Insights into the S-shaped sorption isotherms and their dimensionless forms

Isotherms are of paramount importance for the interpretation of adsorption and ion exchange mechanisms and the design of separation and catalytic processes. Although the literature on sorption isotherms is rich, most of experiments and models employed are limited to systems that obey simple equilibrium isotherms, such as linear, favorable (convex-upward) or unfavorable (concave-upward). This paper deals with the rather overlooked S-shaped isotherms and their dimensionless forms, which are of great importance for the modeling of separation processes and interpretation of equilibrium data. A review on the physical significance and applications of S-shaped isotherms in adsorption and ion exchange process is also presented

The Impact of Religious Beliefs and Practices on Coping with Health Challenges Posed by Covid-19

In the midst of the Covid-19 pandemic, the aim of the present study was to investigate to what extent the undergraduate students of the Department of Dentistry, Aristotle University of Thessaloniki, felt the need to come closer to their own religiosity, spirituality, or faith. Materials and methods: Empirical research was conducted by means of an anonymous questionnaire, comprising demographics and items focusing on religiosity, spirituality, and faith. The survey results were processed using “MICROSOFT EXCEL IBM SPSS STATISTICS 24” statistical processing software. Results:  To overcome health dilemmas, the wide majority of students did not focus on religious & spiritual practices (70% & 66.7%) while at the same time, their religiosity & spirituality was not enhanced (74% & 78%). However, for the same period, 53% of the students stated that their faith was enhanced. Conclusions: While overall students’ religiosity & spirituality indicators were low, for the same period they stated that their faith in overcoming health distress was strengthened, which triggers new questions and prompts further research in the field of humanities.&nbsp

Photochemical degradation of organic pollutants in wastewaters

In the present work, the photochemical treatment of a synthetic wastewater in a batch recycle photochemical reactor using ultraviolet irradiation (254 nm, 6 W), hydrogen peroxide and ferric ions was studied. Reactor volume was 250 mL with 55.8 mL of irradiated volume in the annular photoreactor. The synthetic wastewater was composed mainly of organic carbon. The effect of initial total carbon (136-1080 mg L-1), initial H2O2 amount (1332-5328 mg L-1), pH, and Fe(III) presence (2-40 ppm), on total carbon (TC) removal was studied. Each experiment lasted 120 min, and the process was attended via pH and TC concentration. Direct photolysis in the absence of any oxidant had practically no effect on TC removal. Regarding the effect of initial TC concentration in the wastewater keeping the same initial hydrogen peroxide concentration (2664 mg L-1), it was observed that for 136-271 mg L-1 TC, around 60% TC removal was achieved, while when initial TC was increased at 528 mg L-1, the TC removal observed decreased to 50%. For a further increase in TC at 1080 mg L-1, TC removal dropped to 14%. Initial pH adjustment of the wastewater resulted in slight variations of the TC removals achieved. Finally, adding Fe(III) in the process was beneficial in terms of TC removal obtained. Particularly, the addition of 40 ppm Fe(III) in the presence of 2664 mg L-1 H2O2 and initial TC equal to 528 mg L-1 increased the TC removal from 50% to 72%

Photocatalytic treatment of a synthetic wastewater

This work aimed at investigating the photocatalytic treatment of a synthetic wastewater using UV light (254 nm, 6 W), TiO2 catalyst and H2O2 in a batch recycle annular photoreactor. The total volume of the solution was 250 mL while the irradiated volume in the annular photoreactor with 55.8 mL. Each experiment lasted 120 min and samples were sent for Total Carbon and HPLC analysis. The stock wastewater had initial total carbon 1118 mg L-1. The effect of the presence of phenol in the wastewater on total carbon (TC) removal was also studied. It was shown that the photocatalytic treatment was effective only when initial TC was decreased to 32 mg L-1, whereas the optimum TiO2 concentration was 0.5 g L-1, leading to a TC removal up to 56%. For the same initial carbon load, the optimum H2O2 concentration was found to be 67 mg L-1 resulting in 55% TC removal. Combining, however, TiO2 and H2O2 did not lead to better performance, as 51% TC removal was observed. In contrast, when initial carbon in the wastewater was partially substituted by phenol, the combination of catalyst and hydrogen peroxide was beneficial. Specifically, when 10 ppm of phenol were added keeping the same initial TC concentration, UV/TiO2 treatment resulted in 46% TC removal and 98% phenol conversion, whereas using additionally H2O2 led to 100% phenol conversion after 45 minutes and 81% TC removal

