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Methylene blue dye (MB), prevalent in textiles like cotton, wood, and silk, raises environmental and health concerns. This study presents a successful synthesis of a Bayerite/zeolite nanocomposite powder using fumed silica by-product and aluminum nitrate. Hydrothermal exploration of factors, including duration, temperature, and Al/Si ratios, revealed that high temperature (160°C) and short duration (6h) favored optimal crystallization of bayerite/zeolite phases. Subsequently, an integrated photocatalytic adsorbent (IPA) was developed by mechanically mixing the synthesized bayerite/zeolite with TiO2, followed by calcination (500 °C, 2 h), demonstrating superior efficiency in MB photodegradation under UV–Vis light. The IPA achieved 100% degradation efficiency for 60 mg/L of MB and maintained good photostability over three cycles. The bayerite/zeolite-supported TiO2 nanocomposite exhibited the generation of positive holes (h +) and active hydroxyl radicals (OH•), showcasing its potential as a promising material for wastewater treatment applications. Highlights: • Successful synthesis of Bayerite/zeolite nanocomposite powder from fumed silica waste and aluminum nitrate. • Development of an integrated photocatalytic adsorbent (IPA) by mixing synthesized bayerite/zeolite with TiO2. • IPA demonstrated superior efficiency in Methylene Blue (MB) photodegradation under UV-Vis light • The bayerite/zeolite-supported TiO2 nanocomposite maintained good photostability over three cycles, showcasing its potential for wastewater treatment applications. [ABSTRACT FROM AUTHOR]

Arsenopyrite (FeAsS) stands as one of the primary host minerals for refractory gold, where the gold is finely disseminated or chemically locked up within the matrix of these raw materials. Therefore, oxidation of this sulfide mineral is necessary for the liberation of gold (Au), and then improving its extraction. This paper aims to study the chemical oxidation of arsenopyrite by four oxidizing agents: S2O82-, H2O2, ClO4- and Cr2O72-. The objective was to enhance the oxidation efficiency of arsenopyrite through examining the impact of pH, acid type, and reaction time. The findings showed that S2O82- is the most effective oxidant for arsenopyrite, and the oxidation efficiency varies in the following order: S2O82- > H2O2 > ClO4- > Cr2O72-. The optimum pH for all the studied oxidizing agent was pH=2. The effect of acid type experiments revealed that, for each oxidant, HClO4 was the optimum acid to be used in regulating pH, and the effect of acid type varies in the following order: HClO4 > HNO3 > HCl > H2SO4. The highest oxidation rate recorded in this study was in the case of S2O82- oxidizing agent with pH regulated by HClO4, for which the oxidation efficiency achieved 81.90 % for As oxidation, and 63.94 % for Fe oxidation. This study will help to develop an oxidative pretreatment processes for refractory arsenopyritic gold ores. [ABSTRACT FROM AUTHOR]

This work deals with the study of the inhibition activity of three thiazolidinones (prepared from monoterpenic ketones) on the deterioration of S300 steel in hydrochloric acid solution. The potentiodynamic polarization was used to investigate the electrochemical behavior of the studied inhibitors which were revealed to be mixed type ones. It was established that the studied compounds have significantly inhibited the dissolution of steel with the highest inhibition efficiency of 84% at 293 K. This inhibition efficiency increases with an increase in the inhibitor's concentrations ranging between 1 × 10−4 and 5 × 10−3mol/L, proving the mixed type character. Moreover, the corrosion behavior of steel in 1 M HCl in the absence and presence of the inhibitors at 5 × 10−3mol/L was studied at the temperature range of 293 − 323 K. The obtained results also revealed that the adsorption of inhibitors on steel surface might take place at specific homogeneous sites, obeying to the Langmuir adsorption isotherm. Thermodynamic parameters such as enthalpy, entropy and activation energy were determined. The scanning electron microscopy combined with dispersive X-ray spectroscopy examinations and Raman technique was used to explore the surface morphology and the elemental composition. Scanning electron microscope (SEM) images show that the surface damage is reduced in the presence of the three studied inhibitors. The quantum chemical calculations using density functional theory (DFT) were performed to provide some insights into the electronic density distribution as well as the nature of inhibitor-steel interaction. The corresponding results show that the three thiazolidinones act as inhibitors by improving a good barrier for corrosion protection. Also, the rearrangement in the compound's structure affects their inhibitory activity. [ABSTRACT FROM AUTHOR]

