How To Clean PET Bottles?

I. The Importance of Cleaning PET Plastic Bottles

PET plastic bottles are ubiquitous in our daily lives and are widely used in various fields such as beverages, food, and daily chemical products. With the continuous improvement of environmental awareness and the increasing importance of resource recycling, the cleaning of PET plastic bottles has become crucial.

Firstly, from an environmental perspective, cleaning PET plastic bottles can help reduce the pollution of plastic waste to the environment. A large number of PET plastic bottles that have not been cleaned and disposed of indiscriminately not only damage the natural landscape, but may also cause serious harm to soil, water sources, and other areas. By cleaning PET plastic bottles, they can be recycled and reused, reducing the demand for new plastic raw materials and thus reducing energy consumption and greenhouse gas emissions in the plastic production process. This has positive significance for protecting the ecological environment and promoting sustainable development.

Secondly, cleaning PET plastic bottles can achieve the reuse of resources. PET plastic is a recyclable material that can be processed and cleaned to produce various recycled products, such as recycled fibers and plastic sheets. These recycled products can to some extent replace native plastics and reduce dependence on natural resources. Meanwhile, recycling PET plastic bottles can also reduce production costs and improve the economic efficiency of enterprises.

In addition, cleaning PET plastic bottles also plays an important role in ensuring consumer health. Uncleaned PET plastic bottles may contain various harmful substances such as bacteria, viruses, chemicals, etc. If these bottles are reused for packaging food or beverages, it may pose a threat to consumers’ health. By cleaning, these harmful substances can be effectively removed to ensure the safety of PET plastic bottles.

In short, the cleaning of PET plastic bottle has important environmental protection, resource reuse, and health protection significance. In today’s world where environmental protection and sustainable development are advocated globally, we should attach importance to the cleaning of PET plastic bottles and promote the development of the PET plastic bottle recycling industry.

II. Common Cleaning Methods

1. Household Cleaning Methods

There are some simple and practical methods for cleaning PET plastic bottles at home. Firstly, you can prepare a small basin of hot water, pour a small amount of detergent into it, and then stir the water and detergent evenly. Next, soak the PET plastic bottles that need to be cleaned, such as oil pots, in hot washing solution for about a minute. Afterwards, wrap the soaked oil drum with kitchen paper, then wrap it with plastic wrap and let it sit for about half an hour. After the time is up, remove the outer layer of plastic wrap and tissues, put the oil pot back into the washing solution, and gently wipe the green rough side of the scouring pad to remove the oil stains.

You can also pour a small amount of rice into the oil drum, add a small amount of water, and screw the lid of the oil drum tightly. After shaking it up and down vigorously, you will find a lot of black sediment at the bottom of the drum. Afterwards, put the unused eggshells into the oil drum, add water as the previous step, and shake a few more times. If there is still black sediment at the bottom of the bucket that has not been removed, you can add eggshells, vinegar, and an appropriate amount of water again, and then shake vigorously a few more times to thoroughly clean it.

For regular PET beverage bottles, a few drops of detergent and water can also be added to the bottle, and any hand sanitizer can be used to wash plastic bottles. After adding some dishwashing detergent, fill the bottle halfway with warm water and cover it with a lid. Shake for a while, then rinse with clean water. Alternatively, shake the dishwashing soap and water in a bottle and then pour. To achieve the fastest cleaning effect, simply shake the soapy water on the bottle cap for one minute. Then pour out the soapy water and rinse thoroughly. For bottles with a pull-up or flip top straw, you can use a small bottle brush to enter the small crack in the opening and manually scrub the top with a soap sponge or brush.

For newly purchased PET plastic bottles, lemon peel, orange peel, and vinegar can be used for cleaning. Put a few slices of lemon peel and orange peel in a cup, or drop a few drops of vinegar, and soak overnight to remove the odor from the plastic bottle. You can also use expired milk and soak a cloth inside to wipe the cup, which can quickly remove odors and dirt. You can also soak it in rice washing water overnight. This method is not only suitable for plastic bottles, but also for glass cups, stainless steel cups, and ceramic cups.

2. Industrial Cleaning Method

The process of cleaning PET plastic bottles in industry is relatively complex, mainly including sorting, crushing, pre-washing, main washing, rinsing and other steps.

Sorting is the process of separating impurities such as bottles, colored bottles, trademark paper, and bottle caps that are not PET from raw materials. Some things (such as trademark paper, bottle caps, etc.) can be removed in the later process, while some things (such as PVC/PS/rubber, etc.) cannot be separated in the later process. They must be cleaned during the sorting process, otherwise good bottle fragments cannot be washed out.

