Issue 2 (In progress)

250 million people worldwide suffer from visual impairment. 64% of them wear glasses. More than 80 percent of all eyeglasses worn today have plastic lenses. Plastic lenses made of polycarbonate discs are created through the process of machining which requires the use of a coolant. The ensuing wastewater contains chips, water, and coolant. In the studied facility, the chips are separated by filtration. Water and coolant are returned to the machine tool. Due to the low particle weight some of the plastic dust flotates and creates foam. If there is too much foamed dust, a skimmer is added. In order to avoid machine damage and product quality deterioration, the mixture in circulation is changed every 24 hours. For the purpose of the study, wastewater was sampled from the plastic lenses facility. It was characterized by a high COD value of 11 200 - 20800 mg/L, a turbidity of 260-870 NTU, and a colour of about 200 mg/L. Wastewater with these parameters should not be discharged into the sewage system. For their treatment, a coagulation process (PAX 18 and PAX XL 19 H, Tanfloc SG) and Fenton process were applied. The application of aluminum coagulants resulted in a maximum reduction of COD of 55%. Maximum COD reduction after the Fenton process was 50.7%.

Anthracene and phenanthrene belong to a group of persistent environmental contaminants called PAHs. Evaluation of the structure of two selected PAHs i.e. anthracene and phenanthrene on their resistance to destruction by UV-activated PDS was the aim of this study. The authors focused on two aspects of this problem: - the role of the so-called ‘bay-region’, in the structure of phenanthrene, during PDS/UV oxidation - formation of substituted forms of these PAHs in the absence and presence of three nitrogen-containing compounds i.e. ammonia and nitrite or nitrate ions. Even though phenanthrene and anthracene have the same molecular formula, the difference in their ring assessment influences their degradability. Considering all the results, in all the cases anthracene was degraded faster and/or had a higher degradation rate. That proves phenanthrene to be more stable and resistant for degradation however comparison of PDS/UV systems vs. UV– irradiation alone confirms that the addition of PDS accelerates the degradation of anthracene and phenanthrene. Comparison of PDS/UV with the addition of three different nitrogen-containing compounds showed a significant difference between anthracene and phenanthrene. In the experiments with phenanthrene were observed additional peaks with an absorption maximum between 230-240 cm-1 which is characteristic of the nitro-group. Based on their absorption maximum and the addition of nitrogen-containing compounds, emerging by-products are assumed to be nitro-derivatives of phenanthrene. The results of GC/MS analysis suggest the possibility of formation of many compounds which can be formed from phenanthrene and are embedded on its skeleton. These analyzes also suggest the rearrangement of phenanthrene’s aromatic rings and formation new compounds.

Photocatalytic degradation for wastewater treatment is a method that has recently attracted attention. In this research, a synthesized composite of Fe3O4/SiO2/NiO with magnetic properties was used for the photocatalytic degradation of methylene blue dye under UV light. Furthermore, the composites were characterized using XRD, FTIR, BET surface area, SEM-EDS, VSM, and UV-DRS. The results showed that the Fe3O4/SiO2/NiO composite is magnetic with a saturation magnetization of 53.84 emu/g. The Fe3O4/SiO2/NiO composite has a surface area of 128.8 m2/g, large than Fe3O4 and Fe3O/SiO2. The Fe3O4/SiO2/NiO composite has a band gap of 2.83 eV. The photocatalytic activity of Fe3O4/SiO2/NiO composite against the methylene blue dye exhibited high degradation efficiency reaching 98.51 %. The pseudo-first-order is appropriate to describe the kinetics model of photocatalytic degradation on methylene blue dye. The decrease in the degradation efficiency of the Fe3O4/SiO2/NiO composite after 5 times for the photocatalytic degradation of methylene blue dye from 98.02 % to 94.97 % indicates that the catalyst has high stability. Considering these results, the Fe3O4/SiO2/NiO composites could be used as a potential catalyst in industrial wastewater.