Search Documents

Adsorption of Alkylammoniums in the Interlayer of Montmorillonite and its Effect on the Viscosity of Organo-Montmorillonite Gels

Sep 13, 2010

By A. M. Gaudin

IN flotation lime is used to depress pyrite. For this purpose it is preferred to caustic soda. The low cost of lime and the widespread availability largely account for this preference. However, there is some evidence1 that pyrite is more readily depressed by calcium than by sodium ions at the same pH. To measure the difference in adsorption of calcium and sodium, which is thought to lie at the basis of the differences in depressing action, radionuclides of

Jan 2, 1953

By Jacob Masliyah, Zhenghe Xu, Lujie Yan

"Understanding adsorption mechanism of polymeric organic process modifierssuch as carboxymethyl cellulose (CMC) on talc hasbeen a major challenge due to anisotropic nature of talc basal planes and edge surfaces. The main objective of this study is to investigate the adsorption of CMC on the basal planes and edge surfaces of talc.Smooth basal plane and edge surfaces of talc were prepared successfully by simple cleavage and sophisticated ultramicrotome cutting method, respectively. The prepared surfaces were characterized by atomic force microscope (AFM) imaging to be sufficiently smooth for colloidal probe force measurements using AFM. Anisotropic surface charge characteristics were determined,with the basal planes to carry a permanent negative surface charge and edge surfaces featuring a pH-dependent charge characteristic. The adsorption of CMC on talc basal plane and edge surfaces at pH 9 in KClaqueous solutions of various ionic strengths wasinvestigated by in situ AFM imaging technique. Themorphology of adsorbed CMC on talc basal planes and edge surfaces was found to be significantly different, due to different binding mechanisms involved. Interaction of CMC with the talc basal plane was found to bedominated by hydrophobic interactions while its binding with the talc edge surface was mainly through chemical complexation and hydrogen bond. The amount of CMC adsorbed on both talc basal planes and edge surfaces increased with increasing ionic strengthof solutions. The methodology developed in our study opens the door to probe polymer adsorption on anisotropic phyllosilicate surfaces, which can help us better understand the mechanism of polymer adsorption on specific mineral faces."

Jan 1, 2014

Adsorption of acrylamide based homo and copolymers on hematite was investigated as a function of phe nature of the polymer charge and functionality of the polymer. Effect of addition of sodium dodecylsulfonate and dodecylamine hydrochloride was also studied and was determined to result in an increase or decrease in the amount of polymer adsorbed depending on, the charge characteristics of the surfactant and the polymer, pH of the suspension, concentration of the various species and the order in which these species were added to the system. The surfactant adsorption under given conditions on the other hand, was found not to be affected by the presence of the polymer molecules. The data is analyzed to elucidate the mechanism of adsorption of polyacrylanide type polymers on hematite both with and without the surfactant species king present in the system.

Jan 1, 1982

By Liang Sha

In this study, adsorption of copper by chemically modified orange peel was investigated. A conspicuous change occurs in the surface morphology of the biomass due to modification, which is depicted by SEM images. Equilibrium isotherms and kinetics were obtained and the effects of various factors, including solution pH, contact time, initial metal ions concentration and temperature, were studied by batch experiments. Kinetics was found to be best-fit pseudosecond- order equations. Equilibrium was better described by Langermuir isotherms rather than Freudlich isotherms. At 25?, pH5.30, the maximum adsorption capacity was 70.67mg?g-1 . With increase of temperature, adsorption efficiency decreased. The biosorbent was suitable for repeated use for more than five cycles.

Jan 1, 2009

By Licheng Zhou

The use of aquatic plants for the removal of heavy metals from wastewater has gained high interest. In this study, batch experiments were conducted to evaluate the adsorption of copper ions in aqueous solution by P. pectinatus L. under various conditions of contact time, initial pH of the solution, metal concentration and adsorbent dosage. The results showed that the maximum adsorption amount of copper ions by P. pectinatus L. was 22.60 mg/g when the initial copper ions concentration was 98.41 mg/L at pH 4.5. The Langmuir and Freundlich models were used to describe the adsorption equilibrium of copper ions on P. pectinatus L. and the adsorption followed the Langmuir isotherm. The adsorption kinetic was well-fitted with pseudo-second-order sorption equations.

Jan 1, 2009

By N. Vorob?ev-Desyatovskii

The process of gold(I) adsorption on activated carbon (AC) from aqueous Na[Au(CN)2] and the state of the adsorbed gold cyanide complex on the adsorbent surface was investigated by photometry, XPS, XANES methods. By DFT method, quantum-chemical calculations were performed of the gold cyanide species on activated carbon surface. It was established that the binding of gold(I) with the surface of carbon involved several simultaneous processes governing the selective adsorption of gold(I) from the cyanide solutions.