Crushing is the process of crushing sorted single color pure PET bottles into pieces. There are two types: dry powder and water powder. Currently, water powder is generally used. The equipment is cheap, efficient, and free of dust pollution. Some manufacturers have already changed their crushers to ones with washing drums, which can serve as a pre-wash and have a good effect.

The pre-washing process is mainly to remove the easily removable stains adhered to the surface of the bottle. After crushing, the wool flakes are covered with a lot of dirt such as sand, debris, and oil stains. The pre-washing process is to wash away the easily removable impurities such as sand and debris with water. The main function of pre-washing is to reduce the burden of the main washing process, improve cleaning quality, reduce the amount of cleaning agents, lower costs, and control pollution.

The main washing is a crucial step in the entire process, which mainly involves removing stains such as oil and glue. In this process, cleaning agents are used, and some techniques also require heating. Whether this step is done well or not directly determines the quality of the bottle slices.

The rinsing process has two functions: one is to remove the remaining floating material, and the other is to remove the cleaning agent adhered to the bottle.

The PET plastic bottles recycled by the plastic cleaning machine first go through a “label removal machine” to remove the labels on the bottle body, and then go through a “flat sorting conveyor” to select the mixed color bottles (such as green bottles, blue bottles, residual impurities, etc.) in the material, and then enter the “crusher” for powder crushing. After that, they enter the “rinsing water tank” for separation (to achieve the separation of PET bottle pieces from PP label paper and bottle caps).

After separation, they enter the “high-temperature pot” for heating and cleaning, and then enter the “rinsing water tank” for rinsing (to remove the cleaning agent in high-temperature heating). After dehydration in the “dehydrator”, they are directly packaged. We can achieve high-precision and clean flakes through a complete set of fine washing processes, including whole bottle pre-washing, label removal and sorting, initial crushing, initial washing and separation, high-temperature cleaning, neutralization cleaning, rinsing and drying, and bottle flake selection, in order to achieve high production volume and high bottle flake grade.

This process is a routine process, and depending on the production location and output requirements, the factory can also design different production plans according to customer needs.

III. Cleaning Difficulties and Solutions

1. Cleaning Difficulties

The market for cleaning agents is chaotic: the plastic sheet cleaning agent market is relatively chaotic and there is no unified cleaning standard. This makes it very difficult to determine which cleaning agent can effectively clean PET plastic bottles, while also increasing cleaning costs and risks.

Complex and difficult to remove dirt: The surface of plastic bottles is mixed with various types of dirt, and the types of oil stains are complex, and the sticky adhesive paper marks are difficult to remove. These dirt not only affect the appearance of plastic bottles, but may also have adverse effects on the subsequent recycling process.

High temperature cleaning can easily cause yellowing of plastic sheets: High temperature cleaning can easily cause yellowing or blackening of plastic sheets, resulting in a decrease in glossiness. This is because plastic bottles may undergo chemical reactions at high temperatures, resulting in color changes and reduced glossiness. This situation not only affects the appearance quality of plastic bottles, but may also reduce their recycling value.

2. Cleaning Solutions

Selecting specific surfactants to prepare cleaning agents: By testing the degreasing and debonding abilities of various surfactants on plastic sheets, as well as improving whiteness, a complete formula system was finally formulated using surfactants and additives such as Suractent228S and Suractent8096S. High temperature drum cleaning above 80 ℃ for 20 minutes can completely clean various oil stains, sand particles, offset printing, dust and other dirt on the surface of plastic sheets. Especially after adding Suractent8096S to the formula, the whiteness of the cleaned plastic sheets can be significantly improved.

Cleaning agent formula: An efficient regenerated PET bottle cleaning agent, with a composition and weight percentage of 4-10 percent of cleaning powder, 1.5-3 percent of strong alkali, 0.3-1 percent of corrosion inhibitor, and 80-95 percent of water. Cleaning powder includes inorganic salts and hydrophilic surfactants. Inorganic salts include one or more of carboxylate salts, sulfate salts, quaternary ammonium salts, fatty polyoxyethylene derivatives, and lactones. Hydrophilic surfactants are aliphatic polyoxyethylene ethers. Strong alkali refers to one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, and calcium hydroxide. Corrosion inhibitors are one or more of sodium benzoate, sodium borate, aluminate, inorganic acid, and amine.