Photocatalytic treatment of organic pollutants in a synthetic wastewater using UV light and combinations of TiO2, H2O2 and Fe(III)

In this study, the photocatalytic treatment of an organic wastewater with/without phenolic compounds by means of ultraviolet irradiation, titanium dioxide and hydrogen peroxide was examined in an annular photoreactor. Specifically, the effect of initial total carbon concentration, catalyst loading and H2O2 amount on the removal of total carbon was first examined in the case of a synthetic organic wastewater. The influence of partial carbon substitution by phenol, 2-chlorophenol, 2,4-discholophenol, trichlorophenol, and 4-nitrophenol on total carbon removal and target compounds’ conversion was studied keeping constant the initial organic carbon load. It was shown that the process applied was effective in treating the wastewater for initial total carbon 32 mg L-1, 0.5 g L-1 TiO2, and 66.6 mg L-1 H2O2. Applying UV/TiO2 and UV/H2O2, 58% and 53% total carbon removals were achieved, respectively, but combining TiO2 and H2O2 did not result in a better performance in the case of the synthetic wastewater without any phenolic compounds. In contrast, when a phenolic compound was added, the addition of H2O2 was beneficial, eliminating the differences observed from one phenolic compound to another. The total carbon removals observed were lower than the corresponding final conversions of the target phenolic compounds. Finally, the electric energy per order values were calculated and found to range in 52–248 kWh/m3/order, being dependent from the process applied and the phenolic compound present in the wastewater

The Role of the Religion Vis-à-vis the 'Health Challenges' of Covid-19

Αim: In the midst of the Covid-19 pandemic, the aim of the present study was to investigate to what extent the undergraduate students of the Department of Dentistry, Aristotle University of Thessaloniki felt the need to come closer to their own religiosity, spirituality or faith. Materials and methods: Empirical research was conducted by means of an anonymous questionnaire, comprising demographics and items focusing on religiosity, spirituality and faith. The results of the survey were processed using MICROSOFT EXCEL IBM SPSS STATISTICS 24 statistical processing software. Results:  To overcome health dilemmas, the wide majority of  students did not focus on religious & spiritual practices (70% & 66.7%) while at the same time their religiosity & spirituality was not enhanced (74% & 78%). However, for the same period 53% of the students stated that their faith was enhanced. Conclusions-Discussion: While overall students’ religiosity & spirituality indicators were low, for the same period they stated that their faith in overcoming health distress was strengthened, which triggers new questions and prompts further research in the field of humanities.&nbsp

TI2O3/TIO2-ASSISTED SOLAR PHOTOCATALYTIC DEGRADATION OF 4-TERT-BUTYLPHENOL IN WATER

Colored Ti2O3 and Ti2O3/TiO2 (mTiO) catalysts were prepared by the thermal treatment method. The effects of treatment temperature on the structure, surface area, morphology and optical properties of the as-prepared samples were investigated by XRD, BET, SEM, TEM, Raman and UV–VIS spectroscopies. Phase transformation from Ti2O3 to TiO2 rutile and TiO2 anatase to TiO2 rutile increased with increasing treatment temperatures. The photocatalytic activities of thermally treated Ti2O3 and mTiO were evaluated in the photodegradation of 4-tert-butylphenol (4-t-BP) under solar light irradiation. mTiO heated at 650 C exhibited the highest photocatalytic activity for the degradation and mineralization of 4-t-BP, being approximately 89.8% and 52.4%, respectively, after 150 min of irradiation. The effects of various water constituents, including anions (CO2 3 , NO3, Cl and HCO 3 ) and humic acid (HA), on the photocatalytic activity of mTiO-650 were evaluated. The results showed that the presence of carbonate and nitrate ions inhibited 4-t-BP photodegradation, while chloride and bicarbonate ions enhanced the photodegradation of 4-t-BP. As for HA, its effect on the degradation of 4-t-BP was dependent on the concentration. A low concentration of HA (1 mg/L) promoted the degradation of 4-t-BP from 89.8% to 92.4% by mTiO-650, but higher concentrations of HA (5 mg/L and 10 mg/L) had a negative effect