Sep 1, 2012

By PDF

The adsorption of ethoxylated sulfonates and nonionics of the same ethoxylation number?on a low-ash coal has been studied. The surfactant adsorption has been investigated as a function of concentration, pH, temperature and ionic strength for three homologues. Zeta potential of coal particles and surface tension of supernatants has been concurrently determined to eludicate the orientation of sudactant molecules on the coal surface as well as the mechanism of adsorption process. The adsorption data are utilized to calculate thermodynamic parameters such as the free energy of adsorption and isoteric heats of adsorption.

Jan 1, 1988

By Catherine M. Dentan, Yosry A. Attia

The presence of finely divided carbonaceous matter, particularly graphite, in gold ores, adversely affects the adsorption - recovery of gold by activated carbon from cyanide solutions of such ores. Competitive adsorption of gold by graphite and other carbonaceous matter, is thought to be responsible for this deleterious effect In this study, adsorption of gold cyanide complex AU(CN)2- by the activated carbon used in carbon-in- pulp or carbon-in-leach processes, was compared with that by graphite which was chosen to represent the carbonaceous matter. Similar adsorption studies were made with gold chloride complex AuC14-. Correlation of adsorption with surface characteristics and thermodynamics were presented in detail, and a flowsheet for graphite-in-leach was proposed.

Jan 1, 1990

By Mustafa Yalçin, Ali Ihsan Arol

Coconut shells are the most widely used raw material for the production of activated carbon used in the gold production by cynanide leaching. There have been efforts to find alternatives to coconut shells. Shells and stones of certain fruits, have been tested. Although promising results to some extent were obtained, coconut shells remain the main source of activated carbon. Türkiye has become a country of interest in terms of gold deposits of epithermal origin. Four deposits have already been discovered and, mining and milling operations are expected to start in the near future. Explorations are underway in many other areas of high expectations. Türkiye is also rich in fruits which can be a valuable source of raw material for activated carbon production. In this study, hazelnut shells, peach and apricot stones, abundantly available locally, have been tested to determine whether they are suitable for the gold metalurgy. Parameters of carbonization and activation have been optimized. Gold loading capacity and adsorption kinetics have been studied.

Jan 1, 1995

By T. Feldmann, G. P. Demopoulos

The adsorption of gold complexes on inorganic metal oxides has been mainly discussed in geochemical literature, but it is also of interest to the hydrometallurgical industry. This is so because it could be responsible for valuable metal losses or because it could potentially serve as alternative adsorbent material to activated carbon in certain cases such as from hot and acidic process slurries. This paper constitutes an early investigation into this subject by focusing on the effectiveness of FeOOH, Fe3O4 and Al2O3 as sorbent materials. All tests were done in a batch stirred-tank reactor under atmospheric conditions with synthetic gold(III)-chloride solutions at 23°C and 80°C, in the pH range of 1.6 to 9.0. Detailed kinetic tests were performed at different pH values (3 and 6) on FeOOH and Fe3O4 with solutions having gold concentrations from 5 mg/L to 130 mg/L. The adsorption of gold was found to be best both in terms of kinetics and loading characteristics at 80°C and pH=6. This was explained by a change in Au(III)-Cl speciation from a gold(III)-chloride complex to a gold(III)-chloride-hydroxy complex. By far, magnetite (reagent grade chemical) yielded the best gold adsorption characteristics making it an interesting sorbent material for further development considering that it can be advantageously recovered from slurry streams via magnetic separation. On the other hand, the tendency of gold(III)-chloro complexes to adsorb on metal (hydro) oxides needs to be taken into account to minimize undesirable metal losses in chloride-containing leaching media.

Jan 1, 2015

By Batric Pesic

Adsorption of gold on activated carbon from gold bromide solutions was examined as a function of pH, particle size, carbon amount, initial gold bromide concentration, bromine concentration, temperature, and various cations and anions. pH did not have any effect below pH=6. Above pH=6, pH had dramatically negative effect. The adsorption results satisfied a first reaction order model. The reaction rate constant was proportional to the inverse of carbon particle radius. It was also proportional to the amount of carbon, and independent of initial gold concentration. Temperature had a very little effect at pH=l. At pH=8, the activation energy was a function of the extent of a reaction, increasing with the extent of a reaction. Cu, Fe, Ca, Mg, and Na cations and sulfate, chloride and bromide anions did not have any effect on gold adsorption. Bromine had a very negative effect on gold uptake.

