Development of Electroflotation Technology for Extraction of Anionic Surfactants and Nonferrous Metal Ions from Wastewater Produced at Electroplating Industries

Sorption extraction of anionic surfactants NaDDS and NaDBS on freshly formed iron(III) and aluminum(III) hydroxides and on a highly dispersed activated carbon of OU-B brand was experimentally studied. It was shown that NaDDS is the most fully sorbed on Al(OH)₃ and OU-B, whereas on Fe(OH)₃, the maximum sorption is observed for NaDBS. The electroflotation extraction of anionic surfactants and poorly soluble iron(III) and aluminum(III) hydroxides was examined and the influence exerted by the following factors (pH, nature of electrolyte, surfactant concentration) on the degree of extraction of these substances was analyzed. In addition, electroflotation extraction of OU-B in the presence on nonferrous metal hydroxides and surfactants of varied nature from aqueous solutions was performed. The results obtained were used to develop a technological scheme for electroflotation of complex-composition wastewater.     

Raising the efficiency of electroflotation purification of wastewater formed in production of printed-circuit boards to remove copper ions in the presence of complexing agents,surfactants, and flocculants

It was found that the solution composition, pH value, concentration, and nature of surfactants and flocculant affect the process of electroflotation extraction of copper hydroxide in the presence of an excess amount of ammonia. A relationship between the ζ-potential of the dispersed phase and the degree of copper extraction was found. It is shown that a cationic surfactant and flocculants positively affect the efficiency of the electroflotation extraction of copper. Under the optimal conditions, the degree of the electroflotation extraction reaches values of 95–96%, and that with additional filtration, 97–99%. A technological scheme for implementing the electroflotation process is suggested.     

Electroflotation Extraction of Valuable Components from Wash Waters of Electroplating Works,with Water Recycling

An electroflotation technology for extracting ions of heavy nonferrous metals from the wash and waste waters of electrolytic baths is proposed. The main regularities and basic parameters of the electroflotation extraction of ions of copper, zinc, nickel, chromium, and iron in the form of hydroxides, phosphates and sulfides of the metals are determined. Optimum technological parameters for the extraction of copper ions in the presence of complexing agents are established. Advantages of an electroflotation with electrocorrection of pH are shown.     

Experimental studies of the efficiency of electroflotation recovery of poorly soluble lanthanum compounds from aqueous solutions

Features of electroflotation recovery of poorly soluble lanthanum compounds from aqueous solutions containing sodium salts were experimentally determined and studied for the first time. The role was identified that anionic, cationic, and nonionic surfactants added to various supporting electrolytes (sulfate, chloride, carbonate, nitrate) play in the efficiency of electroflotation recovery of poorly soluble lanthanum compounds. The possibility of electroflotation recovery of lanthanum hydroxide with an efficiency of 95–99% was experimentally and theoretically substantiated.     

Electroflotation Recovery of Poorly Soluble Lanthanum Compounds from Highly Concentrated Salt Systems

Electroflotation of poorly soluble lanthanum compounds from model solutions simulating with high accuracy highly concentrated industrial salt systems was studied. The influence of various kinds of microadditives (flocculants and surfactants; cationic, anionic, and nonionic) on the efficiency of the recovery of lanthanum compounds from highly concentrated salt solutions was examined. For each supporting electrolyte (chloride, carbonate, sulfate, oxalate, nitrate), additives intensifying the process and enhancing its efficiency were found. The mean size and ζ-potentials of the dispersed phase particles were measured to account for the degrees of recovery reached in lanthanum electroflotation. A design of an installation for lanthanum recovery, allowing solution processing on the commercial scale, was suggested.     

Chromium removal technologies

Chromium can exist in different oxidation states (e.g. 0, III, VI). Chromium can be both beneficial and toxic to animals and humans depending on its oxidation state and concentration. At low concentration, Cr(III) is essential for animal and human health. Chromium(VI) compounds are highly soluble, mobile and bioavailable compared to trivalent chromium. Chromium(VI) is dangerous for humans due to its toxicity and carcinogenic properties. The presence of hexavalent chromium in waste water is a potential hazard to aquatic animals and humans. Various methods are adopted for the removal of hexavalent chromium from industrial effluents. Among these different techniques, biosorption is the most promising one. In this process, the various components present in biomaterial reduce the toxic hexavalent chromium to non-toxic trivalent chromium. Algae, fungi and bacteria have biosorption properties, and cell walls are responsible for biosorption of dead biomaterial. But this process removes chromium from waste water very slowly. So for chemical modification of biosorbents, optimization of biosorption parameters is required to increase the effectiveness of this process.     