Impact of Economic Crisis on Passenger Transportation – Case of Travelling to the Greek Mainland from Crete

The Greek economic crisis of 2009 onwards has affected all aspects of social and economic life of the country, including transportation. The present study focuses on the impact of economic crisis on the long distance transportation between the island of Crete in Greece, the largest Greek island and one of the largest in the Mediterranean Sea, and the Greek mainland. A questionnaire survey was used to investigate the opinions of the Cretans on the way the economic crisis influenced their transportation to the Greek mainland. The results of the survey show that the frequency of the Cretans’ travels was significantly limited, owing to the increased direct or indirect associated cost, due to the economic crisis. Especially for those who struggled to make ends meet, the transportation to the mainland dropped to the bare essentials. Furthermore, the respondents deemed that the&nbsp;deregulation of the Greek maritime and airline markets was also to blame for the high fares, thus they favoured a regulated public transport sector and were against privatization. Inevitably, financially vulnerable individuals were the most preoccupied with these issues. A feeling of isolation and exclusion was revealed by the sample on occasions when the scheduled trips were cancelled by the operators due to exogenous parameters.</p

Effective photochemical treatment of a municipal solid waste landfill leachate

This work aimed at studying the photochemical treatment of a landfill leachate using ultraviolet light, hydrogen peroxide, and ferrous or ferric ions, in a batch recycle photoreactor. The effect of inorganic carbon presence, pH, initial H2O2 amount (0–9990 mg L-1) as well as Fe (II) (200–600 ppm) and Fe(III) (300–700 ppm) concentrations on the total carbon removal and color change was studied. Prior to the photochemical treatment, a pretreatment process was applied; inorganic nitrogen and inorganic carbon were removed by means of air stripping and initial pH regulation, respectively. The leachate sent subsequently for photochemical treatment was free of inorganic carbon and contained only organic carbon with concentration 1200±100 mg L-1 at pH 5.1–5.3. The most favorable concentrations of H2O2 and ferric ions for carbon removal were 6660 mg L-1 and 400 ppm, respectively. Adjusting the initial pH value in the range of 2.2–5.3 had a significant effect on the organic carbon removal. The photo-Fenton-like process was more advantageous than the photo-Fenton one for leachate treatment. By applying the most favorable operating conditions, 88.7% removal of total organic carbon, 100% removal of total inorganic carbon, 96.5% removal of total nitrogen, and 98.2% color removal were achieved

Catalytic oxidation of methylene blue by use of natural zeolite-based silver and magnetite nanocomposites

This work reports the synthesis of natural zeolite-based silver and magnetite nanocomposites and their application for the catalytic oxidation of methylene blue in water. The zeolite was impregnated with 5.5 wt.% Fe in the form of magnetite nanoparticles with size of 32 nm, and with 6.4 wt.% Ag in the form of silver oxide and metallic silver nanoparticles with sizes of 42 and 20 nm, respectively. The results showed that physical adsorption contributed to the removal of methylene blue by 25−36% and that Fe3O4@NZU is superior to Ag2O@NZU and Ag0@NZU, leading to 55% removal without oxidant and 97% in the presence of H2O2. However, there is no evidence of significant mineralization of methylene blue. The application of reaction rate models showed that the reaction order changes from zero to first and second order depending on the H2O2 concentration