Jan 1, 1991

Adsorption of guar gum was investigated on model minerals typically found in water-insoluble slimes of potash ores. The ionic strength of the adsorption mixtures was varied from distilled water to saturated NaC1 and KC1. The tests were also performed using a saturated brine. The adsorption density of guar gum on illite, dolomite, and kaolinite was found to be not only a function of total ionic strength but also of the type of electrolyte present in solution. Generally, the adsorption of the polymer on the clay minerals was higher in KC1 solutions than in NaCI, but the differences gradually disappeared when the electrolyte concentration approached saturation. The results were analyzed in terms of chaotropic (K ) or kosmotropic (Na') properties of background counter-ions and their different behaviors at the hydrated mineral-water interface. Guar gum adsorption on dolomite was related to the presence of calcium and magnesium sites on the mineral surface, and to the cis-configuration of OH groups of mannose units. Based on viscosity measurements, it was suggested that guar gum macromolecules form entanglements in NaCI solutions (and distilled water), but individual molecules exist in KC1 solutions thus creating different modes of adsorption of guar gum from concentrated NaCl and KCl solutions.

Jan 1, 2006

By Ping K. Di

A naturally aged and synthesized manganese oxide-coated granular media was found in our laboratory to have the capability of the removal of soluble Mn(H) from mine drainage by adsorption and oxidation. Mine drainage commonly also includes other heavy metal ions. Extending this principle, this paper presents the removal of heavy metals including lead, copper, cobalt, zinc and nickel in the aqueous solution by using the synthesized manganese oxide-coated granular media. It was found that the adsorption of lead, copper, cobalt, zinc and nickel on the manganese oxide-coated media follows both Langmuir and Dubinin-Radushkevich adsorption isotherms except in the concentration range less than 0.1 mmole/L. The adsorption mechanism involves the ion exchange between the heavy metal ions and synthesized manganese oxide coated on the media. The synthetic manganese oxide surface has a strong metal binding ability to the heavy metals in the order of Pb2+ > Cu2+ > Ni2+ > Zn2+ > C02+ based on the adsorption results using batch and continuous column operations. The breakthrough curves of these heavy metals showed that the synthesized media could be used effectively in the removal of these heavy metal ions in a cell or packed column. The process can simultaneously facilitate the immobilization of the heavy metals on the synthesized manganese oxide coated media. A subsequent pH adjustment dislodges the heavy metals and regenerates the synthetic media. Thus, the process accomplishes the adsorption, immobilization and concentration of the heavy metal from waste stream in one monolithic procedure.

Jan 1, 1995

By M. A. Barakat

"Adsorption of heavy metal ions specifically, Cu(II), Zn(II), Mn(II), and Cr(VI) from aqueous solution on synthetic 4A Zeolite was evaluated. The 4A zeolite was synthesized previously by dehydroxylation of low grade Kalabsha Kaolin at 800 °C, and reacted hydrothermally with 2-4 M NaOH solution at 100 °C for 2h. The adsorption capacity of the metal ions were found to be strongly dependent on pH and initial metal ion concentration. At the optimium conditions the adsorption capacity decreased in the order Cu(II) > Zn(II) > Mn(II) > Cr(VI) ions. Almost complete adsorption was achieved for both of Cu(II) and Zn(II) ions at pH > 6, while the adsorption capacity for both Mn(II) and Cr(VI) was 96, and 55.3 % at pH 11 and pH 3, respectively. The results also showed that the grain size of the 4A zeolite has a little effect on the adsorption capacity. The experimental data was compared with two adsorption isotherms, Langmuir and Freundlich isotheroms. The results showed a good agreement of the Langmuir plots with the experimental data.1. IntroductionSeveral industrial wastewater streams may contain heavy metals such as Cr, Cu, Pb, Zn, Co, Ni, Mn, etc. including the waste liquids generated by metal finishing or the mineral processing industries. Heavy metals are considered hazardous pollutants due to their toxicity, even at low concentration, and nonbiodegradability. Increasing level of heavy metals in natural water bodies poses a serious threat to all living species including humans. It is, therefore, essential to reduce the heavy metal concentration in effluents/wastewater before it is discharged into the water bodies [1]."

Jan 1, 2008

By R. F. Robertson

"Adsorption isotherms of hexyl mercaptan vapour on synthetic sphalerite, zinc sulphide and zinc oxide were de-termined with a gravimetric McBain-Baker micro balance incorporated in the B.E.T. apparatus. Isotherms are given for hexyl mercaptan on synthetic sphalerite at 25°C, 0.5°C and 50°C; on zinc sulphide at 25°C and 1.5°C; and on zinc oxide at 25°C. All these isotherms are sigmoidal, with a definite change in slope at or close to the mono-layer. The amount of mercaptan adsorbed below the monolayer increases almost linearly with relative pressure to P/P0 = 0.8.Above this value, the amount adsorbed increases very rapidly with relative pressure. Hysteresis loops appear in the isotherms for all adsorption-desorption cycles. These loops are completely reversible. It is not possible to desorb the mercaptan monolayer from any of the adsorbents, even at elevated temperatures."

