Type of the Paper Article

Figure 1. (a) Painting operations of vehicle parts (credit G. Salihoğlu); (b) automotive PS (credit B. Ruffino).

Italian automotive factories produce from 2.5 to 5.0 kg of PS per painted car [5]. If that figure is referred to the number of vehicles produced worldwide every year, in the order of 100 million, it determines an annual PS amount of 200,000–500,000 t, for which a proper final destination must be found.

PS is a very complex material, the exact composition of which depends on the type of paint used. The main components of PS are water and organic solvents, in addition to a variety of paint ingredients, including uncured polymer resins, curing agents, pigments, surfactants, and other minor formulation constituents [6]. The presence of uncured paint resins, which cure and form a film upon heating, makes PS very sticky and difficult to handle. Therefore, detackification agents are often added to the sludge for easier manage- ment of PS [7].
Some years ago (2016), Salihoglu and Salihoglu [4] published a comprehensive re- view concerning the PS coming from the automotive industry. In the first part of their work, they provided a detailed description of the environmental aspects of an automobile manufacturer. Subsequently, with the aid of mass balances, they demonstrated that the
primary source of hazardous waste at an automotive factory can be attributed to a single unit operation, namely automotive painting. They treated the aspects that concerned the generation and composition of PS with great detail, and, finally, they devoted the last section of their review to the management of PS. Some years after the work of Salihoglu and Salihoglu [4], this work intends to expand and complete the literature review pro- vided by the two authors, with a specific focus on the processes developed from the Nine- ties to the present day that aim not only to reduce the hazardousness of PS but, in line with the waste hierarchy and circular economy principles, to transform PS into valuable products and energy. To the best of our knowledge, there are no other review papers treating this subject. The management of PS has to be deemed a hot topic because of the growing demand for passenger cars that most of the European countries have recorded over the last 30 years [8], as shown in Figure 2.


800