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.     

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%.     

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.     

Physicochemical efficiency of electroflotation of finely divided carbon nanomaterial from aqueous solutions containing surfactants

Electroflotation of finely divided carbon nanomaterials—carbon nanoflakes (CNFls)—from aqueous solutions with a wide pH range of 3.0 to 11.0 in the presence of surfactants of various types was studied experimentally. The efficiency indices were determined for the electroflotation of CNFls from CNFls–surfactant–Na₂SO₄ solutions in the presence of a coagulant (iron(III) chloride) and flocculants, which enabled one to find the optimal conditions for electroflotation of carbon nanomaterials.     

Separation of phenols from aqueous micellar solutions by cloud point extraction

The cloud point technique was used to recover phenol, 4-methylphenol, and 4-nitrophenol from aqueous solutions using oxyethylated methyl dodecanoates as nonionic surfactants. Oxyethylated methyl dodecanoates are convenient nonionic surfactants for such separations. Their cloud points can be easily modified by a change in surfactant hydrophilicity or by the addition of a second nonionic surfactant and/or an electrolyte. The use of the hydrophile lipophile balance is preferred to model the cloud point of oxyethylated methyl dodecanoates and their mixtures with other surfactants. The composition of the surfactant-rich phase depends on electrolyte type and the overheating. The phase can contain only 5-15% of water. Recovery of phenols changes in the order 4-nitrophenol >4-methylphenol > phenol and is increased in the presence of sodium chloride. The presence of salting-out electrolytes is preferred both to decrease the cloud point and to increase the efficiency of extraction.     

Effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant and a cationic conventional (monomeric) surfactant

Herein we report the effect of (chloride salt) electrolytes on the mixed micellization of (equimolar) a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16), and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB) in aqueous solutions. In absence and presence of (chloride salt) MCl (where M?Li, Na, and K) electrolytes, the critical micelle concentration (CMC) of mixed (16-6-16 + CTAB) surfactants was measured by surface tension measurements. With increasing the concentration of electrolyte, the CMCs were increasing. The surface properties and the thermodynamic parameters of the mixed micellar systems were also evaluated. From these evaluated thermodynamic parameters, it was found that in presence of electrolyte the stability of the mixed micellar system is more.     

Experimental studies of interfacial phenomena on innovative carbon nanomaterials in aqueous electrolyte solutions

Interfacial phenomena on the surface of carbon nanomaterials (CNM) in aqueous solutions in the presence of surfactants were studied experimentally and theoretically. The hydrodynamic radius and electrokinetic potential of particles of the dispersed phase and the concentration of functional groups on the CNM surface were found. The points of zero charge of solutions of the dispersed phase were measured, and so were their shifts with varying electrolyte concentrations, which make it possible to determine the pH values at which the CNM particles are electrically neutral.     

Effect of the composition of the medium and electroflotation processing parameters on extraction efficiency of chromium(III) dispersed phase from aqueous solutions

Influence exerted by the composition of the medium (solution pH, ionic composition, presence of flocculants and surfactants), physicochemical properties of the dispersed phase (particle size, electrokinetic potential), and technological parameters of the electroflotation process (volume current density, magnetic treatment, solution temperature) on the efficiency of the electroflotation extraction of poorly soluble chromium(III) compounds from aqueous solutions was studied. It was shown that the extraction efficiency directly depends on the composition of the medium, which determines the physicochemical properties of poorly soluble chromium(III) compounds, and on the size of particles and their minimum surface charge. The optimal technological parameters of the electroflotation process are suggested.     

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.     

Adsorption of Cationic Surfactants on Silica Surface: 1. Adsorption Isotherms and Surface Charge

Adsorption isotherms of cationic surfactant, dodecylpyridinium chloride, on an Aerosil OX50 and isotherms of surface charge against the background of 0.001- and 0.1-M KCl solutions at pH 7 and 9 were measured and analyzed. Different forms of adsorption isotherms of surfactants at low and high electrolyte concentrations are explained from differences in the formation of the surface charge of Aerosil. Comparison of the isotherms of surfactant adsorption and surface charge allowed us to make conclusions about the surfactant orientation and structure of an adsorption layer, as well as to determine the fraction of surfactant molecules in the first and second adsorption layers.     

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.     

Effect of Surfactants on Electrodeposition of the Sn–Ni Alloy from Oxalate Solutions

The effects of surfactants on the electrolytic deposition of tin–nickel alloys from oxalate–ammonium electrolytes were determined. The adsorption of the nonionic surfactant at the interface decreases the rate of charge transfer across the interface. As a result, the electrochemical stage of the electroreduction of metals slows down, and the alloy is deposited in the form of shiny finely crystalline coatings. The range of optimum surfactant concentrations in the oxalate–ammonium electrolyte was determined based on the simulation of the interface impedance obtained during the alloy deposition and the electron microscopy studies of the obtained coatings.     

Effects of Salts on the Micellization of a Short-Tailed Nonionic Ethoxylated Surfactant: An Intradiffusion Study

In commercial formulations, surfactants are often co-formulated with inorganic electrolytes, which are included as inexpensive thickeners. Salts affect the surfactant’s aggregative and functional behavior. However, while the electrolyte effect on the self-aggregation of ionic surfactants can be rationalized in terms of electrostatic interactions, in the case of nonionic surfactants the molecular determinants are still unclear. In this work, we investigate the effects of alkali and alkaline–earth metal chlorides on the micellization of the nonionic surfactant hexyl penta(oxyethylene) ether, C₆E₅, in aqueous solution. To this aim, the C₆E₅ intradiffusion (also named self-diffusion) coefficient in aqueous mixtures of various alkali and alkaline–earth metal chlorides was measured by pulsed gradient spin-echo NMR. The results show that all the considered electrolytes cause a decrease of the surfactant critical micellar concentration, cmc, while the micellar size is almost unaffected. The experimental evidence can be interpreted in terms of de-hydration of the apolar alkyl tails with a minor contribution arising from the dehydration of the poly(ethylene oxide) headgroups. The order of effectiveness of the different cations follows the Hofmeister series, some aspects of which are briefly discussed.     