Jan 1, 1966

By S. Vivek

An Atomic force microscope (AFM) was used to measure the surface forces between hydrophobic silica surfaces. The measurements were conducted in the presence and absence of Cu(II)species in solution to study the effects of the cation adsorption on the hydrophobic force. The results obtained in the absence of the Cu (II)species showed that the hydrophobic force does not change with pH, while the electrostatic repulsive force changes substantially with pH. In the presence of the Cu(II) species, the hydrophobic force begins to decrease at a pH where Cu2+ions are hydrolyzed, indicating that the first hydrolysis product (i.e., CuOH+ions) are the species adsorbing on the surface of the hydrophobic silica. The results of the surface force measurements were used to develop a model for the adsorption of the hydrolysis product of Cu(II) species on the hydrophobic silica.

Jan 1, 2003

By Ying Qin, Shujing Zhu

The characterization of adsorption of natural and composite bentonite in lead aqueous solution has been studied. The results showed that adsorption of both natural and composite bentonites strongly depended on the pH values of the solution. At lower pH values, the mechanisms that govern the adsorption of bentonites were dissolution of crystal structure and competition between the metal ions and the H+. To composite bentonite, the lead ion removal capacity was close to 250 mg/g. At higher pH values, formation of lead hydroxyl species might lead to either participation to the adsorption or precipitation onto the bentonites. Hence, a rapid increase in the equilibrium removal capacity of lead was obtained when pH > 7.0. An increase in the initial lead ion concentration led to the increase in the equilibrium adsorption capacity increased to a certain degree; and then, a plateau was obtained at higher concentrations. As a result, the adsorption performance of composite bentonite was better than the natural bentonite in both physical and chemical changes. The data fitted well with both Langmuir and Freundlich isotherms.

Mar 1, 2017

By H. Z. Liu, J. M. Zhao, F. C. Wang

"Novel silicate-alginate composite beads containing 2-ethylhexyl phosphonic acid mono-2- ethylhexyl ester (P507) were synthesized and applied for the adsorption of Nd3+ from aqueous solutions. The adsorption amount of Nd3+ has been increased owing to the introduction of P507. The effect of equilibrium pH (pHe), the kinetic and isotherm experiments were investigated. The adsorption reaches equilibrium at 9 h and the maximum uptake capacity is up to 195.4 mg/(g dry adsorbent). The Langmuir isotherm equations are used to describe the adsorption process. Complete desorption can be realized with 0.2 M HCl within 20 min. INTRODUCTIONRare earth elements (REEs) have found various applications in different domains, such as metallurgy industry, ceramic industry, nuclear fuel control, photo-electro-magnetic functional materials owing to their unique properties. Neodymium (Nd), as a representative of all of the most valuable REEs, is widely used as catalysts, laser crystals, capacitors, rubber additives, Nd-Fe-B magnets, hydrogen storage and so on. Thus, the separation and purification of neodymium is significant. Unfortunately, Nd always coexists with other REEs and selective separation of the individual Nd from the REEs mixtures is still extremely difficult owing to their strictly similar atomic structures and chemical properties.Liquid-liquid extraction (LLE) and solid-liquid adsorption (SLA) are the most widely adopted techniques for the separation of REEs in the hydrometallurgical fields. The LLE process is well suited for large-scale continuous operation because of its inherent high capacity and fast kinetics. Nowadays, as a commercial extractant, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) has been extensively studied for extraction and separation of REEs since it has considerably good extractability and high separation efficiency (Xu et al., 1992). SLA is one of the effective and green separation methods with some prominent advantages, such as easy regeneration of adsorbents, small footprint size, less industrial wastes, higher enrichment factors and column efficiency,rapid solid–liquid separation without emulsion and so on. Hence, the introduction of extractants with excellent performance into adsorbents will integrate the advantages of LLE and SLA (Lee et al., 2009)."

Jan 1, 2012

By P. Somasundaran

Adsorption of a nonionic polyacrylamide (PAM), an anionic polyacrylamide with sulfonate functional groups (PAMS), and a cationic polyacrylamide with amine functional groups (PAMD), on hematite was investigated as a function of different solution conditions. Adsorption results indicate that the major mechanisms of adsorption of polyacrylamides on hematite is through hydrogen bonding, with electrostatic forces playing a secondary role. All the polymers exhibited irreversibility of adsorption upon dilution. Also, entropic effects were determined to be important in adsorption. Surface chemical properties of hematite and solution chemistry of the polyacrylamides are considered to explain the polymer adsorption behavior on hematite.

Jan 1, 1985