From an Al4-Cluster to Al+ Complexes: Lessons on Metalloidal Clustering

Low-valent aluminium compounds are among the most reactive and widely researched main-group compounds. Since the isolation of [(AlCp*)4] in 1991 as the first stable, molecular AlI compound, a variety of highly reactive neutral or anionic low-valent aluminium complexes were developed. In particular, the strongly basic aluminyl anions allowed for nucleophilic activation of a large variety of small molecules and formation of elusive transition-metal complexes. By contrast, an accessible cationic, low-valent aluminium compound combining the nucleophilicity of low-valent compounds with the electrophilicity of aluminium is hitherto unknown. Here, we report the synthesis of [Al(AlCp*)3]+[Al(ORF)4]– (RF = C(CF3)3) via a simple metathesis route. Unexpectedly, the complex ion forms a dimer in the solid state and in concentrated solutions. Addition of Lewis bases results in monomerization and coordination to the unique formal Al+ atom giving [(L)xAl(AlCp*)3]+ salts with L = hexaphenylcarbodiphosporane (cdp; x = 1), tetramethylethylenediamine (tmeda; x = 1) and 4-dimethylamino-pyridine (dmap; x = 3). Depending on the donor strength of the ligand added, the Al+–AlCp* bonds in the [(L)xAl(AlCp*)3]+ cluster cations can be finely tuned between very strong (L = nothing) to very weak and approaching isolated [Al(L)3]+ ions (L = dmap). We anticipate our easily accessible low-valent aluminium cation salts to be the starting point for investigation and potential application of this unusual compound class. In particular, the ambiphilic reactivity of the cationic, low-valent compounds will be studied. Moreover, knowledge gained from the stabilization of the reported complex salts is expected to facilitate the isolation and application of novel cationic, low-valent Al complexes.

Creation of a combined system for treatment of iron-containing wastewater from etching operations

The object of research is the methods of purification of iron-containing wastewater from etching operations, the subject of the study is spent technological solutions of etching and wastewater from the operations of washing enterprises of hardware products. Spent etching solutions are characterized as highly concentrated solutions, and wash water belongs to the category of concentrated solutions containing toxic impurities: heavy metal ions, acids, surfactants. The main problem in the etching area is the processing of used etching solutions. The most progressive creation of combined systems in which the bulk of wastewater is treated in centralized systems with partial return of water to the production process. With such wastewater treatment, the problem arises of reducing the total concentration of iron to less than 1 mg/l. That is why, in accordance with the requirements of environmental legislation on nature management, there is a need for deep additional treatment of such wastewater. The study used the methods of potentiometric titration and chemical deposition, as well as the method of photometric determination. Magnetic cleaning was studied in an experimental magnetic deposition apparatus. The paper presents the results of studies evaluating methods for purifying iron-containing wastewater from etching operations. Improvement is achieved by the creation of technological combined schemes for the purification of iron-containing wastewater, including a magnetic device as an auxiliary element. At the same time, the main volume of wastewater is treated in centralized systems with a partial return of water to the production process. Waste solutions from etching operations are subject to regeneration with return to the production process and partial dosage into the main wastewater stream from washing operations. Deep purification from iron-containing impurities using a magnetic device expands the possibilities of practical implementation of reverse osmosis to obtain «clean» water in centralized systems. This water is applicable for the preparation of process solutions and mixed with industrial water for flushing operations.

Copper Chloro-Complexes Concentrated Solutions: An Electrochemical Study

Basic studies on concentrated solutions are becoming more and more important due to the practical industrial and geological applications. The use in redox flow batteries is one of the most important applications of these solutions. Specifically, in this paper we investigated high-concentrated copper chloro-complexes solutions with different additives. The concentration of ligands and additives affects the physicochemical and electrochemical properties of 2 M solutions of Cu(I) and Cu(II). Solutions with calcium chloride and HCl as Cl− source were investigated with Cu:Cl ratios of 1:5 and 1:7, the 1:5 Cu:Cl ratio being the best performing. The substitution of calcium chloride with ammonium chloride increased the conductivity. However, while the effect on the positive electrode process was not very evident, the reversibility of the copper deposition–stripping process was greatly improved. Orthophosphoric acid could be a viable additive to decrease the complexation of calcium with chloride anions and to improve the stability of Cu(II) chloro-complexes. Absorption spectroscopy demonstrated that phosphate ions do not coordinate copper(II) but lead to a shift in the distribution of copper chloro-complexes toward more coordinated species. Electrochemically, the increased availability of chloride anions in solution stabilized the Cu(II)-rich solution and led to increased reversibility of the Cu(II)/Cu(I) redox process.

