Quantum chemical approach (DFT) of the binary complexation of Hg(II) with L-canavanine and L-arginine.

The experimental study of the complexation of the two amino acids, L-canavanine, and L-arginine, with the mercuric ion Hg(II), was completed by the characterization by a quantum calculation based on the DFT method. This study covers electronic, energetic, and structural aspects in the neutral, deprotonated, and complexed states. The atomic net charges show that the active sites of the carboxyl, guanidyl, and amino groups are the oxygen and nitrogen atoms. In fact, the L-canavanine (Can) gave stable mercuric bidentate chelates via the amino and guanidyl groups. Hg(Can)(H2O)2, Hg(Can)2 and Hg(OH)(H2O)(Can), while the L-arginine (Arg) resulted in engagement of carboxyl and amino groups to bidentate complexes: Hg(Arg)(H2O)2, Hg(Arg)2, Hg(Arg)(OH)(H2O). The metal-ligand coordination bond is more rigid with the guanidyl and carboxyl groups than with the amino group; and the bond formed with the amino group is more rigid in the L-canavanine than L-arginine

Mild steel corrosion inhibition by some heteroatom organic compounds in acetic acid medium

Four heteroatom organic compounds (HAC) such as L-methionine (Meth), L-Cysteine (Syst), Phenyl MercaptoTetrazol (PMT) and Glutamic acid (GA) were evaluated as corrosion inhibitors for mild steel in 1M acetic acid (AcA) solution. The technique used are potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), UV-Vis spectroscopy analysisand scanning electron microscopy (SEM). As a comparative study results, the corrosion inhibitor rankings were: Meth ˂ Cyst ˂ PMT ˂ GA. Furthermore, the GA was the best inhibitors against mild steel corrosion and provided an inhibition efficiency of 74% at 10-4M. For this reason, we have besides studied the GA concentration and immersion time on the performance delivered by GA. In this way, it is affirmed that the inhibition efficiency was well improved with the GA concentration increasing. In addition, the GA is a good corrosion inhibitor even with long durations.

Application of Castor plant (Ricinus communis. L) as a green sorbent for removing cationic dyes from textile effluents.

The present study reports the removal of cationic dyes from water using Castor plant byproducts (castor seed shell (CC), castor seed shell envelope (CE), and castor leaves (CF)) as low-cost and ecofriendly materials. The different parts of the castor plant were characterized using various techniques such as FTIR, X-Ray diffraction, SEM and EDX analysis. Dye adsorption experiments were conducted in a batch reactor to study the kinetics, thermodynamics, and equilibrium of the adsorption process. The adsorption was strongly described by Langmuir isotherm, and followed the pseudo second-order-kinetic model. The thermodynamic parameters indicate that the adsorption in this case is an exothermic, spontaneous and physical process. The results showed that all the castor plant materials had a much higher uptake capacity for the Toluidine Blue (TB) dye compared to Yellow X-GL 200% (YX-GL) one, reaching maximum adsorption capacities above 1107.69 mg.g-1 for BT and 109.02 mg.g-1 for YX-GL. The desorption study showed that different Castor plant based-adsorbents could be reused multiple times (at last 6 times) without losing their adsorption performance. Overall, the experimental outcomes demonstrated that the Castor plant byproducts may be considered as efficient and reusable alternative adsorbents for the treatment of dye-contaminated effluents

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives

Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2−. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field

Effect of the temperature on the synthesis of dicalcium phosphate dihydrate

The use of calcium phosphates as biomaterials was largely developed during the last decades. Among the phosphorous compounds solid minerals of biological interest, the dicalcium phosphate dihydrate, (DCPD or brushite) (CaHPO$_{4}$, 2H$_{2}$O), disserves a special attention. It can be prepared in different ways. The manufacture of inorganic phosphate, it is usually produced by the acidulation of limestone form of calcium with phosphoric acid. The synthesis of this phosphate depends on many operational parameters. This study was performed in order to verify the influence of temperature and the time on the chemical purity and the yield of precipitation. All the samples were characterized by X-ray diffraction, infrared spectrometry and chemical analysis

Single and multi-component adsorption of aromatic acids using an eco-friendly polyaniline-based biocomposite

The polyaniline coated with an agricultural waste (Argan nut shell) was prepared via in-situ chemical polymerization and used as an adsorbent material for removal of trimellitic (Tri), hemimellitic (Hemi) and pyromellitic (Pyro) acids from water in single and multi-component systems. The obtained results indicate that the adsorption process was strongly influenced by experimental parameters. The greatest adsorption efficiency was obtained at pH 6, adsorbent dose = 0.5 g/L, T = 25 °C, contact time = 90 min and initial concentration of 20 mg/L. The experimental data for single component systems fitted very well to pseudo-second-order kinetic model (R2 = 0.999). The intraparticle diffusion model suggests that the adsorption of Tri, Hemi and Pyro acids takes place in two successive stages representing the progressive adsorption and equilibrium. The single component adsorption equilibrium data were successfully described by the Langmuir isotherm model (R2 ≥ 0.995). The maximum monolayer adsorption capacity of polyaniline/Argan-nut-shell composite was found to be 209.64, 143.68 and 267.38 mg/g for Tri, Hemi and Pyro acids, respectively. In binary and ternary systems, the competitive behavior of the adsorption process was successfully predicted by an extended Langmuir isotherm model, with interaction parameters obtained from measured single data. Furthermore, the values of thermodynamic parameters (ΔH° ˃ 0, ΔS° ˃ 0 and ΔG ˂ 0) indicate that the adsorption processes were spontaneous, endothermic and physisorption in nature.Scopu