Selective separation and extraction of copper(II), iron(II,III), and Cerium(III,IV) ions from aqueous solutions by electroflotation method

Possibility of the electroflotation separation and extraction of cerium(II, IV), copper(II), and iron(II, III) from aqueous solutions is demonstrated. The optimal pH value and the concentration ratio of ions of the metals being separated, at which their electroflotation separation and extraction from aqueous solutions is the most efficient, was determined. It was shown that the electroflotation method is promising for selective separation and extraction of metal ions with various hydrate-formation pH values from aqueous solutions.     

Analytical chemistry of chromium species in the environment, and interpretation of results

Valence-selective species determination of chromium in environmental and biological material presents intricacies primarily due to the complex nature of the samples and the instability of the oxidation states of chromium. In particular organic matter ubiquitously present in environmental samples introduces the risk of chromium(VI) reduction during analysis which takes place preferably in acidic solution. Also chromium(III) oxidation may occur in alkaline medium. Hence analytical methods should be adequately adapted to the reliable determination of chromium(VI) in blood, natural water, effluents, sediments and soil. It can be shown that polarography is most effectually suitable to the determination of chromium(VI) compounds. Chromium(VI) is electrochemically active over the entire pH range, so that medium pH can be selected for measuring, thus protecting samples most effectively from undergoing redox reactions during the analytical procedure. Other established methods such as spectrophotometry or valence-specific extraction are more crucial, because these generally require acidic medium. In some cases sample pre-treatment can be employed to eliminate reductants prior to final measurement. Very few methods are available to selectively measure chromium(III). Indirect determination is therefore preferred. Optimum conditions for the determination of total chromium by AAS are shortly outlined.     

Regularities of complexation in the series of sorbents on the polystyrene matrix and their complexes with chromium(III) and manganese(II)

The physicochemical properties of polymeric complexing sorbents with the o,o′-dihydroxy-(1-azo-1′)-functional complexing group were studied. Optimal sorption parameters for chromium(III) and manganese(II) (medium acidity, temperature, time), the sorption capacity of the sorbents, and the stability constants (pK _a′)of the complexes were determined. Correlation relations were established between the dissociation constants (pK _a′) of the sorbent functional group and pH₅₀ of the complexation of the considered elements; between and the stability of the formed complexes (logβ); and between pK _a′ and the deprotonation energy (E _depr) of the sorbent hydroxy group located in the para-position to the introduced substituent. The established correlation relations are useful for targeted prediction of the physicochemical parameters of the sorbents, their complexes, and the sorption of manganese(II) and chromium(III) aimed at recovery and pre-concentration of these ions from objects with various chemical composition.     

Combination of ultrasound and discarded tire rubber: removal of Cr(III) from aqueous solution

Ground discarded tire rubber is an interesting and inexpensive medium for the sorption of toxic metals, including chromium, from water. The batch sorption tests were conducted to investigate the sorption capacity of Cr(III) from aqueous solution by ground tire in the presence and absence of ultrasound. The research parameters included ultrasonic waves, solution temperature, aqueous chromium concentration, particle size of the ground tire, contact time, and others. The Langmuir model was applied to the sorption equilibrium to determine the maximum metal sorption capacity in the presence and absence of ultrasound. The Langmuir constants were also obtained from the isotherms under different conditions. The results indicated that the tire rubber was a more efficient sorbent for the removal of chromium in the presence of ultrasound. Because there are several stages in the sorption process, it is important to find out which step or steps control the rate of sorption. According to the results, the internal porous diffusion is the rate-controlling step. The diffusion coefficient of Cr(III) in ground tire rubber in the presence of ultrasound was about two times greater than that in the absence of ultrasound. The effect of ultrasound on the sorption process could be explained by the thermal and nonthermal properties of acoustic cavitation.     

