scholarly journals Study on the Oxidative Leaching of Uranium from the Lignite in the CO32-/HCO3- System

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Y. Ning ◽  
Y. Li ◽  
Y. Zhang ◽  
P. Tang
Keyword(s):  
Yunnan Province ◽  
Reaction Model ◽  
Second Order Reaction ◽  
Liquid Ratio ◽  
Uranium Leaching ◽  
Pseudo Second Order ◽  
Oxidative Leaching ◽  
Solid Liquid ◽  
Leaching Efficiency ◽  
Alcoholic Hydroxyl

Na2CO3/NaHCO3 mixtures with different oxidants were used to leach uranium in the lignite which was obtained from Lincang, Yunnan province. The experimental results showed that the optimal solid/liquid ratio and CO32-/HCO3- ratio for uranium leaching were 1 : 20 (g/mL) and 2 : 1, respectively. With the increase of carbon concentration from 0.1 mol/L to 1.1 mol/L, the leaching efficiency of uranium increased from 14.64% to 42.39% after 6 h leaching. The oxidants could significantly enhance the uranium leaching efficiency, which was up to 72.23% by injecting O2 at 1.5 L/min after 12 h leaching. The oxidative leaching process of uranium from the lignite was better fitted to the pseudo-second-order reaction model. The sequential extraction results illustrated that the oxidants could effectively enhance the leaching of organic matter bound uranium in the lignite, which was decreased from 76.86 mg/kg to 9.00 mg/kg by injecting O2. The infrared spectrum analysis demonstrated that the corresponding transmittance at about 3197 cm−1 was prominently reduced after the oxidative leaching, which intimated that the phenolic and alcoholic hydroxyl might be the main functional groups combined with uranium in the lignite.

Adsorption of copper ion on magnetite-immobilised chitin

2007 ◽  
Vol 56 (7) ◽  
pp. 135-143 ◽  
Author(s):  
K.S. Wong ◽  
K.H. Wong ◽  
S. Ng ◽  
W.K. Chung ◽  
P.K. Wong
Keyword(s):  
Exchange Resin ◽  
Cation Exchange Resin ◽  
Standard Free Energy ◽  
Copper Ion ◽  
Reaction Model ◽  
Second Order Reaction ◽  
Batch Mode ◽  
Adsorption Capacities ◽  
Endothermic Process ◽  
Pseudo Second Order

The adsorption of Cu2 +  from aqueous solution by magnetite-immobilised chitin (MC) was studied in batch mode. Two conventional adsorbents, cation exchange resin (CER) and activated carbon (AC) were used for the comparison. The physicochemical parameters including pH, concentration of adsorbent, temperature and initial Cu2 +  concentration were optimised. Under the optimised conditions, the removal efficiencies of Cu2 +  for MC, CER and AC were 91.67, 93.36 and 89.16%, respectively. In addition, the removal capacities of Cu2 +  for MC, CER and AC were 56.71, 74.84 and 6.55 mg/g, respectively. The adsorption isotherm studies indicated that the adsorptive behaviour of Cu2 +  on three adsorbents could be well described by the Langmuir model. The maximum adsorption capacities (qmax) for MC, CER and AC were 53.19, 89.29 and 5.82 mg/g, respectively. The applicability of the kinetic model has been investigated for MC. Experimental results indicated that a pseudo-second-order reaction model provided the best description of the data with a correlation coefficient 0.999 for different initial Cu2 +  concentrations. The rate constants were also determined. Various thermodynamic parameters such as standard free energy (ΔG0), enthalpy (ΔH0) and entropy (ΔS0) were calculated for predicting the adsorption nature of MC. The results indicated that this system was a spontaneous and endothermic process.

scholarly journals Performance of natural and modified smectite: kinetic and thermodynamics involving arsenic (V) adsorption

Cerâmica ◽  
2010 ◽  
Vol 56 (337) ◽  
pp. 49-56 ◽  
Author(s):  
D. L Guerra ◽  
C Airoldi ◽  
R. R Viana
Keyword(s):  
Room Temperature ◽  
Adsorption Process ◽  
Textural Analysis ◽  
Order Reaction ◽  
29Si Mas Nmr ◽  
Second Order Reaction ◽  
Calorimetric Titration ◽  
Pseudo Second Order ◽  
Solid Liquid Interface ◽  
Solid Liquid

