ADSORPTION AND CO-ADSORPTION OF PEO-PPO-PEO BLOCK COPOLYMERS AND SURFACTANTS AND THEIR INFLUENCE ON ZETA POTENTIAL OF MAGNESITE AND DOLOMITE

Abstract. The influence of adsorption and co-adsorption of PEO-PPO-PEO triblock copolymers (Pluronics) as well as surfactants on the zeta potential of magnesite and dolomite aqueous suspension are addressed here. Four Pluronics of various molecular weight were used in these studies. They have been mixed with cationic (CTAB) or anionic (SDS) surfactants. The adsorption isotherms of copolymers and copolymer-surfactant mixture onto magnesite and dolomite have been determined. The adsorbed amount of Pluronics increases with the increasing concentration and reaches plateau. An increase in the adsorbed amounts of both cationic and anionic surfactants onto the mineral surfaces (magnesite and dolomite) has been observed in the presence of Pluronic copolymers. A positive nature of zeta potential was observed in the presence of cationic surfactant, except magnesite without or with a low CTAB concentration. However, an attendant copolymer causes a decrease of zeta potential due to the deformation of an electrical double layer, comparing the presence of an individual cationic surfactant. The adsorbed non-ionic Pluronic layer partially screens the surface charge of mineral particles, and thus, reduces the zeta potential. On the other hand, the adsorption of anionic surfactant and copolymer caused a decrease in the negative value of the zeta potential of both investigated minerals due to increased SDS adsorption. The viscosity measurements were also performed to determine the thickness of adsorbed layer

Surfactin as a Green Agent Controlling the Growth of Porous Calcite Microstructures

This study presents a new, simple way to obtain mesoporous calcite structures via a green method using an eco-friendly surface-active compound, surfactin, as a controlling agent. The effects of synthesis time and surfactin concentration were investigated. The obtained structures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) coupled with gas mass spectrometry (QMS) analysis. The experimental data showed that surfactin molecules significantly changed the morphology of the calcite crystals, roughening and deforming the surface and creating a greater specific surface area, even at low biosurfactant concentrations (10 ppm). The size of the crystals was reduced, and the zeta potential value of calcium carbonate was more negative when more biosurfactant was added. The XRD data revealed that the biomolecules were incorporated into the crystals and slowed the transformation of vaterite into calcite. It has been shown that as long as vaterite is present in the medium, the calcite surface will be less deformed. The strong influence of surfactin molecules on the crystal growth of calcium carbonate was due to the interaction of surfactin molecules with free calcium ions in the solution as well as the biomolecules adsorption at the formed crystal surface. The role of micelles in crystal growth was examined, and the mechanism of mesoporous calcium carbonate formation was presented

Radial Basis Function Neural Network based on Growing Neural Gas Network applied for evaluation of oil agglomeration process efficiency

In this study, the neural model for modeling of oil agglomeration of dolomite in the presence of anionic and cationic surfactants (sodium oleate and dodecylammonium hydrochloride) was implemented. The effect of surfactants concentration, oil dosage, time of mixing, pH, and mixing speed of the impeller in the process recovery were investigated using Radial Basis Function Neural Network (RBFNN). A significant problem in this modeling, was the selection of the structure of the neural network. In algorithms based on the RBFNN, the issue mentioned relates to the number of nodes in the determination of the hidden layer. Also, the distribution of functions in data space is significant. In the proposed solution, at this stage of the neural model design, the Growing Neural Gas Network (GNGN) was implemented. Such a procedure introduced automation of the calculation process. The centers were obtained from the GNGN and the structure (number of radial neurons) can be approximated based on a simple searching algorithm. The idea of the data calculations was implemented as an original algorithm that can be easily transferred to Matlab, Python, or Octave software. The values predicted from the neural networks model were in good agreement with the experimental data. Thus, the RBFNN-GNGN model used in this study, can be employed as a reliable and accurate method to predict, and in the future to optimize the performance of oil agglomeration process

Adsorption of Silver Nanoparticles on Glass Beads Surface

Colloidal silver is widely used owing to its specific properties, which enable it to be applied in various fields. In this work, adsorption of commercially available silver nanoparticles (AgNPs; NanoSilver PVP 1000) on glass beads was investigated. The glass microspheres (70–110 μm) were used as model particles. The adsorption of AgNPs on the glass beads surface was investigated in terms of adsorbent dosage. The adsorption isotherm was determined with the adsorbent dosage of 100 g/l and the AgNPs in range 100–1000 mg/l. It was found that adsorption isotherm data best fitted the Langmuir model. Kinetics of AgNPs adsorption onto glass beads followed a pseudo-second-order model. The interaction between glass microspheres surface and polyvinylpyrrolidone (PVP)-coated AgNPs is due to hydrogen bonding with oxygen of carbonyl groups of PVP and silanol groups on the glass surface