Raising the Efficiency of Electroflotation Extraction of Metals in Multicomponent Systems from Aqueous Media

Specific features of the electroflotation extraction of hydroxides of nonferrous metals (Cu²⁺, Ni²⁺, Zn²⁺, Cr³⁺, Fe³⁺) from a five-component system in the presence of sodium sulfate as supporting electrolyte were examined. The fundamental aspects of the extraction process upon introduction into the system of surfactants of varied nature and flocculants were determined. It was shown that addition of a nonionogenic flocculant N-300 makes it possible to raise the efficiency and stabilize the process of the electroflotation extraction of difficultly soluble metal hydroxides contained in multicomponent systems from wastewater formed in various galvanic shops, with the degrees of extraction possibly reaching a value of 97%.     

Enhanced dissolution of oxcarbazepine microcrystals using a static mixer process

The purpose of this study was to form micronized powders of Oxcarbazepine (OXC), a poorly water-soluble drug, using a static mixer technique to enhance the dissolution rate. Controlled precipitation was achieved injecting the organic OXC solution rapidly into an aqueous methylcellulose (MC) protective solution by means of a static mixer thus providing turbulent and homogeneous mixing. Furthermore, a factorial design was implemented for data analysis. The physicochemical properties of the freeze-dried dispersions were evaluated by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Drug microcrystals showed a narrow size distribution with approximately 2 μm mean particle size and high drug loading. DSC and FTIR studies revealed that the drug remained in crystalline state and no drug–polymer interaction occurred. The dissolution studies showed enhanced dissolution of OXC microcrystals compared to the pure drug. The static mixer technique was proved capable for micro-sized polymeric particles. This is an inexpensive, less time consuming and fully scalable process for development of poorly soluble drugs.     

The effect of Cr(III)-organic complexes on the determination of inorganic chromium species in groundwater by ammonium pyrrolidinedithiocarbamate–methylisobutylketone extraction procedure

Groundwater samples collected from a tannery contaminated area were analyzed for chromium species with the objective of investigating the interference of Cr(III)-organic complexes in the determination of Cr(VI) using APDC–MIBK extraction procedure. The contribution of Cr(III), Cr(VI) and Cr(III)-organic complexes towards total chromium ranged between 2 and 61%, 27 and 86%, and, 6 and 23%, respectively. The Cr(III)-organic complexes were not extractable by APDC–MIBK, however, HNO₃ digestion released the organic bound Cr(III). Interference of organic bound Cr(III) in Cr(VI) determination due to MIBK soluble Cr(III) was not observed. Significant difference between total dissolved chromium determined after appropriate digestion procedure, and the sum of dissolved Cr(III) and Cr(VI) determined indicates the presence of the Cr(III)-organic complexes. MIBK extraction of samples without APDC is an useful way to check the extractability of organic bound Cr(III). The presence of soluble Cr(III)-organic complexes thus add complexity to chromium speciation analysis by APDC–MIBK procedure.     

Synthesis,characterization and antibacterial studies of Tm(III), Yb(III) and Lu(III) complexes of morin

New solid amorphous compounds of Tm(III), Yb(III) and Lu(III) with morin have been synthesized. Their composition and some physicochemical properties have been studied by elemental analysis, thermogravimetric analysis, IR spectroscopy as well as by conductivity, UV/Vis, MS, and NMR spectroscopies in solution. The spectroscopic studies have indicated that the 3-OH hydroxyl group and the carbonyl oxygen of morin were involved in the coordination of metal ion. The antibacterial activity of the synthesized compounds has been determined by the cylinder-plate diffusion and dilution methods (determination of minimum inhibitory concentration).     

Physicochemical properties of 4-tert-butylbenzoic acid N′,N′-dialkylhydrazides

Properties of hydrazides of 4-tert-butylbenzoic acid, important for their application in extraction technology, have been studied: solubility, acid-base properties, distribution between immiscible liquids, and hydrolytic stability. pH ranges of existence of different forms of the compounds have been determined. The N′,N′-dialkyl derivatives with alkyl chains longer than C₆ are readily soluble in nonpolar solvents, are not transferred into aqueous phase, and are stable with respect to hydrolysis in acidic and basic media. Linear correlations of the studied physicochemical parameters with the compounds structure and the medium properties have been elucidated.     