A natural smectite sample has been modified by organofunctionalization process using synthetic route involved the reaction of 2-mercaptopyrimidine with 3-chloropropyltriethoxysilane. The resulting material (S MPY) was characterized by SEM, FTIR, textural analysis and 29Si MAS-NMR. The ability of this material to removed As (V) from aqueous solution was followed by series of adsorption isotherms adjusted to the Langmuir equation at room temperature and pH 2.0. The kinetic parameters analyzed by Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k2 in the 4.9 to 14.0 mmol-1 min-1 range for S MPY. The adsorption process was exothermic (ΔintH = -4.09 to -5.79 kJ.mol-1) accompanied by increase in entropy (ΔintS = 41.29 to 61.80 JK-1.mol-1) and Gibbs energy (ΔintG = -22.34 to -24.19 kJmol-1). The energetic effect caused by arsenic cation adsorption was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.

scholarly journals Adsorption of As(V) and As(III) from aqueous solution by lepidocrocite (γ-FeOOH) nanoparticle

2016 ◽  
Vol 19 (4) ◽  
pp. 270-281
Author(s):  
Trung Dinh Nguyen ◽  
Phuong Dong Truong
Keyword(s):  
Adsorption Equilibrium ◽  
Reaction Model ◽  
Precipitation Method ◽  
Second Order Reaction ◽  
High Adsorption ◽  
Freundlich Isotherms ◽  
Adsorption Capacities ◽  
Adsorption Data ◽  
Pseudo Second Order ◽  
Co Precipitation

γ-FeOOH nanorods an adsorbent for As(V) and As(III) removal was prepared by a chemical co-precipitation method. The maximum adsorption capacities at pH6 for As(V) and As(III) were 63.75 and 88.99 mg/g, respectively, higher than those of Fe2O3, Fe3O4... The adsorption data accorded with Freundlich isotherms. At the study pH, for arsen, the adsorption equilibrium was gained after 90 min. Kinetic data fitted well to the pseudo-second-order reaction model. The adsorption of γ-FeOOH for As (V) and As(III) could be competed by some other ion such as sulfate, ammonium and chloride. The high adsorption capability and good performance on other aspects make the γ-FeOOH nanorod a promissing adsorbent for the removal of As (V) and As(III) from the groundwater.

The Solubility of Phosphogypsum and Recovery of Heavy and Radioactive Elements

2020 ◽  
Vol 38 (10A) ◽  
pp. 1470-1480
Author(s):  
Waleed T. Rashid ◽  
Israa A. Alkadir ◽  
Moayyed G. Jalhoom
Keyword(s):  
High Mobility ◽  
Major Elements ◽  
Radioactive Elements ◽  
Liquid Ratio ◽  
Phosphate Fertilizers ◽  
Negative Effect ◽  
Temperature Ranges ◽  
Solid Liquid ◽  
Positive Effect ◽  
Leaching Efficiency

The essential purpose of this paper is to illustrate and inspect the leaching characteristics of Iraqi Phosphogypsum (PG). The paper presents the results of the dissolution characteristics of heavy and radioactive elements from PG, which is a by-product result from the industry of phosphate fertilizers. Leachability of heavy and radioactive elements in deionized water that has been inspected under various states of leaching, including solid/liquid ratio (10, 20 and 50 /1g/L) and temperatures (25, 45 and 85 °C), with constant other parameters such as string speed (300 rpm) and contact time (60 minutes). For the most analysis elements, the progressive release of the metals, in addition to the major elements reflects high mobility.  The mobility of trace metals in PG has been generally classified into three main degrees: (1) high mobility elements such as Pb, Zn, Mn, and Cr; (2) moderate mobility elements such as Sr, V, Ba,Y,Hg, K and Ni; and (3)l ow mobility elements like Ca,Cu,Fe, and Ag. The maximum concentrations of the most of the metals were attained from a leaching state of 10/1g/L. Regarding temperature, the experimental results revealed that the PG solubility to leaching out elements increases noticeably as the applied temperature ranges from 25 to 45 °C; after this degree, the leaching efficiency decreases. Chloride had a positive and negative effect on the solubility of phosphorus. Calcium chloride had an adverse effect on solubility and observed reduced solubility with increased chloride. While the positive effect of sodium and magnesium chloride was observed, the solubility...

scholarly journals Efficient removal of tetracycline with KOH-activated graphene from aqueous solution

2017 ◽  
Vol 4 (11) ◽  
pp. 170731 ◽  
Author(s):  
Jie Ma ◽  
Yiran Sun ◽  
Fei Yu
Keyword(s):  
Ionic Strength ◽  
High Specific Surface Area ◽  
Order Kinetic ◽  
Liquid Ratio ◽  
Promising Alternative ◽  
Order Kinetic Model ◽  
Langmuir Isotherm Model ◽  
Pseudo Second Order ◽  
Solid Liquid ◽  
Coexisting Ions