Cleaning method: Prepare cleaning agents according to the amount of PET bottle slices, add cleaning powder, strong alkali, and corrosion inhibitor to a high-speed mixer, and mix at room temperature for 5-10 minutes to obtain a mixture. Add water to the boiling pot and heat it until the water temperature reaches 85 ° C or above. Mix the mixture evenly into the pot while continuously stirring the water. Wait until the mixture is completely dissolved, and the mixture becomes a semi transparent clear liquid without suspended solids or sediment. Then, add crushed PET bottle slices for cleaning, with a cleaning time of 5-10 minutes. Place the cleaned PET bottle slices in an oven and heat treat them at 220 ° C for 20 minutes before testing.

In addition, the following measures can also be taken to solve the cleaning difficulties.

Adding pre-washing equipment: can reduce the amount of cleaning agents used and improve cleaning quality.

It is recommended to use medium temperature cleaning: such as cleaning at 70 ℃, which can clean more thoroughly and avoid yellowing of plastic sheets caused by high temperature cleaning.

Using PET bottle cleaning agent: PET bottle cleaning agent is a universal cleaning agent that can be used at room temperature to quickly remove various stains such as oil, sugar, protein, etc. adhered to the bottle, quickly penetrate the adhesive of the label paper, and separate the paper from the bottle. But this cleaning agent also has some drawbacks, such as not being able to remove the text and patterns directly printed on the bottle, and not being able to completely remove the adhesive on the label paper at room temperature. It requires moderate temperature (60-70 ℃) to be completely removed.

In summary, the difficulties in cleaning PET plastic bottles can be addressed by selecting specific surfactants to prepare cleaning agents, using efficient recycled PET bottle cleaning agents and methods, increasing pre-washing equipment, and using medium temperature cleaning to improve cleaning effectiveness and quality, and promote the recycling of PET plastic bottles.

IV. The Treatment of Wastewater of PET Plastic Bottles Cleaning

1. Introduction of Pollutants

The PET plastic cleaning wastewater contains various pollutants, mainly including the following categories:

Organic pollution: Waste plastics mainly come into contact with or are packaged in food, feed, beverages, etc., leaving various organic residues.

PH pollution: The alkaline substances mainly added during the crushing and cleaning process of waste plastics cause changes in the pH value of the wastewater.

Suspended solids pollution: Waste plastic agricultural film and greenhouse film mainly come into contact with or package chemical fiber soil dust, waste plastic particles, etc., forming suspended solids pollution.

Oil pollution: Waste plastic PET bottles mainly come into contact with or package oily substances, which increases oil pollution.

2. Handling Methods

The treatment of PET plastic cleaning wastewater is mainly divided into three categories: physical treatment, chemical treatment, and biological treatment.

Physical treatment method: Separate and recover insoluble suspended pollutants (including oil film and oil droplets) from wastewater through physical action. Usually, methods such as precipitation, filtration, centrifugal separation, air flotation, evaporative crystallization, and reverse osmosis are used to separate suspended solids, colloids, and oil pollutants from wastewater, thereby achieving initial purification of the wastewater. For example, precipitation method can be used to precipitate heavier particles to the bottom of the water, and impurities of larger particles can be removed by filtration. Centrifugal separation can be separated based on the density difference of substances. Air flotation method uses small bubbles to make suspended matter float up. Evaporative crystallization can be used to separate soluble substances. Reverse osmosis can effectively remove small particles and soluble substances from water.

Chemical treatment method: Separation and removal of dissolved and colloidal pollutants in wastewater through chemical reactions and mass transfer, or conversion into harmless substances. The commonly used methods include neutralization, coagulation, oxidation-reduction, extraction, stripping, stripping, adsorption, ion exchange, and electroosmosis. For example, neutralization method can adjust the pH value of wastewater, coagulation method can condense small particles into large particles for precipitation and removal, oxidation-reduction method can change the chemical properties of pollutants to convert them into harmless substances, and adsorption method uses adsorbents to adsorb pollutants in water.

Biological treatment method: Through the metabolic process of microorganisms, pollutants such as wastewater solutions, colloids, and fine suspended organic and toxic substances are transformed into stable and harmless substances. Biological treatment methods are divided into two types: aerobic treatment and anaerobic treatment. The commonly used aerobic treatment methods currently include activated sludge process, biofilter, and oxidation pond. In the activated sludge process, microorganisms decompose organic matter under aerobic conditions to form activated sludge, which is then separated into clean water through precipitation.

Biological filters use microbial membranes on filter media to remove pollutants. Oxidation ponds utilize the combined action of microorganisms and plants in natural ecosystems to purify wastewater. Anaerobic treatment method, also known as bioreduction treatment method, is mainly used to treat high concentration organic wastewater and sludge, and the treatment equipment mainly includes digestion tanks. Under anaerobic conditions, microorganisms decompose organic matter into gases such as methane to purify wastewater.