Solvent-Free Visible Light Photocatalytic Oxidation Processes Mediated by Transparent Films of an Imine-Based Organic Polymer

Reaction between concentrated solutions of phenotiazine containing trialdehyde building block 4,4′,4″-(10-phenothiazine-3,7,10-triyl)tribenzaldehyde and (1R,2R)-cyclohexane-1,2-diamine results in the formation of a yellow transparent film. Exhaustive characterization of this material indicates that it is the result of the assembly of a linear polymer resulting from the linking of imine-based macrocycles. Phenotiazine units confer to this plastic the optical properties characteristic of photocatalytic materials. The transparency of the obtained material enabled the performance of solvent-free photocatalytic processes. This concept is illustrated by the oxidation of liquid organic sulfides, which can be performed in a recyclable manner. According to selective quenching experiments, such processes are the result of the energy transfer to oxygen molecule, generating singlet oxygen that is able to activate the sulfide molecules directly.

Gel Formation in Low Concentrated Solutions of Glycyram and Amino Acids in the Presence of Silver Nitrate

Research relevance: low molecular weight supramolecular hydrogels are unique objects that can solve many pressing problems in medicine, food industry and other sectors of the national economy. Research objectives: in recent past, it was discovered that low-concentration solutions of L-cysteine and silver nitrate (CSN) can form, when electrolyte solutions are added to hydrogels. We were faced with the task of obtaining hydrogels from dilute solutions of glycyram (GC) by adding CSN, since GC, due to its poor solubility, has low bioavailability. Materials and research methods: using the method of isomolar series, a comparative study of the formation of hydrogels by dilute GC solutions with the addition of CSN and GCP was carried out. It has been found that most durable hydrogels were obtained using CSN. Thus, GC hydrogels were obtained at a concentration of 10−3 M after adding CSN and GCP, which have a supramolecular character and combine the properties of GC, amino acids, and silver ions. Research results: glycyram hydrogels were obtained at its concentration equal to 10−3 M by mixing it with silver amino acids L-cysteine (CSN) and L-glutamic acid (GCP) solutions in same low concentrations. Conclusions: hydrogels with glycyram form silver solutions of those amino acids that are capable of giving frame structures at a ratio of amino acid: silver nitrate of 1.25.

Comparative study on Biochar salt absorption capacity in different saline concentrated solutions

Salt-affected soils are caused by excess accumulation of salts. As soil salinity increases, salt effects can result in the degradation of soils. Previous studies have determined that biochar has the potential to reduce salt stress in soils. In this study, the electroconductive properties of biochar to adsorb salts were investigated in different saline-concentrated solutions. Pelletized, fragmented and powdered biochar were placed in solutions with concentrations of 0, 50, 500, 1000, and 2000 parts per million sodium chloride, respectively. Control treatments consisted of deionized water mixed with salt and no biochar addition. A week after setting the experiment, the electroconductivity measurements were significantly higher relative to the first day. Significant differences were observed among treatments for pelletized, fragmented, and powdered biochar treatments. Increases in electroconductivity values are attributed to ambient temperature changes and differences in particle size. However, pelletized biochar declined in electroconductive values, which is attributed to ions being retained inside the pores of bigger particles. Our study concludes that biochar can adsorb salts at lower sodium chloride concentrations; therefore, it may help mitigate soil salt stress.

Concentration-Dependent Fluorescence Emission of Quercetin

Quercetin (Q) is an important antioxidant with high bioactivity and the potential of being used as SARS-CoV-2 inhibitor. The fluorescence (FL) emission from Q solutions made with different polar and non-polar solvents (methanol, acetone, and chloroform) was measured and compared with the FL emission from Q powder and from Q crystals. In the FL spectra of the solutions with high Q concentration, as well as in the spectra of Q in solid state, two features, at 615 nm and 670 nm, were observed. As the solution concentration decreases, the intensity of those peaks decreases and a peak at 505 nm arises. The FL emission of low concentration solutions displayed only that peak. Calculations for the Q molecule in each solvent, performed using time-dependent density functional theory (TDDFT), show that the emission at 505 nm is associated with the excited state intramolecular proton transfer (ESIPT) of the –OH3 group proton. Our calculations also show that the feature at 615 nm, which is observed in solid state Q and also in the emission of the high concentrated solutions, is related to the –OH5 proton transfer.

Successful Development and Deployment of a Novel Chemical Package for Stimulation of Injection wells, Offshore UK

The work described in this paper details the development of a single stimulation package that was successfully used for treating an offshore horizontal polymer injection well to improve near wellbore injectivity in the Captain field, offshore UK. The practice was to pump these concentrated surfactant streams using multiple pumps from a stimulation vessel which is diluted with the polymer injection stream in the platform to be injected downhole. The operational challenges were maintaining steady injection rates of the different liquid streams which was exacerbated by the viscous nature of the concentrated surfactants that would require pre-dilution using cosolvent or heating the concentrated solutions before pumping to make them flowable. We have developed a single, concentrated liquid blend of surfactant, polymer and cosolvent that was used in near-wellbore remediation. This approach significantly simplifies the chemical remediation process in the field while also ensuring consistent product quality and efficiency. The developed single package is multiphase, multicomponent in nature that can be readily pumped. This blend was formulated based on the previous stimulation experience where concentrated surfactant packages were confirmed to work. Commercial blending of the single package was carried out based on lab scale to yard scale blending and dilution studies. About 420 MT of the blend was manufactured, stored, and transported by rail, road and offshore stimulation vessel to the field location and successfully injected.