The occurrence of chlorinated pesticides in wellwaters is a major problem of public health in Ivory Coast and other African countries. Here, we studied the photocatalytic degradation of the pesticide diuron in aqueous solution in presence of two commercial TiO 2 catalysts, P25 and PC500. The capacity of diuron adsorption at the TiO 2 surface is lower for both photocatalysts. The efficiency of photocatalytic degradation of diuron, it is higher using P25 Degussa than PC500 Millenium TiO 2 catalyst.
In this work, low cost coconut biochar based activated carbon (CBAC) was used for adsorption of Butylparaben (BPB) from aqueous medium. The prepared CBAC was characterized using BET, Boehm analysis and the adsorption equilibrium, kinetics and thermodynamics studies of BPB adsorption were carried out. During batch adsorption runs, the effects of factors, such as contact time (0 -300 min), CBAC dose (200 -800 mg), pH (3 -11) and solution temperatures (303 -348 K) were investigated on BPB removal. Experimental results reveal that the BPB removal efficiency on CBAC is higher than 97% under acidic and neutral conditions. Equilibrium data were fitted by Langmuir, Freundlich and Temkin isotherm models with correlation coefficient more than 0.9. The pseudo-second order kinetic model was observed to fit well the adsorption data. Thermodynamic analysis shows positive values of standard Gibb's free energy, suggesting the non-spontaneity of the process. The changes in enthalpy (0.2 J·mol −1 ) and entropy (19 J·mol −1 ) were found to be endothermic with an increase of randomness. The high adsorption efficiency of the synthesized coconut biochar materials with low cost indicates that it may be a promising adsorbent for removing organic compounds.
The objective of this work is to prepare one of the best activated carbon (CA) based on wood (Acacia auriculeaformis). The chemical activation method was used for varying the chemical agent namely phosphoric acid H 3 PO 4 (CAA), sodium hydroxide NaOH (CAB), and sodium chloride NaCl (CAS). The physico-chemical analysis of the three activated carbons indicated that, under the conditions of preparation, the activated carbons possess activation efficiencies lower than 50% (41.81% for CAA, 26.25% for CAB and 48.87% for CAS), low ash content (CAA: 5.00%, CAB: 14.90 and CAS: 6.60%) and iodine values ranging from 190.35 mg/g to 380.71 mg/g, suggesting that the good quality of the prepared activated carbon. The surface functional groups using Boehm test and the zero point charge (pH ZPC) methods confirmed the acidic, basic and neutral character for CAA, CAB and CAS respectively (CAA: pH ZPC = 4.8, CAB: pH ZPC = 8.2, CAS: pH ZPC = 6.8). The surface specific areas were determined through the liquid phase adsorption of acetic acid and methylene blue using the Langmuir method and BET analysis. Also, the porosity was determined. The BET surface areas of CAA, CAB and CAS were respectively 561.60 m 2 /g, 265.00 m 2 /g and 395.40 m 2 /g. The influence of chemical activation agent on pores formation was confirmed by scanning electron microscopic (SEM) analysis. CAA was selected as the best activated carbon because of its good surface area and good pore volume compared to those found in the literature. Therefore, its application as an adsorbent for effluents treatment could be explored. In addition, the best activating agent for coal from Acacia auriculeaformis was found to be phosphoric acid.
Herein, we report the synthesis of N-tert-butoxycarbonyl (BOC) protected [V 6 O 13 {(OCH 2) 3 C-NH 2 } 2 ] 2built from the Lindqvist-type hexavanadate. The reaction of di-tert-butyl dicarbonate (BOC 2 O) with tris(hydroxymethyl)aminomethane (Tris) led to the organic derivative [(OCH 2) 3 C-NH(BOC)] that reacts with the decavanadate in dimethylacetamide (DMA) to form the [V 6 O 13 {(OCH 2) 3 C-NH(BOC)} 2 ] 2anions. The tetrabutylammonium (TBA +) salt of this hybrid polyoxovanadate, TBA 2 [V 6 O 13 {(OCH 2) 3 C-NH(BOC)} 2 ]•2DMA, has been characterized in the solid-state by single crystal X-ray diffraction and infrared spectroscopy, and in solution by multinuclear (1 H, 13 C and 51 V) and DOSY NMR, and UV-visible spectroscopy.
The present work evaluates the potential of the photocatalysis (PC) process for the degradation of butylparaben (BPB). Relatively high treatment efficiency was achieved by comparison to photochemical process. Prior to photocatalytic degradation, adsorption (AD) of BPB occurred on the titanium dioxide (TiO2)-supported catalyst. AD was described by Langmuir isotherm (KL = 0.085 L g(-1), qm = 4.77 mg g(-1)). The influence of angle of inclination of the reactor, pH, recirculation flow rate and initial concentration of BPB were investigated. The PC process applied under optimal operating conditions (recirculation flow rate of 0.15 L min(-1), angle of inclination of 15°, pH = 7 and 5 mg L(-1) of BPB) is able to oxidize 84.9-96.6% of BPB and to ensure around 38.7% of mineralization. The Langmuir-Hinshelwood kinetic model described well the photocatalytic oxidation of BPB (k = 7.02 mg L(-1) h(-1), K = 0.364 L mg(-1)).
In order to remove pesticides from water, a basic photoreactor has been built. We evaluated the performance of this photoreactor using two commercial photocatalytic materials from Ahlstrom group and from Saint-Gobain, with solar and artificial UV-lamps. We compared the kinetics of photocatalytic degradation and mineralization of Diuron in the same reactor with of both photocatalyst supports. We showed that Diuron is easily degraded under solar or artificial irradiation, while the kinetics of mineralization in the same condition are very slow. The behaviour of these commercial materials has been studied after several uses in the same conditions. We showed the effectiveness of this basic and cheap photoreactor for the elimination of pesticide in water.
Iodization of dietary salt is recommended to prevent and control iodine deficiency disorders. The kinetic study of dietary iodized salt proves to be of interest not only for the determination of the conditions of production of iodine, but also for a good knowledge of the kinetic and thermodynamic parameters of the reaction. In this work, two salt brands were studied and one of them was used for the kinetic study. The kinetic study showed that the reaction proceeded slowly at a medium rate. Since the reaction admits a global order equal to 1, potassium iodide has no influence on this reaction rate. The concentration of iodate ions introduced in the dietary salt is a kinetic parameter that affects the reaction rate. Calculated rate constant was inversely proportional to time. The study has therefore determined experimentally kinetic parameters of the reaction between iodate and iodide ions.
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