Different processing methods are applicable to different situations. The physical treatment method is suitable for removing larger particles and suspended solids, and has a good initial purification effect on wastewater; Chemical treatment methods can selectively remove specific pollutants, but the cost is relatively high; Biological treatment is suitable for treating biodegradable organic matter, with relatively low operating costs but longer processing times.

3. Processing Flow

The process of treating PET plastic cleaning wastewater is as follows:

Plastic cleaning wastewater first passes through a basic sedimentation tank or grid to remove larger floating debris and particles. Then enter the biological pool and establish an environment suitable for microbial growth through adjustable aerobic or anaerobic conditions.

In the biological tank, the carrier packing forms a fluidized bed in the aeration zone vortex, and is well dispersed and suspended under the stabilizing effect of anaerobic/aerobic fluidized bed in the non aeration zone. The shear force present in the vortex ensures the high activity of the biofilm. Thus, the stable maintenance of the system carrier can meet the process requirements.

After biological treatment, the wastewater enters the secondary sedimentation tank. In the secondary sedimentation tank, activated sludge is separated from clear water sedimentation. Part of the sludge is returned to the biological tank as reflux sludge and continues to participate in the biological treatment process; Another part of the excess sludge enters the sludge tank for subsequent treatment.

Finally, clean water flows out and is discharged to achieve the purpose of wastewater purification. If the discharged sewage can be mixed with housdhold sewage, its biodegradability can be improved, and the discharge effect will be better after biological treatment. At the same time, coagulation treatment can also be used to remove most of the suspended solids in the sewage, and then the sewage can be reused in the production process to reduce the amount of sewage discharge.

V. Trends of Future Development

With the continuous advancement of technology and the increasing awareness of environmental protection, PET plastic bottle cleaning technology is also constantly developing and innovating. In the future, PET plastic bottle cleaning technology will develop towards high production capacity, high efficiency, high automation, and low cost.

1. Large Production Capacity

At present, the market’s demand for recycling PET plastic bottles is constantly increasing, and in order to meet this demand, cleaning technology needs to have greater production capacity. For example, some large PET bottle recycling and cleaning lines have been able to achieve a processing capacity of several tons per hour. In the future, with the continuous advancement of technology, production capacity is expected to further increase. On the one hand, by optimizing the equipment structure and process flow, the processing capacity of the equipment can be improved. For example, using more efficient crushing equipment and cleaning devices can process more plastic bottles in a shorter amount of time. On the other hand, the number of production lines can be increased to achieve large-scale production. At the same time, by increasing the automation level of equipment, reducing manual intervention, and improving production efficiency.

2. High Automation

With the development of technology, the application of automation technology in the field of PET plastic bottle cleaning will become increasingly widespread. At present, some advanced cleaning equipment has achieved partial automation operations, such as automatic feeding, automatic sorting, automatic cleaning, etc. In the future, cleaning equipment will become more intelligent and capable of achieving fully automated production. For example, using robots for operation can not only improve production efficiency, but also reduce errors and safety hazards caused by manual operation. At the same time, automation technology can also achieve remote monitoring and management of equipment, improving the stability and reliability of equipment operation.

3. Low Cost

Reducing costs is an inevitable trend in the development of PET plastic bottle cleaning technology. To achieve low-cost cleaning, we can start from the following aspects. Firstly, optimize equipment design and manufacturing processes to reduce equipment manufacturing costs. For example, by adopting advanced manufacturing technology and materials, the performance and reliability of equipment can be improved while reducing the manufacturing cost of the equipment. Secondly, improve the energy utilization efficiency of equipment and reduce energy consumption costs. For example, by using energy-saving equipment and technology, such as energy-saving bottle cleaning machines, energy-saving devices are installed to allow the cleaning brush on the outside of the third shaft to clean the bottles placed on the top of the first and second rotating sleeves.

During the cleaning process, multiple sets of shafts can be driven to rotate by a single driving motor, achieving a relatively energy-saving goal and facilitating the cleaning of PET bottles. At the same time, the device is equipped with a pushing device, which avoids the situation of manually pushing the bottle and facilitates the cleaning of PET bottles. In addition, by increasing the automation level of the equipment, labor costs can be reduced. For example, using robots for operation can not only improve production efficiency, but also reduce errors and safety hazards caused by manual operation, and lower labor costs.

In short, the future PET plastic bottle cleaning technology will develop towards high production capacity, high efficiency, high automation, and low cost. This will provide stronger support for the recycling of PET plastic bottles and promote the development of environmental protection.