Ecological and hygienic evaluation of sorbents recycled plastic waste

Abstract

Introduction. Prevention and minimization of the consequences of oil spills is due on the one hand to a high degree of environmental danger, and on the other - to the ever-increasing volume of oil consumption. It is known that oil, entering the ecosystem, brings with it a diverse set of chemical compounds that disrupt the existing geochemical balance and do not reversely change certain parts of natural biocenoses. Self-cleaning and self-restoration of oil-contaminated ecosystems is a complex and lengthy process. Therefore, measures and means to eliminate the consequences of accidents and prevent the ingress and spread of oil in the environment are relevant.

The most promising and environmentally safe is the method of removing oil from the water surface using petroleum sorbents. Synthetic sorbents are most effective for collecting oil, because their ability to sorb oil can reach a weight ratio of captured oil and sorbent of 40: 1 compared to a ratio of 10: 1 for organic products and an even lower ratio of 2: 1 for inorganic.

Of particular interest are fibrous composite petroleum sorbents from polymer waste. Availability and cheap raw materials reduce the cost of sorbents and expand the scope of polymer waste to solve environmental problems. However, the share of waste-based sorbents is less than 12% and almost all of them are of natural organic origin and are characterized by a low degree of oil recovery and high water absorption. Most natural sorbents cannot be regenerated, which turns them into a huge amount of highly toxic waste that needs to be specially stored, disposed of or recycled.

The direction of application of polymer waste as sorbents has not been developed because, as raw materials have been studied, "pure" polymer waste is scarce. The system of waste collection, separation and supply has not been established, which has made the area unattractive for investment. Absolutely different, economically promising and environmentally safe, is the direction of attracting large tons of household polymer waste as a raw material for the manufacture of petroleum sorbents. The raw material base is high-tonnage and is constantly growing in the range from 0.3% to 5%. Systems for collection, storage and supply of polymer household waste are developed.

Today, the most environmentally friendly and least economically expensive is the mechanical processing of polymers. Therefore, research to obtain petroleum sorbents from polymeric household waste are relevant, promising, both hygienically and economically.

The purpose and objectives of the study. The purpose of the research was to investigate the influence of mechanical methods of processing polymeric household waste on the change of their sorption properties and to develop the technology of obtaining petroleum sorbents on the basis of mechanically recycled polymeric household waste.

To achieve this goal it was necessary to solve the problem - to determine the oil-absorbing properties of sorbents on the basis of mechanically processed household waste depending on changes in their physical properties.

Methods and methodical: hygienic, physicochemical, statistical analysis. The oil absorption of sorbents was determined according to the method described in ASTM international F 726-12. Standard Test Method for Sorbent Performance of Adsorbents.

Results. It is experimentally established that at t = 21 ºC the value of oil absorption of mechanically processed household waste varies depending on the size of the fibers and the degree of its mechanical activation:

 - for sorbents made of PET in the range from 17.2 g / g to 32.4 g / g;

- for sorbents from PVC in the range from 12.7 g / g to 16.2 g / g;

- for sorbents from mixtures of PE + PP from 15,2 g / g to 38,7 g / g.

The bulk of petroleum products was sorbed in the first 3-5 minutes. Longer contact of sorbents from mechanically recycled household waste did not significantly increase oil absorption (less than 5%).

The best sorption characteristics have mechanically processed and activated fillers from mechanically processed household waste the size of the filler particles:

- for PET 1.5 × 40 (60) mm and 2 × 40 (60) mm, which corresponded to the maximum values of the specific surface in combination with spiral-like deformation of polymer plates;

- for PVC - 2,5 (3,0) × (30-120) mm;

- for mixtures PE + PP with a width of (3.5 - 5.0) mm and a length of (60-100) mm.

Conclusions and prospects. Experimental studies have shown that the value of the oil absorption of polymer waste at t = 21 ºC varies from 12.7 g / g to 38.7 g / g depending on the type of polymer and the size of mechanically recycled household waste. The best sorbed oil was mechanically processed household waste of PE + PP mixtures with a filler size from 3.5 mm to 5.0 mm wide and from 60 mm to 100 mm long, which corresponded to the maximum values of the specific surface of the polymer particles.

It has been experimentally proven that sorbents from mechanically processed household waste are effective for collecting oil from the water surface. The resulting sorbents from mechanically recycled household waste are much more efficient than any natural sorbents used to collect oil during accidents.

However, synthetic sorbents should be used in the smallest amount sufficient to ensure their maximum efficiency in order to reduce waste that requires special disposal.