Microfiltration of amphoteric surfactant using ceramic membranes

The microfiltration of commercially available amphoteric surfactant using ceramic membranes has been investigated. Various combinations operating conditions such as pH, electrolyte and surfactant concentrations were employed. Zeta potential and adsorption isotherms were obtained for the components of membrane surfactant system as functions of pH using surfactant or indifferent electrolyte (KCl). The shift in the membrane isoelectric point induced by the surfactant is linked to the carboxylic groups present on the surfactant which are believed to play a dominant role in the net surface charge of the membrane. A minimum in the permeate flux was found at the pH corresponding to the isoelectric point of the zwitterionic surfactant. This behaviour is ascribed to the interactions occurring between the surfactant–surfactant molecules and the surfactant–membrane. The higher fluxes obtained at low pH as compared to high pH arise from different fouling mechanisms and ionic strengths. Lower fluxes were found when inorganic electrolytes were used in conjunction with surfactant. However, as the valency of the salt increases, flux behaviour of the zwitterionic surfactant (close to isoelectric point) does not vary whilst the cationic and anionic state of the surfactants are much more affected. Interactions between surfactant molecules as a result of the charge screening effects by the larger valence ions are encouraged. The permeate flux declines with an increasing surfactant concentration even though some concentrations fall under the critical micelle concentration (c.m.c.). This is attributed to concentration polarisation in which the accumulated surfactant concentration at the membrane surface could form a stable viscous phase which is resistant to permeate flow in the secondary layer next to the membrane surface. This paper demonstrates the role interactions such as surfactant–surfactant and surfactant–membrane play in influencing the filterability of surfactant solutions using ceramic membranes.     

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.     

Separation of nonionic surfactants of the polyoxyethylene type by capillary electrophoresis

 Nonionic surfactants are widely used in commercial formulations as complex mixtures requiring efficient and selective separation methods. Capillary electrophoretic separations were carried out in electrolytes containing high amounts of organic solvents and anionic surfactants based on the formation of association complexes between analytes and anionic surfactants without micelle formation. Octyl- and nonylphenol polyethoxylates were separated as their ethoxylate homologues. Influences of the electrophoretic conditions like electrolyte concentration and pH, type and content of anionic surfactant and organic solvents were investigated. Received: 12 February 1996/Revised: 21 May 1996/Accepted: 5 June 1996     

Investigation of the electrokinetic properties of paraffin suspension. 2. In cationic and anionic surfactant solutions

Electrical phenomena at nonionogenic hydrophobic surfaces (solid or liquid) in water, electrolyte, and/or surfactant solutions still attract research. In part 1 of this paper we described the electrokinetic behavior of paraffin wax suspension in water and electrolyte solutions (NaCl or LaCl3). On the basis of the latest data of water structure near hydrophobic surfaces it was concluded that immobilized water dipoles at the interface can play an essential role in the zeta potential formation. In this paper were investigated the zeta potentials of paraffin wax in cationic surfactants cetyltrimethylammonium bromide, C16H33(CH3)3NBr, and octadecyltrimethylammonium chloride, C18H37(CH3)3NCl, and anionic surfactant sodium dodecyl sulfate, C12H25SO4Na. Also changes in wettability of the paraffin surface due to the surfactant's adsorption were studied via wetting contact angle measurements and calculation of the surface free energy. It was concluded that at a low surfactant concentration (10(-6) M) the water dipole structure still contributes to the zeta potential, but at a higher one the zeta potential is determined by the surfactant molecules' adsorption. A special role of OH- ions is also clearly seen. Moreover, a functional relationship was found between the surface free energy of the surfactant-covered paraffin surface and the zeta potential.     

Effect of strong electrolytes on surface activity of aqueous 1,1-dimethyl-1-alkylhydrazinium chloride in aqueous solutions

The effect of electrolytes on the surface activity of aqueous anionic (1,1-dimethyl-1-alkylhydrazinium chloride homologues with the C₁₀–C₁₈ alkyl radical) and nonionic (Neonol AF 9–12) surfactants in aqueous solutions was studied.     

电解质和pH值对毒死蜱微乳液透明温度范围的影响

研究了电解质和pH值对毒死蜱微乳剂透明温度范围的影响,表面活性剂采用特殊苯乙基酚甲醛树脂聚氧乙烯醚和十二烷基苯磺酸钙(DBSCa)(质量比为3:7)复合物,质量分数75%毒死蜱二甲苯溶液为油相。研究结果表明,电解质的加入对表面活性剂作用的微乳剂透明温度范围均有显著影响,使上限温度明显下降;随阳离子电解质质量分数增加,上限温度下降;随阴离子电解质价数增加,上限温度先略增加后下降。电解质及其价数对下限温度影响均不大。弱酸性介质有利于扩大体系的透明温度范围,使上限温度达到最大值;而强酸性和强碱性介质,均使体系的上限温度下降。体系下限温度随pH值的增加缓慢升高。