Removal of Color and Organic Matter in Industrial Phosphoric Acid by Ozone: Effect on Activated Carbon Treatment

Industrial phosphoric acid at 42-45% P₂O₅ and containing organic matter (OM) in the range of 220 mg/L to 300 mg/L is treated by combined ozonation and activated carbon. Ozonation alone removes the initial dark color of the acid and eliminates the organic content. Adsorption on activated carbon alone can reduce OM levels by 80% for more than 25 g/kg P₂O₅. We find that a preozonation noticeably enhances activated carbon efficiency and reduces its specific consumption. Isoconversion curves are plotted in specific ozone and activated carbon ratio space.     

Ozone Decomposition over Cobalt Supported on Olive Stones Activated Carbon: Effect of Preparation Method on Catalyst Activity

Aqueous ozone decomposition was studied over highly dispersed cobalt nanoparticles supported on olive stones activated carbon (AC) prepared by: wetness impregnation (Co/AC_w) and incipient wetness impregnation (Co/AC_iw) with respect to pore volume. Nitrogen adsorption-desorption at 77K, SEM, XRD and XPS analyses were used to characterize the catalysts. Analyses results show that Co/AC_w was more uniformly dispersed on the AC than Co/AC_iw. The effect of the presence of tert-butanol as radical scavenger was also studied. Higher catalytic activity was measured for Co/AC_w than Co/AC_iw. Ozone decomposition extent goes to 99% in only 3 min in the presence of Co/AC_w compared to 60% and 58% using Co/AC_iw catalyst and AC, respectively.     

Olive stones based carbon foam: synthesis,characterization and application on post-combustion CO2 adsorption

Journal of Porous Materials - In the present paper, the performance of carbon foams to adsorb CO2 in post-combustion conditions using a thermo-gravimetric analyzer was investigated. Two types of...     

An Optimization Study of Cobalt Supported on Activated Carbon for the Catalytic Ozonation of Oxalic Acid: Effect of Operating Parameters and Synergetic Combination

In this study, new heterogeneous cobalt (Co) catalysts supported on activated carbon (Co/AC) were developed using a wetness impregnation process. The effect of preparation conditions on catalyst characteristics was examined. This work focused on two key parameters: the impregnation rate and the calcination atmosphere (temperature and time). Different catalysts were prepared by varying the Co loading on AC. Various catalysts were characterized by means of nitrogen sorptiometry at 77K, Boehm and pHpzc analysis. It was found that the catalyst properties and the functional surface groups were affected by the operating conditions. The best surface area was 997.5 m2/g obtained when the activated carbon was impregnated with 5% Co loading and calcined at 350°C for 2 h. The effects of parameters, such as cobalt loading, pH, catalyst dose, and ozone dose, were explored on oxalic acid removal (OA). Results show that the use of Co/AC for heterogeneous catalytic ozonation enhanced the degradation efficiency of oxalic acid (OA) significantly compared with simple ozonation and O3/AC. The main results indicate that the optimum catalytic activity was observed when 5% (wt/wt) of Co was supported on AC reaching a catalytic ozonation efficiency of 95%. The results of total organic carbon removal of 91% were achieved at optimum conditions.     

Ozone Absorption in Water: Mass Transfer and Solubility

Mass Transfer of ozone absorbed by water in a semi-comtinuous stirred reactor is studied at the lab scale. Experimental investigation using a complete factorial scheme shows a predominant effect of agitation speed and gas flow and results in a correlation for the mass transfer coefficient, k₁a. Solubility of ozone in water is estimated by evaluation of an apparent Henry's law constant for different temperatures (20* and 50*C), pH values (2 and 7) and a t constant ionic strength (0.13).     

硝酸浓度对橄榄石基活性炭特性的影响(英文)

In this work we investigated the effect of nitric acid concentration on the pore structure, surface chemistry and liquid phase adsorption of olive stone based activated carbon prepared by mixing process using phosphoric acid and steam as activating agents. Chemicals and textural characterization show that the increase of HNO3 concentration increases considerably the total acidic groups but decreases specific surface area and pore volume. The study of adsorption in aqueous solutions of two organics, phenol and methylene blue, on raw and oxidized activated carbon indicates that the treatment of mixed activated carbon with different concentrations of nitric acid improves the adsorbent capacity for methylene blue at HNO3 concentrations less or equal to 2 mol·L 1, while it has a negative effect on phenol adsorption.     

Evaluation of activated carbons based on olive stones as catalysts during hydrogen production by thermocatalytic decomposition of methane

Catalytic decomposition of methane over carbon materials has been intensively studied as an environmental approach for CO₂-free hydrogen production without further by-products except hydrogen and valuable carbon. In this work, we will investigate the catalytic activity of activated carbons based on olive stones prepared by two different processes. Additionally, the effect of three major operational parameters: temperature, weight of catalyst and flow rate of methane, was determined. Therefore, a series of experiments were conducted in a horizontal-flow fixed bed reactor. The outflow gases were analysed using a mass spectrometer. The textural, structural and surface chemistry properties of both fresh and used activated carbons were determined respectively by N₂ gas adsorption, X-Ray Diffraction and Raman and Temperature Programmed Desorption. The results reveal that methane decomposition rate increases with temperature and methane flow however it decreases with catalyst weight. The two carbon samples exhibit a high initial activity followed by a rapid decay. Textural characterization of the deactivated carbon presents a dramatic drop of surface area, pore and micropore volumes against an increase of average pore diameter confirming that methane decomposition occurs mainly in micropores. XRD characterization shows a turbostratic structure of fresh samples with more graphitization in deposed carbon explaining the lowest activity at the end of reaction. Raman spectra reveal the domination of the two bands G and D which varying intensities affirm that the different carbons tend to organise in aromatic rings. Finally the surface chemistry qualitatively changes greatly after methane dissociation for CAGOC unlike CAGOP but quantitatively a small difference is observed which indicates that these functionalities may have a role in this heterogeneous reaction but cannot be totally responsible. Among the two catalysts tested, CAGOC has the highest initial methane decomposition rate but CAGOP is the most stable one.     

A correct-by-construction model for asynchronously communicating systems

International Journal on Software Tools for Technology Transfer - The design and verification of distributed software systems is often hindered by their ever-increasing complexity and their...     

Ozone decomposition on glass and silica

Ozone decomposition on glass and silica surfaces is studied by means of non‐porous particles in a fixed bed (sand, glass bead, crushed glass bead, silica). Influences of gas velocity, particle diameter and reactor volume are investigated. Ozone is produced by a silent discharge generator. A model considering the geometric characteristics of material is used so that the ozone decomposition rate per unit of surface area is identified. The decomposition reaction is represented by means of an apparent first‐order kinetic constant. The high dependency of the apparent kinetic constant on the surface area, for given flow rates, suggests that the ozone decomposition mechanism is not simple. Due to the values of the apparent first order kinetic constant, the existence of catalytic species produced by the ozone generator, as well as excited ozone and/or oxygen species, are considered, by means of several models, to explain the experimental results.