Influence Of Solution Acidity Research Articles

Assessment of chromite ore wastes for methylene blue adsorption: Isotherm, kinetic, thermodynamic studies, ANN, and statistical physics modeling

This research investigates the adsorption potential of chrysotile and lizardite, two minerals derived from chromite ore wastes, for the uptake of Methylene Blue (MB) dye from waste streams. The characterization of these minerals involves XRD, XRF, FTIR, and SEM. Results confirm the dominance of polymorphic magnesium silicate minerals, specifically chrysotile and lizardite, in the samples. The FTIR spectra reveal characteristic vibration bands confirming the presence of these minerals. The SEM analysis depicts irregular surfaces with broken and bent edges, suggesting favorable morphologies for adsorption. N2 adsorption-desorption isotherms indicate mesoporous structures with Type IV pores in both adsorbents. The Central Composite Design approach is employed to optimize MB adsorption conditions, revealing the significance of contact time, adsorbent mass, and initial MB concentration. The proposed models exhibit high significance, with F-values and low p-values indicating the importance of the studied factors. Experimental validation confirms the accuracy of the models, and the optimum conditions for MB adsorption are determined. The influence of solution acidity on MB uptake is investigated, showing a significant enhancement at higher pH values. Isothermal studies indicate Langmuir and Freundlich models as suitable descriptions for MB adsorption onto chrysotile and lizardite. The maximum adsorption capacities of MB for chrysotile and lizardite were found to be 352.97 and 254.85, respectively. Kinetic studies reveal that the pseudo-first-order model best describes the adsorption process. Thermodynamic analysis suggests an exothermic and spontaneous process. Statistical physics models further elucidate the monolayer nature of adsorption. Additionally, an artificial neural network is developed, exhibiting high predictive capability during training and testing stages. The reusability of chrysotile and lizardite is demonstrated through multiple regeneration cycles, maintaining substantial adsorption potential. Therefore, this research provides comprehensive insights into the adsorption characteristics of chrysotile and lizardite, emphasizing their potential as effiective and reusable sorbents for MB uptake from wastewater.

Influence of solution acidity on growth kinetics, structure and magnetic properties of Co-P films, obtained by chemical deposition

The results of studies of the effect of solution acidity on the growth kinetics, structure and magnetic properties of Co-P films obtained by chemical deposition are presented. It was shown that the growth of Co-P films in the low pH region occurs mainly due to the growth of crystallite sizes, and in the high pH region, due to an increase in the nucleation rate. From the analysis of the chemical equilibrium of redox reactions, taking into account the balance of citrate and hydroxyl complexes of Co, a qualitative explanation of the features of the change in the rate and nature of the deposition of Co atoms from pH is proposed.

Hydroxyapatite particles as carriers for 223Ra

Systematic investigation of optimal conditions for preparation and in vitro stability of HAP particles labeled with 223Ra, that could be considered as promising candidates for targeted α-therapy, has been carried out. Two different approaches to HAP labelling were tested: sorption of Ra2+ on pre-synthesized HAP-particles and incorporation of Ra2+ into the structure of HAP during its synthesis. Two textural forms of HAP particles were used—nanoparticles and particles with the diameter of 350 ± 20 μm. Kinetics of 223Ra sorption on HAP of different particle size and desorption in 0.9 % NaCl solution were studied. The influence of solution acidity and solid to liquid phase ratio on sorption of Ra was evaluated and the sorption yield up to 98 % was achieved. It was found that the optimal conditions for the sorption included synthesis of HAP nanoparticles in the presence of 223Ra at pH values of 4–7 followed by annealing at 900 °C. In this case subsequent cumulative desorption of Ra was <5 % of initial activity.

