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Nowadays Light Emitting Diodes (LEDs) are widely utilized. They are applied as backlighting in Liquid Crystal Displays (LCD) and TV sets or as lighting equipments in homes, cars, instruments and street-lightning. End of life equipments are containing more and more LEDs. The recovery of valuable materials -such as Ga, Au, Cu etc. -from the LEDs is essential for the creating the circular economy. First task is the development of a proper recycling technology. Most of the researchers propose fully chemical or thermal-chemical pathway for the recycling of LEDs.In the meantime our approach based on the thorough investigation of the structure and composition of LEDs, and shown in this paper, is the combination of mechanical and chemical techniques in order to recover more valuable products, as well as to facilitate the mass transfer. Our laboratory scale experiments are introduced, the final aim of which is Ga recovery in accordance with our above approach. It was experimentally proved that the LED chips contain Ga and can be recovered by mechanical processes along with copper-product. Ga is presented on the surface of the chips in GaN form. Mechano-chemical activation in high energy density stirred medium mill and the following acidic leaching resulted in the enrichment of 99.52% of gallium in the pregnant solution.

Abstract The main point of this research is to assess the applicability of condensed molasses soluble (CMS), which is an organic by-product of lysine fermentation, as an environmentally friendly complexing agent in rhizofiltration of heavy metal contaminated acid mine drainage (AMD). First, the ecotoxicological properties (growth inhibition, seed germination) of CMS were examined with often applied indicator plant species such as duckweed (Lemna minor) and lettuce (Lactuca sativa) so as to define the possible applicable CMS concentration. Then the heavy metal accumulation and translocation properties of root accumulator plant species, i.e. common reed (Phragmites australis) and sedge (Carex flacca), were studied to optimize CMS concentration for rhizofiltration. Due to the CMS application, significant increase in bioaccumulation was detected in the case of every examined heavy metal (As, Cd, Cu, Pb and Zn) at the end of the experiment. Results also showed that CMS increased the heavy metal concentration in shoots, but did not affect the root accumulation characteristics of the plants. Furthermore, CMS treated plants accumulated heavy metals at higher rates in their roots compared to control. The results suggest that CMS is a viable additive and a complexing agent to aid rhizofiltration of heavy metal contaminated AMD.

The poultry (broiler) industry is continuously increasing all over the world, therefore, the amount of waste generated in these facilities is also increasing. As a consequence of the above mentioned, the more efficient conversion of chicken manure to organic fertilizer is a key problem. The aims of the study are to investigate the changes in temperature and moisture content during composting of chicken manure in the oval tank fermentation system and to create a model for the evaluation of the performance of biodegradation processes. The moisture and temperature distribution models of the oval tank were created in Hydrus software. The results showed that the oval tank fermenter can be divided into two main zones. In the first zone, where the rate of biodegradation was relatively high, a heterogeneous temperature zone was found with continuously decreasing moisture content. The second zone was more homogenous in both temperature and moisture content. This stage represents the weak fermentation part of the technology and results in an elongated post fermentation section. Furthermore, statistically significant correlations were found between composting key parameters, such as ammonium content with temperature and organic matter content with organic nitrogen content. It was also concluded that the exact location of the manure turning and chopping mechanical system (MTCM) used for aeration had a high effect on the composting processes, as well as on the quality parameters of the mature compost.

The world demands more and more energy due to the continuous population increase. In parallel, high organic and nutrient contents of wastewater streams are generated from anthropogenic activities like urbanization, industrialization, and agricultural practices. The continuous discharge of these wastewater streams into water bodies has been considered responsible for oxygen depletion and eutrophication in the environment. Integrating microalgae cultivation into wastewater treatment can be a promising solution to produce renewable energy while removing pollutants. In contrast to several review articles published about microalgae cultivation on different wastewater streams, the current review is focusing mainly on microalgae-based wastewater treatment on agricultural waste streams. Hence, first of all, the main characteristics of different agricultural streams will be described, then microalgal consortia cultivation, as well as monoculture strains, will be evaluated. Moreover, the photobioreactor systems for agricultural wastewater treatment will also be summarized. Finally, harvesting methods for microalgae recovery will be presented.