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In this study, porous activated carbon was produced from coffee waste and used as an effective adsorbent for the removal of humic acid (HA) from seawater and methyl orange (MO) dye from aqueous solutions. Phosphoric acid H3PO4 was used as an activating agent for the chemical activation of these agricultural wastes. The characterization of the activated carbon obtained using a scanning electron microscope (SEM), Fourier-transform infrared (FTIR) spectroscopy analysis, X-ray diffraction (XRD) and the Brunauer–Emmett–Teller (BET) method revealed that the activated carbon products exhibited high porosity and the formation of various functional groups. The effects of different parameters were examined using batch adsorption experiments, such as the adsorbent masses, pH, initial pollutant concentration and contact time. The results show that the performance increased with an increased adsorbent mass (up to 0.25 g/L) and decreased initial concentration of the adsorbent tested. On the other hand, this study clearly showed that the adsorption efficiency of the MO on the raw spent coffee grounds (SCGs) waste was around 43%, while no removal was observed for the humic acid. The experiments demonstrated that the activated carbon synthesized from the used coffee grounds (the efficiency was compared with commercial activated carbon (CAC) with a difference of 13%) was a promising alternative to commercially available adsorbents for the removal of humic acid from seawater. To understand and elucidate the adsorption mechanism, various isothermal and kinetic models were studied. The adsorption capacity was analyzed by fitting experimental data to these models. The experimental data for methyl orange dyes were analyzed using Langmuir and Freundlich isothermal models. The Freundlich isotherm model provided a superior fit to the equilibrium data, as indicated by a higher correlation coefficient (R2) than that of the Langmuir model. The maximum adsorption was observed at pH 3. The Freundlich adsorption capacity was found to be 333 mg/g adsorbent. The PAC showed a high adsorption capacity for the MO and HA. The PAC showed the highest adsorption capacities for the HA and MO compared with the other adsorbents used (SCGs and CAC) and would be a good material to increase the adsorption efficiency for humic acid removal in the seawater pretreatment process. In addition, the prepared AC BET surface area was 520.40 m2/g, suggesting a high adsorption capacity. This makes the material potentially suitable for various applications that require a high surface area. These results indicate that high-quality sustainable activated carbon can be efficiently produced from coffee waste, making it suitable for a wide range of adsorbent applications targeting various pollutants. [ABSTRACT FROM AUTHOR]

The main objective of this study was to demonstrate the efficiency and to optimize the operating conditions of photodegradation of paracetamol in the presence of suspended titanium dioxide catalyst in a photoreactor. An experimental design study was carried out using central composite design modelling. Optimization was applied to the tubular reactor under fixed photonic flux with radiation from two 24-watt UV-A lamps. The optimal values of the operating parameters were found to be pH of 7.288, TiO2 concentration of 0.9932 g·L-1 and paracetamol initial concentration of 15 mg·L-1. The paracetamol degradation rate approached 98.46% under optimal conditions. Modelling of the system led to a second-degree polynomial. Regression analysis gave an R² value of 0.977 which meant good agreement between the experimental results and the predicted values. An interaction was demonstrated between the catalyst and the operating parameters (pH, CPara and CTiO2) as well as between the model pollutant concentration and the pH had an insignificant effect on the yield compared to that of the quantity of the catalyst and the initial pollutant concentration. [ABSTRACT FROM AUTHOR]

The non-biodegradability of textile wastewater is mainly due to the presence of synthetic dyes. Resistance to bacterial degradation led to the development of new techniques where solar photocatalysis appears to be the best method for this type of application. methylene blue (MB) degradation was studied in TiO2and ZnO aqueous suspension using solar energy in a tubular reactor. This study was conducted to evaluate the performance of the prototype and explore the feasibility of this concept for solar photocatalytic oxidation. The main objective of this work was to compare the efficiency of two types of catalysts, which are titanium dioxide (TiO2) and zinc oxide (ZnO). The use of TiO2as a catalyst enables a good degradation of MB which can achieve a disposal rate of 98% after 270 min with a TiO2concentration of 0.75 g/L. The same removal rate can be achieved by ZnO but for a much smaller concentration which was 0.025 g/L after 140 min. [ABSTRACT FROM AUTHOR]

Nowadays, water availability and quality represent a major challenge. In 2050, the United Nations Organization predicts that 44% of the world population will face severe water scarcity. Countries located in sub-humid and semi-arid regions of the world will be especially concerned for this problem, because of their low supply of rainwater. The aim of this study is to suggest the disinfection treatment by irradiation as a complement wastewater treatment to obtain a safe microbial quality of water and permit its reuse. This last is limited to 1.000 CFU/100 ml (i.e. equivalent to 3 log) of fecal coliforms by the Algerian and WHO standards. The experiments were conducted to disinfect wastewater by UVA, UVC, and solar radiation. The UVA and UVC disinfection treatments were carried out using an experimental bench composed of three flat-bottom flasks and three Erlenmeyers of 2 L each. The solar disinfection treatment was experimented using a 30 L-tubular photoreactor in a stationary and a dynamic flow. The disinfection results indicate a reduction in 2.47 log of total coliforms, 3 log reduction of fecal coliforms, 2.67 log reduction of streptococci, 3.17 log reduction of staphylococci, 0.08 log reduction of yeasts, 0.19 log reduction of molds, and a reduction of 1.17 log of sulfite-spores. [ABSTRACT FROM AUTHOR]

The wastewater reuse, especially for irrigation, requires a safer microbial quality. However, the tertiary treatment is often nonexistent, especially in developing countries where, unfortunately, wastewater treatment needs to be more systematic. Solar water disinfection processes could be appropriate treatments for improving the microbial quality of the wastewater reuse. This study evaluates the effectiveness of both solar photolysis and solar photocatalysis processes in disinfecting secondary-treated wastewater recovered from an activated sludge wastewater treatment plant where the disinfection treatment is not applied. The best parameters of the solar disinfection processes were determined. The experiments were conducted in a bench test composed of 4 flat-bottom flasks with a volume of 2 L each. Then, the disinfection efficiency of both processes was evaluated by a comparative study where 250 Wh/m² of UV radiation was cumulated. The disinfection efficiency of studied pathogenic (1) total coliforms, (2) fecal coliforms, (3) streptococci, (4) staphylococci, (5) sulfite-reducing spores, and (6) fungi ranged from 0.86-Log to 3.35-Log reduction. At last, an innovative static plan photoreactor of 50 L allowed reproducing the positive effect of the solar wastewater disinfection. After 8 h of solar exposure duration and a cumulative UV radiation of 360 Wh/m², results showed a complete disinfection of all studied pathogenic below the limit detection of the microbial analysis, except of sulfate-reducing spores. [ABSTRACT FROM AUTHOR]