Protein-Mediated Precipitation of Calcium Carbonate

Calcium carbonate is an important component in exoskeletons of many organisms. The synthesis of calcium carbonate was performed by mixing dimethyl carbonate and an aqueous solution of calcium chloride dihydrate. The precipitation product was characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) measurements. In addition, the turbidity of the reaction solution was acquired to monitor the kinetics of the calcium carbonate structure’s growth in the investigated system. In this study, samples of CaCO3 particles obtained with individual proteins, such as ovalbumin, lysozyme, and a mixture of the proteins, were characterized and compared with a control sample, i.e., synthesized without proteins. The obtained data indicated that the addition of ovalbumin to the reaction changed the morphology of crystals from rhombohedral to ‘stack-like’ structures. Lysozyme, however, did not affect the morphology of calcium carbonate, yet the presence of the protein mixture led to the creation of more complex composites in which the calcium carbonate crystals were constructed in protein matrices formed by the ovalbumin-lysozyme interaction. It was also observed that in the protein mixture, ovalbumin has a major influence on the CaCO3 formation through a strong interaction with calcium ions, which leads to the coalescence and creation of a steric barrier reducing particle growth. The authors proposed a mechanism of calcium carbonate grain growth in the presence of both proteins, taking into account the interaction of calcium ions with the protein

Influence of Zwitterionic CAPB on Flocculation of the Aqueous Cationic Guar Gum/Glauconite Suspensions at Various pH

The influence of the pseudoamphoteric zwitterionic surfactant cocamidopropylbetaine (CAPB) on the stabilizing flocculating properties of the aqueous suspensions of glauconite (GT) with cationic guar gum (CGG) at various pH values was investigated. The following techniques were used: turbidimetry, UV-VIS spectrophotometry, tensiometry, electrophoretic mobility measurements, SEM, CHN, XRD, and FT-IR. It was established that CGG is an effective glauconite flocculant. Moreover, the most probable mechanism that is responsible for flocculation is bridge flocculation resulting from polymer adsorption on the glauconite surface. The adsorption process is caused by electrostatic interactions between the negatively charged glauconite surface and the positively charged polymer. The amount of CGG adsorption increases with the increase of the pH, which was confirmed by the adsorption and zeta potential measurements. The addition of CAPB increases the amount of the polymer adsorption due to the formation of intermolecular polymer–surfactant complexes; however, it reduces flocculation effectiveness

Rhamnolipids as Effective Green Agents in the Destabilisation of Dolomite Suspension

In this paper, we describe an application of mono- and dirhamnolipid homologue mixtures of a biosurfactant as a green agent for destabilisation of a dolomite suspension. Properties of the biosurfactant solution were characterised using surface tension and aggregate measurements to prove aggregation of rhamnolipids at concentrations much lower than the critical micelle concentration. Based on this information, the adsorption process of biosurfactant molecules on the surface of the carbonate mineral dolomite was investigated, and the adsorption mechanism was proposed. The stability of the dolomite suspension after rhamnolipid adsorption was investigated by turbidimetry. The critical concentration of rhamnolipid at which destabilisation of the suspension occurred most effectively was found to be 50 mg·dm−3. By analysing backscattering profiles, solid-phase migration velocities were calculated. With different amounts of biomolecules, this parameter can be modified from 6.66 to 20.29 mm·h−1. Our study indicates that the dolomite suspension is destabilised by hydrophobic coagulation, which was proved by examining the wetting angle of the mineral surface using the captive bubble technique. The relatively low amount of biosurfactant used to destabilise the system indicates the potential application of this technology for water treatment or modification of the hydrophobicity of mineral surfaces in mineral engineering

Removal of As(V) using liquid-phase polymer-based retention (LPR) technique with regenerated cellulose membrane as a filter

WOS: 000322156300009In this study, regenerated cellulose membrane was used as a filter in liquid-phase polymer-based retention technique. The poly(4-vinyl-1-methylpyridinium bromide), P(BrVMP), was used as extracting reagent of As(V). The role of pH, polymer:As(V) molar ratio, and influence of regenerated cellulose membrane were investigated by washing method. It was observed that the efficient retention was obtained at pH 9 with 20:1 polymer:As molar ratio and it was about 100 % at Z = 10 for P(BrVMP). Experimental data showed that the regenerated cellulose membrane, compared to poly(ethersulfone) membrane, has a capacity to interact with As(V). The maximum retention capacity of P(BrVMP) was determined by enrichment method, and then, using alternately washing and enrichment methods, the charge-discharge process and recovery of P(BrVMP) were performed.7FP-MC Actions Grant so-called CHILTURPOL2 (PIRSES-GA Project) [269153]; FONDECYTComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1110079, 3120048]; PIA [Anillo ACT 130]The authors thank to 7FP-MC Actions Grant so-called CHILTURPOL2 (PIRSES-GA-2009 Project, Grant Number: 269153) for a fellowship to Dr. A. Bastrzyk to do research at University of Concepcion, Chile. The authors are also grateful for Grants FONDECYT (No 1110079) and PIA (Grant Anillo ACT 130) for financial support. Julio Sanchez thanks also FONDECYT (postdoctoral Grant No 3120048) and CIPA