Search

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 aim of this study is to investigate the atenolol (ATL) degradation in aqueous suspension using commercial ZnO photocatalysts under solar irradiation. Effects of various operating parameters such as the ZnO dosage (0.025 to 0.075 g L−1), as well as pH ranges (3–12), and the ATL concentration (5–30 mg L−1) were also studied in a batch system. Results show that alkaline medium favoured the photocatalytic degradation of ATL (pH~7) and the best value of ZnO dosage occurred in 0.075 g L−1. Also, the removal rate increased with increasing ATL concentration. Kinetic data indicated that the photocatalytic kinetics followed the second-order model at high concentration of ATL, third-order model at low concentration, and first order model when adjusted pH. The second-order rate constant (k2) increases from 0.064 to 0.13 L mg−1 mn−1 when ZnO dosage increases from 0.025 to 0.2 g L,−1 respectively. As well, the pH rises from 3 to 7 the first-order rate constant (k1) increases from 0.35 to 1.56 mn−1. Then, at pH = 12 the rate constant (k1) decreases to 0.74 mn−1. The biodegradability, based on the BOD5 to COD ratio, increased with the increased photocatalysis time. [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 results of a feasibility study are presented on the use of a polystyrene (PS) organic membrane as a photocatalyst support in the degradation of organic pollutants in aqueous solution. Methylene blue (MB) was employed as a model dye and commercial titanium dioxide (TiO2) was used as a photocatalyst. The MB dye which is resistant to direct photolysis especially at high concentrations was successfully eliminated by TiO2fixed on the PS membrane in aqueous dispersion under solar irradiation. Photodegradation results of MB showed that the film with 10 wt% TiO2exhibited a remarkable ultraviolet (sun light) photocatalytic activity over 5 h, with 68% of the pollutant being degraded. This is similar to a TiO2slurry system. The photocatalytic degradation obeyed pseudo-first-order kinetics at low initial MB concentration. The optimum pH for efficient removal of dye was found to be 11. An increase in initial dye concentration decreased the degradation rate. The applicability of Langmuir–Hinshelwood kinetic equation revealed that the degradation of MB occurred mainly on the surface of the photocatalyst. The concept and results provide a promising platform for fabricating highly efficient organic photocatalytic membranes for water treatment. [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]

Photocatalytic TiO2-PVDF/PMMA nano-composites flat sheet membranes were fabricated by phase inversion and then employed in a crossflow filtration pilot to remove model pollutants of various sizes and charge from aqueous solution. The dope solution contained a mixture of PVDF and PMMA as polymers, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) as additives, triethyl phosphate (TEP) as green solvent and TiO2 as immobilized photo catalyst. After undergoing characterization tests such as SEM morphology thickness, porosity, contact angle and water permeability, the membranes were used to eliminate the model pollutants from synthetic aqueous solution. The impact of the operating conditions (i.e., pH, pressure and initial pollutant concentration) and composition of the doping solution on the performance and photocatalytic and antifouling activity of the membranes was investigated. The results showed that Congo Red and Tartrazine despite their small size were rejected at 99% and 81%, respectively, because of their negative charge, while Ciprofloxacin, which is larger than Tartrazine but of neutral charge, crossed the membrane. The permeability did not decrease with a decline in pollutant concentration but diminished when the pressure increased and was reduced by more than half for wastewater. [ABSTRACT FROM AUTHOR]