Effect of Surfactants and Carbon Nanomaterials on the Electroflotation Extraction of the Disperse Phase of Cobalt Hydroxides

The effect of surfactants and carbon nanomaterials (CNMs) on the electroflotation extraction of the disperse phase of cobalt(II) and (III) hydroxides at pH 6 and pH 10 was studied. It is shown that at pH 6 in the absence of surfactants, the efficiency of cobalt extraction in various electrolytes is low and does not exceed 15–25%. In the surfactant–CNM–electrolyte system, the degree of extraction α increases in the chloride, nitrate, and sulfate solutions compared with the solutions containing no surfactants. The electroflotation extraction of cobalt was more efficient at pH 10: α reached 80–96% in the absence of surfactants, 70–97% in the surfactant–electrolyte system, and 60–97% in the surfactant–CNM–electrolyte system. The optimum conditions of the electroflotation extraction of cobalt hydroxides from solutions containing various inorganic electrolytes were determined. The effect of the sodium chloride content on the degree of cobalt extraction at pH 6 was studied. When the NaCl concentration increased from 0 to 10 g/L, the efficiency of cobalt extraction increased to 92%; when the flocculant was added and an additional stage of filtration was used, cobalt was extracted almost completely.     

Pigments based on thermally treated iron-containing slimes

The effect exerted by chemical and phase composition on the color characteristics of the products of a heat treatment of slime obtained at purification of model wastewaters containing prescribed amount of zinc(II), nickel(II), copper(II), and chromium(III) compounds using ferroferrihydrosol was studied. The dependence of pigment properties of the products of the heat treatment of slimes on the concentration of metal compounds in them was determined.     

Chromium(III) and Chromium(IV) Tetraphenylporphine Complexes

Stable chromium complex (AcO)CrTPP was synthesized through the reaction of meso-tetraphenylporphine with chromium(III) acetate in boiling phenol. Coordination properties of chromium porphyrin in reaction with imidazole and pyridine in o-xylene were studied by electronic absorption spectroscopy and computer modeling. A single-electron oxidation of chromium(III) complex was found to be affected by peroxide compounds. The stability of an extra complex depends on the basic properties of the extra ligand and oxidation number of the central metal atom. The complex stability correlates with the calculated energy of formation of the metal–extra ligand bond. The geometrical structure and energy parameters of hexacoordinated chromium porphyrins were calculated using the quantum-chemical method. The effect of the cis and trans position of ligands in the composition of a macrocyclic compound was established to be significant only in the extra complexes (AcO)CrTPP.     

Electrodeposition of chromium-molybdenum alloy from electrolyte based on chromium(III) sulfate

The conditions of chromium-molybdenum plating from the electrolytes based on chromium(III) compounds are studied. It is shown that the deposits containing to 2 wt % molybdenum can be obtained by introducing sodium molybdate into the composition of electrolytes based on chromium(III) compounds. The introduction of molybdenum into the composition of chromium electrodeposits enhances their corrosion resistance in the media containing chloride ions.     

A Review of Temperature Influence on Adsorption Mechanism and Conformation of Water Soluble Polymers on the Solid Surface

The temperature effect on adsorption behavior of water soluble polymer and structure of its adsorption layer formed on the solid surface is presented. The main reasons for such problem explanation are wide application possibilities of stabilization-flocculation properties of polymers in many technological and ecological processes and very poor knowledge about temperature dependences of high-molecular compounds adsorption on the solid surface. To systematize the information about the effect of temperature on polymer chain conformation on the adsorbent surface the following aspects were considered: thermodynamic and physicochemical characteristics of polymer solutions, stabilization-flocculation properties of polymers in the dispersed systems, and presentation of respective experimental results. The theoretical and experimental evidence of the temperature effect on polymer macromolecule conformation on the solid surface presented in the article can contribute to better knowledge and understanding of the adsorption process at the metal oxide-polymer solution interface in the temperature function.