Recycling And Recovery Routes Of Plastic Solid Waste (Psw): A Review
Managing of plastic waste is big issues in the world, because the plastic waste is polluting the world as well as the ocean. This paper is about the recycling band recovering of the plastic solid waste (PSW). The main focus of this paper is on the plastic which is formed by the polyolefinic sources, which is widely used in the world and makes a big range of waste. The four methods of PSW treatment discussed in this paper are primary (re-extrusion), secondary (mechanics), tertiary (chemical) and quaternary (energy recovery) scheme and technologies.
Plastic is used in many application in our life daily, most of it finish up in the waste after using single time or after short of purchasing example food packaging. Re-using of plastic by recycling is more beneficial as it uses less energy and fewer resources. Re-using of plastic has many advantages like preservation of fossil fuel as it utilizes 4 to 8% of global oil production and decrease in energy and MSW etc. Many techniques have been made for sorting of PSW, some are manual and some are automated. But in case of plastic sorting automated techniques are not always applicable due to difference in shape, color and size, and due to existence of coatings and paints. There are many ways of sorting developed some of them are by using density, by triboelectric separation, by a speed accelerator technique. Sorting is the most important step in recycling of PSW. In recycling most difficult thing is to remove paint coatings on the plastic, even the quality of the plastic is decreased because of the concentration of these coatings. The high temperature aqueous-based paint removal method can be used for olefins because this type of plastic cannot be degraded. Degradation of the plastic decreases the resale value of the recycled final product. The re-extrusion also known as primary recycling, is recycling of scrap, industrial plastic edges and parts in the extrusion cycle to produce products of the same material.
The primary recycling is only used for semi-clean scrap. Main source of plastic waste is household, recycling of household waste is very challenging, and it involves significant operating cost.Mechanical recycling also called primary recycling recovers plastic via mechanical means. Recycling of PSW via mechanical recycling can be achieved only on single polymer plastic, the more complex the waste is, the more will be difficult to recycle the waste. There are many products found in our daily lives that come from mechanical recycling processes, such as grocery bags, pipes, gutters, window and door profiles, shutters and blinds, etc. recycling of PSW by mechanical process involves many treatment and preparation methods, which are size reduction, cutting/shredding, contaminant separation, floating, milling, washing and drying, agglutination, extrusion and quenching.
One of the best example PSW utilization is recycling of Polyethylene teraphthalate (PET). PET is mostly used in making fiber materials like carpet, apparel. Chemical recycling also called tertiary recycling is a advanced technology process which converts the plastic into smaller molecules mostly liquids and gases, these smaller molecules can be further used to make petrochemicals and plastics. The process used in the chemical recycling of plastic is de-polymerization, which provides high product yield and minimum waste. The plastic treated by chemical recycling is mostly used as a fuel.