Activated graphene absorbents with high specific surface area (SSA) were prepared by an easy KOH-activated method, and were applied in absorbing antibiotics, such as tetracycline (TC). After activation, many micropores were introduced to graphene oxide sheets, leading to higher SSA and many new oxygen-containing functional groups, which gave KOH-activated graphene excellent adsorption capacity (approx. 532.59 mg g −1 ) of TC. Further study on the adsorption mechanism showed that the Langmuir isotherm model and the pseudo-second-order kinetic model fitted with experiment data. To further understand the adsorption process, the effects of solid–liquid ratio, pH, ionic strength and coexisting ions were also investigated. The results revealed that, compared with pH and ionic strength, solid–liquid ratio and coexisting ions (Cu 2+ , CrO 4 2− ) had more significant influence over the adsorption performance. The findings provide guidance for application of KOH-activated graphene as a promising alternative adsorbent for antibiotics removal from aqueous solutions.

scholarly journals A hydrometallurgical process for the recovery of cerium from Khuren khad ore

2019 ◽  
pp. 32-37
Author(s):  
Sandagdorj N ◽  
Enerel B ◽  
Ching-Hwa Lee ◽  
Gankhuyag E ◽  
Terbish N
Keyword(s):  
Recovery Efficiency ◽  
Hydrometallurgical Process ◽  
Liquid Ratio ◽  
Precipitation Product ◽  
Solid Liquid ◽  
Leaching Efficiency

This study presents the recovery of cerium (Ce) from Khuren Khad ore by using the hydrometallurgical process. Several methods of leaching and precipitation were employed to investigate the recovery efficiency of Ce from the ore. According to the result, it is 4.8% of Ce contained in this ore sample. The best result of this study reveals that 100% Ce leaching efficiency can be obtained under leaching conditions of 6N HCl at a temperature of 70° C and 5g/50mL solid/liquid ratio and 3h. Further, 99.60% precipitation recovery of Ce was achieved with NaHCO3 at an interval of 24 hours. After leaching and precipitation, the concentration of Ce was enriched from 4.8% of Khuren Khad ore to 33.09% of precipitation product.

scholarly journals Removal of methylene blue by biosorption onto Stipa tenacissima L. (Alfa) plants: Kinetics, equilibrium and thermodynamic studies

2021 ◽  
pp. 33-44
Author(s):  
Samir Ladjali ◽  
Nadjib Dahdouh ◽  
Samira Amokrane ◽  
El Mekatel ◽  
Djamel Nibou
Keyword(s):  
Methylene Blue ◽  
Contact Time ◽  
Blue Dye ◽  
Order Kinetic ◽  
Liquid Ratio ◽  
Stipa Tenacissima ◽  
Equilibrium Data ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Solid Liquid

This study examines the ability of Stipa tenacissima L. (Alfa) to biosorb the Methylene Blue dye. Biosorption tests were performed in aqueous solution based on certain essential parameters such as solution?s pH (2-12), solid/liquid ratio (1-6 g/L), initial dye concentration (25-125 mg/L) and contact time (0-300 min). The Langmuir, Freundlich, Temkin and Elovich models were applied. It was found that the equilibrium data could be fitted to the Langmuir isotherm for MB biosorption with a maximum capacity qmax 55, 95 mg/g. The kinetic study shows that the experimental data correspond to the pseudo-second order kinetic model. The negative Gibbs values free energy ?G? reveal the spontaneity of MB biosorption at the surface of Stipa tenacissima L. The positive value of ?H? reveals the endothermic nature of the process.

Adsorption of In3+ from Aqueous Solutions by Persimmon Tannins-Immobilized Collagen Fiber

2013 ◽  
Vol 788 ◽  
pp. 114-118 ◽  
Author(s):  
Feng Lei Liu ◽  
Zhong Min Wang ◽  
Huai Gang Zhang ◽  
Gui Yin Li ◽  
Huai Ying Zhou
Keyword(s):  
Adsorption Capacity ◽  
Collagen Fiber ◽  
Low Cost ◽  
Initial Solution ◽  
Liquid Ratio ◽  
Solution Ph ◽  
Freundlich Model ◽  
Treatment Conditions ◽  
Pseudo Second Order ◽  
Solid Liquid

In the present work, a novel adsorbent to effectively adsorbed In3+ from an aqueous solution has been prepared by immobilizing persimmon tannin (PT) on collagen fiber. The adsorption capacities of In3+ on the immobilized PT were evaluated under various treatment conditions including the initial solution pH, solid-liquid ratio and temperature. The results showed that the effect of initial solution pH and solid-liquid ratio on the adsorption capacity were remarkable, while the influence of temperature was insignificant. The adsorption capacity reached 420 mg/g at 303 K and pH 5.0 when the initial concentration of In3+ was 100 mg/L and solid-liquid ratio was 0.2. The adsorption isothermal and kinetic data fitted best to the Freundlich model and the pseudo-second-order model, respectively.All these results indicated that adsorbent adsorbed efficiently and could be used as a low-cost alternative for the adsorption of In3+ in wastewater treatment.

