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Organic waste-to-energy (OWtE) technologies are playing a steadily increasing role in the Green Transition, thus becoming a powerful driver in the establishment of an ever more efficient and sustainable circular economy. The advantages of OWtE processes are well known: not only do they reduce the waste volumes sent to landfills or incineration plants, but also and foremost, through the energy they yield (biogenic carbon dioxide, amongst others), they reduce dependance on fossil fuels. This article gives a complete panorama of these technologies, starting from the classical methods and ending with a review of the latest modern novelties. Advantages and disadvantages of each method are highlighted, with particular focus on the formation of by-products and the relevant treatment aimed at preventing environmental pollution. Accordingly, modern techniques for increasing waste-to-energy efficiency and integrating the concept of circular economy and substitutability are analyzed from this perspective. Along with an analysis of modern scientific achievements in this area, practical examples of the implementation of technologies in European countries are given, with an emphasis on the obvious advantages, both economic and environmental. [ABSTRACT FROM AUTHOR]

Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As it turns out, WEEE recycling produces further waste, called WEEE secondary waste, which still contains valuable metals such as gold, silver, and copper. This study assessed the economic viability of recovering these metals and identified the most promising targets and approaches. WEEE secondary waste produced at a plant in southern Europe was sampled and examined for this purpose. The study methods included an ANOVA (analysis of variance) and an OCCP (orthogonal central composition plan). Over 90% gold, silver, and copper extraction was achieved with hydrochloric acid leaching in sodium hypochlorite with sodium chlorite as an oxidizing agent at 60 °C. The significance of the variation in the response for each factor, calculated using the Yates algorithm, demonstrates that by excluding sodium chloride and optimizing the doses of hydrochloric acid and sodium hypochlorite, gold can be selectively recovered through the leaching process. The scenario of HCl (2.5M)/NaClO (5%) leaching results in the maximum extraction effect of Au (91.6%) at the lowest concentrations of Ag and Cu (37–44%). [ABSTRACT FROM AUTHOR]

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (

The main objective of this work was to improve the technological scheme of oil refinery wastewater treatment. Replacment of the expensive filter section in a refinery plant by coagulation in order to increase effectiveness of the process at lower cost was investigated. This research has proven that Ca(OH)2 and Al2(SO4)3 were effective in treatment of oil wastewater. Central Composite Design was applied to two factors, the Al2(SO4)3 dosage and pH. Under optimum conditions effect of removal of Turbidity did reach 100 %, Total hydrocarbons 90 % and COD 70 %. Concentration of Total hydrocarbons in wastewater after treatment were below Limits for sewerage. Prevailing mechanism for coagulation was charge neutralization, associated with deposition of positively charged aluminum hydroxide onto negatively charged particles. Applying of cogulation will let significantly reduce operating expenses up to 5,436.35 €/year, at the same efficiency, due to replacing expensive filtration processes with cost of 102,600.00 €/year.