Influence of Solution Acidity on Structure of Actinocin Derivatives and Their Affinity to DNA Studied as a Function of pH by Raman Spectroscopy

ABSTRACT An important problem of molecular biophysics is the influence of pH and ionic strength of a solution on chemical structures and charge of biologically active substances. By means of pH titration and Raman spectroscopy methods, the influence of solution acidity on structural changes of actinocin derivatives was investigated, analogues to antitumor antibiotic actinomycin D. It has been shown that these ligands have different values of cation charges in neutral solutions. From analysis of Raman spectra, it was concluded that protonation of nitrogen atom and amino group of the phenoxazone ring starts only at pH < 3.5. It was shown that protonation of actinocin derivative with two amide groups (diaminoactinocin) occurred in two steps. Corresponding protonation constants for diaminoactinocin (log k 1 = 6.9 ± 0.5 and log k 2 = 5.3 ± 0.1) and for partially protonated actinocin derivative with three methylene groups in the side chains (log k = 5.3 ± 0.1) were obtained. Characteristic frequencies of Raman spectra for the basic functional C=O, C2–NH2, C–C=C, and –N=C groups of phenoxazone chromophore of actinocin derivatives in protonated and nonprotonated states were determined. The different affinities of binding of variously charged ligands to DNA have also been demonstrated.

Effect of acidity on microstructure and spectroscopic properties of Y 2O 3:Eu 3+ powders and ceramics

Y 2O 3:Eu 3+ nano-powders were synthesized by homogeneous precipitation and the influence of solution acidity was investigated. IR and TG–DTA analysis showed that in different acidic solutions different kinds of sediments were generated. TEM images revealed distinct morphologies of obtained powders. The resultant powders were sintered into ceramics in vacuum and then in N 2 atmosphere without any additives. SEM images indicated that the morphologies of powders have significant impact on the microstructures of sintering-derived ceramics. Low-agglomerated and uniform powders were in favor of production of ceramics with homogeneous microstructures. Excitation and emission spectra of both powders and ceramics were measured and some changes were observed.

Sorption of Ga (III) on Flexible Open Cell Polyurethane Foam of Polyether Type Impregnated with Tri-N-Buthyl Phospate

The obtained results concerning the Ga (III) ion retention on flexible open cell polyurethane foam of polyether type pretreated with tri-n-butyl phosphate are presented. The influence of solution acidity, phases contact time, Ga (III) concentration and solution temperature have been investigated. The parameters of Ga (III) batch sorption have been optimized. On the basis of Langmuir isotherms, the sorption constants and the thermodynamic parameters, ∆G, ∆Η and ∆S have been calculated.

Influence of solution acidity and CaCl 2 concentration on the removal of heavy metals from metal-contaminated rice soils

Soil washing is considered a useful technique for remediating metal-contaminated soils. This study examined the release edges of Cd, Zn, Ni, Cr, Cu or Pb in two contaminated rice soils from central Taiwan. The concentrations exceeding the trigger levels established by the regulatory agency of Taiwan were Cu, Zn, Ni and Cr for the Ho-Mei soil and Pb for the Nan-Tou soil. Successive extractions with HCl ranging from 0 to 0.2 M showed increased release of the heavy metals with declining pH, and the threshold pH value below which a sharp increase in the releases of the heavy metals was highest for Cd, Zn, and Ni (pH 4.6 to 4.9), intermediate for Pb and Cu (3.1 to 3.8) and lowest for Fe (2.1), Al (2.2) and Cr (1.7) for the soils. The low response slope of Ni and Cr particularly for the rice soils make soil washing with the acid up to the highest concentration used ineffective to reduce their concentrations to below trigger levels. Although soil washing with 0.1 M HCl was moderately effective in reducing Cu, Pb, Zn and Cd, which brought pH of the soils to 1.1 ± 0.1 (S.D.), the concurrent release of large quantities of Fe and Al make this remediation technique undesirable for the rice soils containing high clay. Successive washings with 0.01 M HCl could be considered an alternative as the dissolution of Fe and Al was minimal, and between 46 to 64% of Cd, Zn, and Cu for the Ho-Mei soil and 45% of Pb in the Na-Tou soil were extracted after four successive extractions with this dilute acid solution. The efficacy of Cd extraction improved if CaCl 2 was added to the acid solution. The correlation analysis revealed that Cr extracted was highly correlated ( P < 0.001) with Fe extracted, whereas the Cu, Ni, Zn, Cd or Pb extracted was better correlated ( P < 0.001) with Al than with Fe extracted. It is possible that the past seasonal soil flooding and drainage in the soils for rice production was conducive to incorporating Cr within the structure of Fe oxide, thereby making them extremely insoluble even in 0.2 M HCl solution. The formation of solid solution of Ni with Al oxide was also possible, making it far less extractable than Cd, Zn, Cu, or Pb with the acid concentrations used.