In the present study, the effects of aging and formation potential on the semiconducting behavior of AISI 321 stainless steel as well as the kinetics of the early stages of pitting are discussed. The donor and acceptor densities decrease with increasing formation potential. The steady-state passive film thickness and the coefficient of oxygen vacancies are estimated. The electrode polarization at higher anodic potentials causes the increase in the rate of pit initiation and slows down the growth rate of passive film. Also, the openness of the pits and their coalescence are highly promoted with the increase in the applied potential. [ABSTRACT FROM AUTHOR]

In Morocco, many regions suffer from water scarcity. In order to address the arid zone water shortage in the Marrakech region, the reuse of wastewaters in agriculture can present new alternatives. However, there are significant concerns about the safety of wastewater reuse especially for irrigation purposes that can be insured by reducing the wastewater pollutants amount by accessible and inexpensive processes like slow sand filtration (SSF). In order to study the removal efficiency of SSF, a continuous fixed-bed adsorption study was achieved by using sand as an adsorbent of metallic trace elements (Cd, Cu, Pb and Zn) from contaminated water of Tensift River. This river received wastewater directly from industrial unit of Zn and Pb extraction of Draa Lasfar mine located at 13 km in north-west of Marrakech City in Morocco. Results showed that SSF can remove 100% of metallic pollutants and the removal efficiency of this process to decontaminate water depends greatly on the sand bed height (filter). Thus, the long filter eliminates more pollutants than the smaller ones. This result can be attributed to the exposition of new fixation sites of metallic pollutants on the sand surface that facilitates their adsorption process. The dynamic behavior of adsorption mechanism used in SSF process is predicted by using Langmuir kinetics of adsorption-desorption with no axial dispersion. [ABSTRACT FROM AUTHOR]

In this study, the potential use of a novel electrode composed of palygorskite, a natural nanomaterial with a hollow structure, for the detection of Cd2+was investigated. Moreover, the electrode’s efficiency under various operating conditions was assessed through response surface methodology. For this purpose, cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy were utilized along with Doehlert experimental design methodology. The findings demonstrated that the electrode’s sensitivity was enhanced by using HCl solution (10−2 M) as a supporting electrolyte or by increasing Cd2⁺ ion concentration. Additionally, the weights of the effects of the factors on electrode sensitivity followed the order Cd2⁺ concentration > pH > scan rate. The estimated limit of detection was approximately 2.03 × 10−4 mol/L; however, experimentally, Cd2+ concentrations as low as 5 × 10−5 M could be detected. The electrode exhibited selectivity in detecting Cd2⁺ and Pb2⁺ ions in arable land. Furthermore, it could be regenerated through a mild chemical treatment involving cation exchange. On the other hand, the electrode/solution interface could be likened to an electric circuit comprising solution resistance (162 Ω.cm2), charge transfer resistance (19.850 Ω.cm2), double-layer capacitor (11.3 × 10−6 Fs(α-1)), and Warburg diffusion element (150 s−1). These data as well as the electrode’s performance were mainly discussed in the sight of the physical and structural characteristics of palygorskite.Graphical Abstract: In this study, the potential use of a novel electrode composed of palygorskite, a natural nanomaterial with a hollow structure, for the detection of Cd2+was investigated. Moreover, the electrode’s efficiency under various operating conditions was assessed through response surface methodology. For this purpose, cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy were utilized along with Doehlert experimental design methodology. The findings demonstrated that the electrode’s sensitivity was enhanced by using HCl solution (10−2 M) as a supporting electrolyte or by increasing Cd2⁺ ion concentration. Additionally, the weights of the effects of the factors on electrode sensitivity followed the order Cd2⁺ concentration > pH > scan rate. The estimated limit of detection was approximately 2.03 × 10−4 mol/L; however, experimentally, Cd2+ concentrations as low as 5 × 10−5 M could be detected. The electrode exhibited selectivity in detecting Cd2⁺ and Pb2⁺ ions in arable land. Furthermore, it could be regenerated through a mild chemical treatment involving cation exchange. On the other hand, the electrode/solution interface could be likened to an electric circuit comprising solution resistance (162 Ω.cm2), charge transfer resistance (19.850 Ω.cm2), double-layer capacitor (11.3 × 10−6 Fs(α-1)), and Warburg diffusion element (150 s−1). These data as well as the electrode’s performance were mainly discussed in the sight of the physical and structural characteristics of palygorskite. [ABSTRACT FROM AUTHOR]