°C, its molecular weight begins to decrease, resulting in volatile. Gases and gases contain 44% styrene monomer, 22% dimer, trisomics, and small amounts of toluene, ethylbenzene, etc. These are all harmful substances that are harmful to the environment. Incineration of polyvinyl chloride plastics not only produces chlorine, hydrogen chloride, and dioxin gas that are extremely destructive to the environment, but also produces harmful gases such as C0, N0x, formaldehyde, vinyl chloride, and styrene, which have a great impact on the ecological environment.

In the plastic incineration process, inorganic materials such as plastics filling and dyeing are also volatilized in the atmosphere, such as Pb, As and other harmful substances, causing air pollution.

From the above, it can be seen that with the continuous development of the plastics industry, the impact of plastic waste on the environment is increasing, which has already caused certain damage to people's production and life. Therefore, how to prevent the damage of plastic waste has become a hot issue for plastic workers and environmental protection workers in various countries. In addition to the landfill and incineration methods, the current methods of processing plastic waste include chemical methods and physical methods that are based on the principle of reduction, harmlessness, and resource recycling, so that plastic waste can be resource-resourced and turned into waste. For the benefit of mankind.

2 Waste and Recycling Treatment Methods and Techniques

The recycling of waste plastics is an important means of protecting the environment and is an important way to make full use of human resources. According to reports, the average annual growth rate of recycled plastics in the United States reached 16%, reaching 215 million tons in 1988. China's plastics industry started late, and the recycling of waste plastics has just started. In some major cities, some self-employed people deal with waste plastics with low-cost equipment and cheap labor. These small stalls are weak due to lack of funds and technical strength. Secondary pollution is caused in the treatment, causing more serious damage to the environment. For instance, in the case of collective poisoning of more than 80 elementary school pupils at the Qinjiamiao Primary School in Qixian County, reported by Chengdu Commercial News in June 1999, investigations revealed that a certain operator had caused leakage of poisonous gas when using cheap equipment to dispose of waste plastics. It was also reported that the use of hospital disposable plastic needles in the manufacture of privately-packaged food bags at a single-stream processing station in Shuangliu was conceivable.

2.1 Waste Plastics Recycling Treatment Methods

The recycling of plastics is different from the recycling of metals, paper and glass. Because of the differences in the physical and chemical properties of various plastics and the incompatibility of various plastics, their mixtures are not suitable for processing. Therefore, each plastic must be separately collected. , and then dealt with in different ways. In the process of collection and classification, it is necessary to prevent the mixing of dirt and foreign impurities, otherwise it will affect the reuse of recycled materials.

Different kinds of plastics, there are major differences in service life, such as low-density polyethylene film products, the service life of 1 to 2 years; PVC pipe has a long service life, up to 10 years. Therefore, in the processing of waste plastics should be based on the plastic source, type, contamination and mixing conditions, select the appropriate recycling methods, in order to convert the waste plastic into a suitable material for further processing. Table 1 shows how to regenerate different kinds of plastics.

Table 1 Treatment Methods for Different Kinds of Plastics

Raw material

Processing Method Product Category