Extraction of Tungsten and Vanadium from the Spent SCR Catalyst by High Pressure Alkaline Leaching Method

2018 ◽  
Vol 913 ◽  
pp. 954-960 ◽  
Author(s):  
Jia Peng Chen ◽  
Li Wen Ma ◽  
Ming Xing Cao ◽  
Xiao Li Xi
Keyword(s):  
High Pressure ◽  
Catalytic Reduction ◽  
Sodium Hydroxide Solution ◽  
Liquid Ratio ◽  
Alkaline Leaching ◽  
Scr Catalyst ◽  
Solid Ratio ◽  
Alkali Leaching ◽  
Solid Liquid ◽  
Leaching Efficiency

Tungsten and vanadium are efficiently extracted from honeycomb-type spent selective catalytic reduction (SCR) catalyst by using a high pressure alkali leaching method. Theoretical thermodynamics calculation indicates that WO3and V2O5are soluble in sodium hydroxide solution, proving that the extraction of Wand V from the spent SCR catalyst by high pressure alkaline leaching is feasible. The effects of NaOH concentration, leaching temperature and time, liquid-solid ratio and stirring speed on leaching efficiency of W and V are systematically investigated. The leaching efficiency of W and V is 94.3% and 91.2%, respectively, under the optimal conditions: the NaOH concentration of 2mol/L, the leaching temperature 463.5 K, the reaction time 3 h, solid-liquid ratio 0.1 g/ml, the stirring speed of 400 r/min. The TiO2residue is in anatase crystalline phase.

scholarly journals Preparation and Characterization of the Sulfur-Impregnated Natural Zeolite Clinoptilolite for Hg(II) Removal from Aqueous Solutions

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 217
Author(s):  
Marin Ugrina ◽  
Martin Gaberšek ◽  
Aleksandra Daković ◽  
Ivona Nuić
Keyword(s):  
Chemical Modification ◽  
Aqueous Solutions ◽  
Specific Surface ◽  
Surface Area ◽  
Natural Zeolite ◽  
Contact Time ◽  
Liquid Ratio ◽  
X Ray ◽  
Solid Liquid

Sulfur-impregnated zeolite has been obtained from the natural zeolite clinoptilolite by chemical modification with Na2S at 150 °C. The purpose of zeolite impregnation was to enhance the sorption of Hg(II) from aqueous solutions. Chemical analysis, acid and basic properties determined by Bohem’s method, chemical behavior at different pHo values, zeta potential, cation-exchange capacity (CEC), specific surface area, X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetry with derivative thermogravimetry (TG-DTG) were used for detailed comparative mineralogical and physico-chemical characterization of natural and sulfur-impregnated zeolites. Results revealed that the surface of the natural zeolite was successfully impregnated with sulfur species in the form of FeS and CaS. Chemical modification caused an increase in basicity and the net negative surface charge due to an increase in oxygen-containing functional groups as well as a decrease in specific surface area and crystallinity due to the formation of sulfur-containing clusters at the zeolite surface. The sorption of Hg(II) species onto the sulfur-impregnated zeolite was affected by the pH, solid/liquid ratio, initial Hg(II) concentration, and contact time. The optimal sorption conditions were determined as pH 2, a solid/liquid ratio of 10 g/L, and a contact time of 800 min. The maximum obtained sorption capacity of the sulfur-impregnated zeolite toward Hg(II) was 1.02 mmol/g. The sorption mechanism of Hg(II) onto the sulfur-impregnated zeolite involves electrostatic attraction, ion exchange, and surface complexation, accompanied by co-precipitation of Hg(II) in the form of HgS. It was found that sulfur-impregnation enhanced the sorption of Hg(II) by 3.6 times compared to the natural zeolite. The leaching test indicated the retention of Hg(II) in the zeolite structure over a wide pH range, making this sulfur-impregnated sorbent a promising material for the remediation of a mercury-polluted environment.

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