Mg and La Co-doped ZnO Nanoparticles Prepared by Sol–gel Method: Synthesis, Characterization and Photocatalytic Activity

In this study, La and Mg doped, and co-doped ZnO nanoparticles were prepared using the sol-gel method. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and N2 physisorption techniques. The XRD results indicated that the prepared nanoparticles can be well adopted by the hexagonal wurtzite structure crystal and there are no second impurity peaks. Studies of the FESEM, EDX and TEM have shown that the samples have uniform spherical-like morphology with a homogenous distribution. The incorporation of La and Mg into the ZnO lattice had no effect on the morphology of the nanoparticles, but a reduction in the size of the grains (≈ 14 nm to ≈ 7 nm) was observed due to the insertion of these ions. The results of N2 physisorption indicated that there was an increase in BET surface area and pore volume for doped and co-doped samples. The results of DRS showed an increase in band gap energy and a blue shift at the absorption edge for doped and co-doped samples. The photocatalytic activity of the prepared catalysts was evaluated in the removal of RhB under UVA irradiation. The results showed that Mg5%-La5%/ZnO had the highest photoactivity (91.18 %) among all samples

Intensification of Azo Dye Removal Rate in the Presence of Immobilized Nanoparticles and Inorganic Anions under UV-C Irradiation: Optimization by Response Surface Methodology

Wastewaters contain inorganic anions that affect the removal rate of organic pollutants. The present study aims to optimize the effects of inorganic anions such as , Cl−, , and on the removal rate of an organic pollutant in the presence of immobilized TiO2 nanoparticles using response surface methodology (RSM). C.I. Acid Red 17 (AR17) was used as a model organic pollutant. Thirty experiments were required to study the effects of anions in various concentrations. The results indicate that the addition of and ions intensifies the removal rate of AR17. The results of the analysis of variance (ANOVA) showed a high coefficient of determination value ( and ). The results indicate that RSM is a suitable method for modeling and optimizing the process. The results prove that in the presence of and and ions especially in the combination situation the removal rate of AR17 is enhanced considerably. An important synergy effect was observed in the combination of and ions, so that AR17 removal percent under the optimized RSM conditions was considerably more than the sum of removal percent when these ions are used individually

INFLUENCE OF THE CHEMICAL STRUCTURE OF ORGANIC POLLUTANTS ON PHOTOCATALYTIC ACTIVITY OF TiO 2 NANOPARTICLES: KINETIC ANALYSIS AND EVALUATION OF ELECTRICAL ENERGY PER ORDER (E EO )

Photocatalytic degradation of different organic pollutants such as C.I. Acid Red 27(AR27), Methyl Orange (MO), Malachite Green (MG) and 4-Nitrophenol (4-NP) were investigated under UV light irradiation using synthesized TiO 2 nanoparticles by sol-gel method. It was found that the photocatalytic degradation rate depends on pollutants structure. The results indicate that from these pollutants MG can be removed faster than other pollutants. Also, 4-NP with a more stable structure than other pollutants has lowest removal rate in the presence of TiO 2 nanoparticles under UV light irradiation. The results prove that removal rate of pollutants with different structures follows pseudo-first order kinetics. The figures-of-merit based on electric energy consumption (electrical energy per order (E EO )) were evaluated in the photocatalytic degradation of four organic pollutants. The results indicate that E EO values depend on the basic structure of the pollutants

Determination of the Optimum Conditions for the Leaching of Lead from Zinc Plant Residues in NaCl–H₂SO₄–Ca(OH)₂ Media by the Taguchi Method

This research is part of a continuing effort to reduce environmental conflicts and occupational hazards of lead-bearing zinc plant residues (ZPRs), and to break through this problem and recover lead of the wastes. The residue with an assay of 14.4% Pb was used in chloride leaching for lead recovery, and sulfate was controlled in the leaching stage by the addition of Ca­(OH)₂. In this paper, the effects of influential factors on extraction efficiency of Pb from ZPRs were investigated. Taguchi’s method based on orthogonal array design (OAD) has been used to arrange the experimental runs in order to maximize lead extraction from a ZPR. Orthogonal array (OA) L₈(2⁷) consisting of seven parameters, each with two levels, was employed to evaluate the effects of NaCl concentration (<i>C</i> = 300 and 400 g/L), stirring speed (<i>R</i> = 500 and 700 rpm), reaction temperature (<i>T</i> = 55 and 65 ◦C), reaction time (<i>t</i> = 1 and 8 h), liquid-to-solid ratio (L/S = 6 and 20), acidic pH (pH_a= 2 and 3.5), and neutral pH (pH_b= 4 and 5.5) on lead extraction percent. Statistical analysis, ANOVA, was also employed to determine the relationship between experimental conditions and yield levels. The results showed that the pulp density, and NaCl concentration were significant parameters, and increasing pulp density reduced leaching efficiency of lead. However, increasing NaCl concentration promoted the extraction of lead. The obtained optimum conditions from this study were <i>C</i>₂, 400 g/L; <i>R</i>₂, 700 rpm; <i>T</i>₁, 55 °C; <i>t</i>₁, 1 h; (L/S)₂, 20; (pH_a)₂, 3.5; and (pH_b)₁, 4. But only two significant factors (<i>C</i>₂, 400 g/L; and (L/S)₂, 20) were used to estimate the performance at the optimum conditions. The calculated leaching percent (85.91%) was in reasonable agreement with the experimental results in optimum conditions

Study of the Effect of Additives on the Photocatalytic Degradation of a Triphenylmethane Dye in the Presence of Immobilized TiO₂/NiO Nanoparticles: Artificial Neural Network Modeling

In the present work, TiO₂/NiO coupled nanoparticles were prepared from a powder mixture of the corresponding component solid oxides by using an impregnation technique. Then, the prepared TiO₂/NiO nanoparticles were immobilized on glass plate and used as a fixed-bed photocatalytic system for photodegradation of Acid Fuchsin (AF), as a triphenylmethane dye pollutant. The effects of nature and concentration of various additives included inorganic oxidants (such as HSO₅^–, IO₄^–, ClO₃^–, S₂O₈^2–, H₂O₂, and BrO₃^–), inorganic anions (such as CH₃COO^–, CO₃^2–, NO₃^–, Cl^–, H₂PO₄^–, and SO₄^2–), and transition-metal ions (such as Co²⁺, Zn²⁺, Fe²⁺, Cu²⁺, Ni²⁺, and Mn²⁺) on photocatalytic degradation of AF, were investigated. It was found that the nature and concentration of studied additives significantly affected the photocatalytic degradation of dye pollutant in fixed-bed systems. The transition-metal ions and inorganic oxidants have a positive effect on the photocatalytic degradation rate of AF dye, whereas inorganic anions have a negative effect. An artificial neural network (ANN) model was designed for modeling of the photocatalytic degradation rate of AF dye. The results showed that the predicted data from designed ANN model were in good agreement with the experimental data. Designed ANN provides a reliable method for modeling the photocatalytic activity of immobilized TiO₂/NiO nanoparticles in the presence of various additives