The reaction of post-consumer poly(ethylene terephthalate) with aqueous solutions of sulfuric acid 7.5 M was investigated in terms of temperature, time and particle size. The reaction extent reached 80% in four days at 100°C and 90% in 5 hours at 135°C. TPA obtained was purified and considered in the same level of quality of the commercial one after tests of elemental analysis, particle size and color. It was concluded that the hydrolysis occurred preferentially at the chain ends and superficially, having as controller mechanism the acid diffusion into the polymer structure. The shrinking-core model can explain the reaction kinetics.

Catadores are people who collect and sell materials that can be recycled. This activity has been done informally in many countries for years. Recently, a recognition process has begun for the informal recycling sector, with public and private initiatives. In Brazil, catadores started out associating with each other in co-operatives in the 1980s. In 2010, the Solid Waste National Policy was approved, promoting the inclusion of theses co-operatives in the formal waste management system. However, only in 25 out of 5670 Brazilian municipalities have hired co-operatives as Private Service Providers. The integration of the informal sector has contributed with social, economic and environmental benefits; income generation, reduction of poverty and resource preservation are highlights. Although there was a legal progress, there are great challenges for various actors involved. This paper aims to diagnose the informal recycling sector, emphasizing the integration process that has happened in Brazil. For this, a substantial literature review and a case study were conducted, applying the tool ‘InteRa’ to the case of Sorocaba. The case showed that it is possible to improve the integration of catadores in the formal waste management system. The co-operatives achieve recycling rates of 2%, higher than the official national rate of 1%. However, we estimate that autonomous pickers increase total recycling in Sorocaba to 9%, still short of the 25% target via source segregation. Therefore, continuing the integration process will benefit both the pickers, and also the municipality through savings on landfill costs.

The neutral hydrolysis reaction of post-consumer poly(ethylene terephthalate) in solid state was studied through the reaction of the polymer with water at the molar ratio 1:91 with autogenous pressure. Two sizes of post-consumer PET flakes and temperatures of 135°C, 170°C and 205°C with pressures of 4.0 atm, 7.5 atm and 13.5 atm, respectively, were considered. With reaction time equal to 6h, the method reached 99% depolymerization at 205°C, 8.2% at 170°C and 1.7% at 135°C. The reaction extension was measured by separating the terephthalic acid formed in the process and calculating by gravimetry how much material could still be reacted. Through the viscosimetry of diluted solutions and the counting of carboxylic end groups in the remaining material from the gravimetric assay, it was possible to suggest that the reaction occurs randomly and in the whole volume of the polymeric particle and not solely on the surface. The terephthalic acid obtained and then purified was characterized by elemental analysis, magnetic nuclear resonance, size and particle size distribution and spectrophotometry in the visible spectrum, and it was similar to the petrochemical equivalent, with purity recorded in carbon base equal to 99.9%.