Removal of aqueous Clopyralid by Photoctalytic-ozonation process on Activated carbon under solar radiation: Catalyst characterization and kinetic study

Solar photocatalytic ozonation has been used to oxidize the herbicide clopyralid in aqueous solution. Activated carbon used as a catalyst was characterized by Scanning Electron Microscopy (SEM) images showed the presence of irregular cavities and pores, which have different sizes and shapes, with a great surface area of BETand a high pHpzc. The adsorption kinetics was found to follow the pseudo-second-order kinetic mode. Catalyst stability was tested by means of consecutive reuse cycles. After five cycle of reuse the adsorption efficiency reached 75% of the clopyralid removal.Clopyralid elimination kinetic by direct ozonation has been studies. The system O3/AC/Daylight significantly improves clopyralid and mineralization rate abatement if compared to runs conducted in the absence of radiation and/ or activated carbon. Clopyralid total abatement was achieved in less than 30 min when 0.5 g/L of activated carbon and under solar radiation (300-800 nm) were used. Thus, TOC removal in 180 min treatments increased from 20 to about 90 % in O3 and O3/OSAC/Daylight, respectively, under similar operating conditions

Thermal behaviour of impregnated olive stones with phosphoric acid via TGA-MS

This study aims to investigate the thermal behaviour of raw and phosphoric acid impregnated olive stones via coupled thermogravimetric analysis-Mass spectrometry (TGA-MS) during pyrolysis. The impregnated material was prepared at three H$_{3}$PO$_{4}$/precursor weight ratio of 0.5; 1 and 1.5; for various impregnation time of 3, 6 and 9 h, which was then subjected for thermal analysis. TGA profiles were obtained under dynamic conditions in temperature range 25 °C to 750 °C with a heating rate of 10 °C/min, using pure nitrogen as an inert gas. Thermal degradation of olive stones was observed in three stages namely dehydration, active and passive pyrolysis. Two-steps degradation of raw olive stone occurred, whereas the impregnated material displayed only one step. Addition of phosphoric acid sharply reduced the onset temperature of the main decomposition step. Onset temperatures decreased with increasing rate or time of impregnation. It could conclude that 3 h is sufficient as time of impregnation for activated carbon production. Examination of the main gas products were carried out using coupled TGA-MS. The principal permanent gases detected were H$_{2}$, H$_{2}$O, CO, CO$_{2}$ and the light hydrocarbons C$_{2}$H$_{6}$ and CH$_{4}$. Different kinetic scenarios of raw and impregnated olive stones were observed. The above results should be useful to understand the pyrolysis mechanism of phosphoric acid impregnated olive stone for improving activated carbon production

Hydrogen production by methane decomposition over Ni-doped activated carbons: effect of the activation method

Ni supported over activated carbon (AC) based on olive stones were tested for methane decomposition to produce hydrogen. Physical (by $\mathrm{H}_{2}\mathrm{O}$) and chemical (by $\mathrm{H}_{3}\mathrm{PO}_{4}$) activations were compared. Kinetic parameters of methane decomposition were determined depending on Ni load, methane partial pressure and reaction temperature. The catalysts were characterized before and after reaction by $\mathrm{N}_{2}$ adsorption, X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The catalysts showed good initial activities that increased with temperature and nickel load, reactivity decreased with time. The reaction orders were 0.63 and 0.74 and the activation energies were 122 and 139 kJ/mol for physically and chemically activated carbon, respectively. BET surface areas and pore volumes decreased dramatically after reaction due to the deposit of carbon on the support. Ni stayed under its metallic form on the physically AC whereas it was mainly present as $\mathrm{Ni}_{12}\mathrm{P}_{5}$ over the chemically activated one. TEM characterization revealed the formation of well-organized carbon nano-onions surrounding Ni particles on the physically activated carbon. Nano-onions were not formed around $\mathrm{Ni}_{12}\mathrm{P}_{5}$ particles in the chemically activated carbon. The physical activation allowed the synthesis of catalysts with a better stability for methane conversion than what chemical activation would allow

