Preparatiοn οf pοrοus hydrοxyapatite-metakaοlin geοpοlymer granules fοr adsοrptiοn applicatiοns using pοlyethylene glycοl as pοrοgen agent and sοdium dοdecyl sulfate as aniοnic surfactant.

This study investigated the elaboration of novel porous absorbent granules by mixing powdered hydroxyapatite, metakaolin, sodium metasilicate, polyethylene glycol, and sodium dodecyl sulfate (SDS), an anionic surfactant. The effect of sodium dodecyl sulfate (SDS) was then studied by introducing it as a powder to the powdered mixture or dissolved into the granulation fluid. Characterization of the granules indicated that the incorporation of SDS dissolved in the granulation fluid into the G-PEG granules improved their specific surface area (97.9 m2/g) and porosity, resulting in a synergistic increase in the adsorption of crystal violet and methylene blue dyes compared to G-PEG granules and hydroxyapatite or metakaolin geopolymer alone. Moreover, the granules exhibited satisfactory compressive strength of 0.81 MPa, making them suitable for large-scale adsorption columns. Finally, the regeneratiοn prοcess οf the granules was modeled and optimized by using surface response methodology based on Box-Behnken design. The granules cοuld be regenerated fοr eight cycles under οptimum cοnditiοns οf acetic acid cοncentratiοn οf 0.72 mοl/L, a temperature οf 323 K, and a cοntact time οf 173.22 min, withοut a significant lοss in the adsοrptiοn capacity οr degradatiοn οf the granules. These results suggest that the pοrοus granules prepared in this study have pοtential tο be used in industrial wastewater treatment.

Central composite design applied to paracetamol degradation by heat-activated peroxydisulfate oxidation process and its relevance as a pretreatment prior to a biological treatment.

In this study, the degradation of paracetamol (PCT) by thermo-activated peroxydisulfate (PDS) and the feasibility of coupling thermo-activated peroxydisulfate to activated sludge culture were examined. The effect of the relevant parameters on the thermo activated peroxydisulfate process, namely temperature, PDS concentration, initial pH and initial PCT concentration was investigated. As observed, the solution pH did not have a significant effect on the PCT degradation. The temperature increased the degradation of PCT, while an increase of the initial PCT concentration impacted negatively its degradation yield. The PDS concentration showed an optimal value of 8 mM. The operating parameters were then optimized by using a central composite design (CCD). After performing a screening of the various factors, response surface analysis led to the following optimal conditions for the yield of PCT degradation: 0.33, 5 mM, pH = 6 and 68°C for the initial PCT concentration, the initial peroxydisulfate concentration and the temperature respectively, leading to the removal of 94.2% of PCT. Under these conditions, the BOD5/COD ratio increased from 0.008 initially to 0.34 after 10 h. Showing a significant improvement of the biodegradability; consequently and even if the limit of biodegradability (0.4) was not achieved, a biological treatment could be promisingly considered.

Paracetamol degradation by photo-activated peroxydisulfate process (UV/PDS): kinetic study and optimization using central composite design.

In this study, peroxydisulfate (PDS) was successfully activated by UV-irradiation for the degradation of paracetamol (PCT) frequently detected in the environment. Results showed that increasing the initial PDS concentration from 5 to 20 mM promote the removal of PCT from 49.3% to 97.5% after 240 min of reaction time. As the initial PCT concentration increased from 0.066 to 0.132 mM, the degradation efficiency of PCT decreased from 98% to 73% after 240 min of reaction time, while the optimal pH was found to be 6. It is apparent that the degradation rate of PCT was favored by the lamp power regardless of the initial PCT concentration, for 0.132 mM of PCT, the degradation efficiency increased from 73% to 95% when the lamp power increased from 9 to 30 W, respectively. The kinetic of degradation of the PCT was described by a pseudo-second order kinetic model. The model obtained by central composite design led to the following optimal conditions for PCT degradation: 0.132 mM initial PCT concentration, 20 mM PDS dose, pH solution 6 and lamp power 30 W led to the removal of 92% of PCT at 25 °C within 240 min of reaction time.