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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 G. M. Li

It is shown that seriously preoxidized arsenopyrite can adsorb a large amount of copper ions as unoxidized one, but without, release of corresponding amount of Fe ions; seriously preoxidized pyrite cannot adsorb copper ions, but with release of a large amount of Fe ions. However, if the minerals are rapidly oxidized with potassium permanganate solution, both arsenopyrite and especially pyrite can adsorb a large amount of copper ions, but still without release of corresponding amount, of Fe ions. Cu adsorption (if there is any) on both oxidized arsenopyrite and pyrite is not based on the Cu-Fe exchange mechanism.

Jan 1, 1991

By Sadan Kelebek, S. O. Fekete, Gerhard W. Heinrich, Peter F. Wells

"For many years, rejection of pyrrhotite at the milling stage has been a viable method for sulphur dioxide abatement. Pyrrhotite rejection options have included the use of selective pyrrhotite depressants in flotation; a depressant which has recently come into use is diethylenetriamine (DETA). This reagent has been the subject of recent research and development efforts in the processing of nickel-copper sulphide ores.In the present study, adsorption trends for DETA have been monitored under the dynamic conditions of flotation using a spectrophotometric method which has been adopted for this purpose at Falconbridge Limited. The results indicate that the adsorption of DETA is quite fast and in the majority of cases, accounts for the disappearance of 75-95 % of this reagent from pulp's liquid phase. The adsorption decreases linearly with an increase in the DET A dosage from 100 git to 600 git. The tailings produced in flotation tests were subjected to washing with deionized water at 60 °C to examine the desorption of DET A. These results indicate that the amount desorbed increases with increasing DETA dosage used during flotation but is less than 7 per cent of that adsorbed. It was found that adsorption of DETA alone, even at relatively high levels, does not always cause depression of pyrrhotite. A new combination of reagents identified in the metallurgical laboratories of Falconbridge Limited utilizes sulphur dioxide with DETA. These reagents together are capable of efficient depression of pyrrhotite on a consistent basis."

Jan 1, 1995

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 A. M. Gaudin, J. G. Morrow

FLOTATION requires the existence of a definite contact angle. This contact angle, the surface tension of the solution, and adsorption at the solid- fluid interface are quantitatively related. Adsorption of dodecylammonium acetate on hematite was measured for a wide range of concentrations of reagent in solution. Similar measurements for quartz have already been made.1 Contact angle measurements were then made on polished surfaces of hematite and of quartz immersed in aqueous dodecylammonium acetate solutions, and a functional relationship was sought between adsorption density at the mineral-solution interface and the contact angle. Finally, the surface tension of the aqueous amine acetate solutions was measured. These data were combined to give an evaluation of the work of adhesion for the three-phase system.

Jan 12, 1954

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 A. M. Gaudin, Olav Mellgren, P. L. De Bruyn

In commonly used to prepare the surface of the mineral to be floated so that attachment to air takes place. The quantity of agent required to make the mineral hydrophobic is usually very small, of the order of 0.1 to 0.25 lb per ton of mineral. Details of the mechanism of pyrite collection are for the most part unsettled. Adsorption of collector has long been believed to involve an ion exchange mechanism as demonstrated for galena' and for chalcocite. In the work on chalcocite it was also demonstrated that a film of xanthate radicals unleachable in solvents that dissolve alkali xanthates, copper xanthate, or dixanthogen was formed at the surface of the mineral. The unleachable product increased with increasing addition of xanthate up to a maximum corresponding to an oriented monolayer of xanthate radicals. Pyrite is extremely floatable with xanthate if its surface is fresh,,' but the floatability decreases rapidly as oxide coatings increase in abundance. Pyrite shows zero contact angle when in contact with ethyl xanthate solution at pH higher than about 10.5; at neutrality. a contact angle of 60° is obtained at a reagent concentration of 25 mg per liter. Alkali sulfides and cyanides are pyrite depressants.

Jan 1, 1956

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 K. N. Han

The adsorption of gold onto activated carbon in iodide solutions was studied. The adsorption rates were determined as a function of temperature, salt concentration and pH, as well as activated carbon concentration. A kinetic model was developed for the adsorption. The adsorption rate was believed to be controlled by a combined mechanism of film diffusion and pore diffusion with the film diffusion having the most significant effect. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1995

The adsorption of gold onto activated carbon in iodide solutions has been studied. The adsorption rates were determined as a function of temperature, salt concentration and pH as well as activated carbon concentration. A kinetic model was also developed for the adsorption. The adsorption rate was believed to be controlled by a mixed mechanism of film diffusion and pore diffusion, but the film diffusion had a major contribution to the overall rate. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1993

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 Gjergj Dodbiba, Toyohisa Fujita, Takahiro Kikuchi, I-Chen Wu

"In order to separate molybdenum (Mo) from the high-level radioactive liquid waste (HLLW), Pb-Fe based adsorbents were synthesized. The adsorbents were precipitated by adding sodium hydroxide in mixture of 1 mol/L lead nitrate and 1 mol/L ferric nitrate aqueous solutions. Each precipitate was then filtered, dried and ground to obtain a fine powder, which has been used as an adsorbent. Two main parameters were considered when synthesizing the adsorbents, i.e. the pH value at precipitation of adsorbent precursor and the calcination temperature of Pb-Fe based adsorbent. Moreover, the structures of the synthesized adsorbents were investigated by means of an X-ray diffractometer.The experimental results indicated that the calcination temperature of the Pb-Fe based adsorbent has a great influence on adsorption capacity of the adsorbent for Mo. It was found that when the Pb-Fe based adsorbent was calcinated at 500 oC, the sorbed concentration of Mo was the highest.1. IntroductionThe high-level radioactive liquid waste (HLLW), arising from the reprocessing of nuclear fuel are generally immobilized in an alkali borosilicate glass matrix. Broadly speaking, alkali borosilicate glasses are the matrix of choice for the immobilization of the HLLW, since they permit vitrification of waste stream of variable composition, [1]. Within this frame, the incorporation of molybdenum (Mo) is of particular interest in the vitrification of HLLW. Molybdenum is know to have a low solubility in borosilicate glass compositions and its presence in excess results in the phase separation of a complex yellow molten salt during vitrification, [1]. The formation of so-called “yellow phase” material during the vitrification process is undesirable since it leads to the accelerated corrosion of the inconel crucible liners. Furthermore, the “yellow phase”, which is reported to contain also other fission products, is soluble in aqueous solution providing a potential route for the leaching of radionuclides from the vitrified waste, should it come into contact with water, [1]."

Jan 1, 2008