Thermal behaviour of impregnated olive stones with phosphoric acid via TGA-MS

This study aims to investigate the thermal behaviour of raw and phosphoric acid impregnated olive stones via coupled thermogravimetric analysis-Mass spectrometry (TGA-MS) during pyrolysis. The impregnated material was prepared at three H$_{3}$PO$_{4}$/precursor weight ratio of 0.5; 1 and 1.5; for various impregnation time of 3, 6 and 9 h, which was then subjected for thermal analysis. TGA profiles were obtained under dynamic conditions in temperature range 25 °C to 750 °C with a heating rate of 10 °C/min, using pure nitrogen as an inert gas. Thermal degradation of olive stones was observed in three stages namely dehydration, active and passive pyrolysis. Two-steps degradation of raw olive stone occurred, whereas the impregnated material displayed only one step. Addition of phosphoric acid sharply reduced the onset temperature of the main decomposition step. Onset temperatures decreased with increasing rate or time of impregnation. It could conclude that 3 h is sufficient as time of impregnation for activated carbon production. Examination of the main gas products were carried out using coupled TGA-MS. The principal permanent gases detected were H$_{2}$, H$_{2}$O, CO, CO$_{2}$ and the light hydrocarbons C$_{2}$H$_{6}$ and CH$_{4}$. Different kinetic scenarios of raw and impregnated olive stones were observed. The above results should be useful to understand the pyrolysis mechanism of phosphoric acid impregnated olive stone for improving activated carbon production

Hydrogen production by methane decomposition over Ni-doped activated carbons: effect of the activation method

Ni supported over activated carbon (AC) based on olive stones were tested for methane decomposition to produce hydrogen. Physical (by $\mathrm{H}_{2}\mathrm{O}$) and chemical (by $\mathrm{H}_{3}\mathrm{PO}_{4}$) activations were compared. Kinetic parameters of methane decomposition were determined depending on Ni load, methane partial pressure and reaction temperature. The catalysts were characterized before and after reaction by $\mathrm{N}_{2}$ adsorption, X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The catalysts showed good initial activities that increased with temperature and nickel load, reactivity decreased with time. The reaction orders were 0.63 and 0.74 and the activation energies were 122 and 139 kJ/mol for physically and chemically activated carbon, respectively. BET surface areas and pore volumes decreased dramatically after reaction due to the deposit of carbon on the support. Ni stayed under its metallic form on the physically AC whereas it was mainly present as $\mathrm{Ni}_{12}\mathrm{P}_{5}$ over the chemically activated one. TEM characterization revealed the formation of well-organized carbon nano-onions surrounding Ni particles on the physically activated carbon. Nano-onions were not formed around $\mathrm{Ni}_{12}\mathrm{P}_{5}$ particles in the chemically activated carbon. The physical activation allowed the synthesis of catalysts with a better stability for methane conversion than what chemical activation would allow

Optimization of CO2 Capture Efficiency in a Flue Gas Treatment System: Assessing the Impact of Flow Rates, Absorbent Concentrations, Nanoparticles, and Temperature

This study focuses on improving the efficiency of flue gas purification systems for carbon dioxide (CO2) capture. The researchers investigated various factors, including flow rates, absorbent concentrations, nanoparticles, and temperature, to optimize the CO2 capture process. They conducted experiments using a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor to separate CO2 from nitrogen. The presence of titanium dioxide and silica nanoparticles in a potassium carbonate solution facilitated the separation process. The findings indicate that optimizing flow rates and absorbent concentrations can enhance CO2 capture efficiency. The use of nanoparticles in the absorbent solution was found to improve material capture effectiveness. The study also revealed that higher temperatures contribute to increased CO2 capture efficiency. The research aims to advance CO2 capture techniques to mitigate the release of industrial greenhouse gases, particularly in flue gas treatment systems. The researchers determined optimal settings for CO2 capture in these systems, emphasizing the importance of absorbent concentration for stability and absorption, as well as the role of nanoparticles in enhancing reaction kinetics and CO2 collection. The objective of the analysis is to maximize removal efficiency, although specific lower and upper bounds and a target value were not provided. The proposed solution suggests specific values for the independent variables, including temperature, gas flow rate, liquid flow rate, and the concentrations of K2CO3, PZ, SiO2, and TiO2, to optimize CO2 capture

APPLICATION OF ACTIVATED CARBON PREPARED FROM OLIVE STONES IN THE REMOVAL OF TWO BASIC DYES FROM WATER

Olive stones is produced in large quantities during the manufacture process of the olive oil in the Tunisian oleic industry. This by-product. have been converted to granular activated carbon by carbonisation in the nitrogen atmosphere followed by steam activation. Activated carbon so obtained with 1150 m2/g specific surface area and 0,53 cm3/g pore volume, essentially microporous, has been used for the adsorption of two basic dyes: Methylene Blue (MB) and Rhodamine B (RB) in aqueous solution. The equilibrium adsorption isotherms of the two dyes at 30°C shows Langmuir shape. The maximum adsorption capacity of MB and RB are found to be 303 mg/g and 217 mg/g respectively. Adsorbent affinity to tested dyes is related to electric and steric effects. KEY WORDS: Olive stones, activated carbon, Methylene Blue, Rhodamine B, adsorption Global Jnl Pure & Applied Sciences Vol.10(1) 2004: 91-9