Sorption of REEs and TPEs on Sorbents Containing Ferrocyanide and Ferricyanide Ions

The sorption characteristics of anion exchangers of various structures, containing ferrocyanide and ferricyanide ions, with respect to REEs and TPEs was studied under static and dynamic conditions. It was shown that, in sorption of REEs, the ion-exchanger capacity with respect to ferrocyanide ions is fully used. The influence of solution acidity on sorption of REEs and TPEs was studied. Anion exchangers containing ferricyanide ions do not sorb REEs but sorb Am.

Coupled Redox and pH Potentiometric Responses of Electrodes Coated with Polypyrrole

ABSTRACT The coupled influence of solution acidity and redox electrolytes on the open-circuit potentials of polypyrrole-modified electrodes was studied by recording the potential vs. time dependencies. It was observed that doping anions affect the relative rate of the responses resulting from pH influence (pH response) and from the presence of a redox couple in the solution, such as Fe(III)/Fe(II) or Fe(CN)63-/4-(redox response). Separation of the pH and redox responses was possible for polypyrrole doped with large organic anions of weak acids (Tiron, sulphosalicylic acid, Indigo Carmine). In such cases, a very fast pH response was recorded after which the polymer potential relaxed to the solution redox potential in each case. The final stable potential was determined entirely by the potential of the redox couple in solution. The final potential was pH-independent unless the redox potential was influenced by solution acidity. The solution pH determines only the shape of the potential vs. the time dependence, e.g. much faster responses were observed for solutions with a higher H* concentration.

Influence of solution acidity on the adsorption and charge transfer kinetics of parabanic acid reduction

Parabanic acid reduction has been studied in the − 1.4 ⩽ H0 ⩽ 0.9 acidity range by the ac impedance technique. Changes in the adsorption of reactant and products with solution acidity lead to protonation equilibrium constants that differ from their bulk values. The observed pKa shifts were consistent with interfacial dielectric saturation. Variation of the charge transfer parameters with potential and proton activity allows a detailed analysis of the reduction mechanism to be performed in terms of the scheme of squares.

ON THE STUDIES OP MOLYBDENUM (VI) SORPTION ON TITANIUM PHOSPHATE 'S ION EXCHANGERS

Abstract Mo (VI) sorption on the inorganic Ion exchangers on amorphous titanium phosphate and hydrous titanium dioxide was studied. The influence of solution acidity, Mo(VI) concentration In a solution, P:T1 mole ratio in a sorbent and the presence of various anions In solution was Investigated. Mo-contalnlng lonites, as a result of a sorption process, were studied for the purification of water and Ringer’s solution, contamlned with Cs 137 Ions. Obtained sorbents were examined In solutions with some transition metals and alkaline earth metals. Also IR spectrophotometry studies were carried out. It was found that the process of Mo (VI) sorption on titanium hydroxophosphate occurred mainly according to an anion exchange mechanism and did not Improve upon the ion-exchange properties of the Initial lonites. Obtained caesium uptake characteristics demonstrated the absence of surface heteropolycompounds in titanium hydroxophosphate treated by Mo(VI)-compounds.

Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters, the model compounds resorcinol diacetate and resorcinol dimethyl ether

Chlorination of seawater containing resorcinol diacetate or resorcinol dimethyl ether results primarily in the formation of brominated products. At low chlorine concentrations (cf. model compound), ring substitution products dominate whilst at higher chlorine levels ring cleavage occurs and trihalomethanes are produced. Electrophilic chlorination of the model compounds in seawater therefore appears to be slower than the formation of HOBr by oxidation of naturally occurring bromide. The influence of solution acidity on the nature and extent of halogenation is described and reaction mechanisms postulated.