Linear Free Energy Relationships in Extraction of Rare Earths by Acidic Organophosphorus Extractants

The correlation relationships of apparent extraction equilibrium constant (1gK(ex)) with the electronic effect parameter( Sigma sigma(Phi)) and the steric effect parameter ( Sigma upsilon ) of the substituents in extractant molecules are investigated by linear regression analysis in the extraction of rare earths by various classes and structures of monoacidic organophosphorus extractants. The results indicate that in Linear free energy relationship formula 1gK(ex) = rho Sigma sigma(Phi) + psi Sigma upsilon + h generally follows for this kind of extraction systems. Accordingly, the quantitative structure-behaviour relationships of extractants are discussed. These relationships can be preliminarily applied to predict the 1gK(ex) values of rare earth extraction with definite structures of this class of extractants, and thus can provide some directions for the design of new RE extractants.

Leaching of phosphorus from incinerated sewage sludge ash by means of acid extraction followed by adsorption on orange waste gel

Ashes from sewage sludge incineration have a high phosphorus content, approximately 8% （W/W）, which indicates a potential resource of the limiting nutrient. Incineration of sewage sludge with subsequent recovery of phosphorus is a relatively new sludge treatment technique. In this article, the leaching of phosphorus by using sulfuric acid as well as hydrochloric acid by means of several batch experiments was presented. At the same time a selective recovery of phosphorus by adsorption was also discussed. The effects of acid concentration, temperature and time on extraction were studied. The phosphorus leaching increased with the increase in acid concentration and temperature. Kinetic studies showed that the complete leaching of phosphorus took place in less than 4 h. Selective adsorption of phosphorus by using orange waste gel provided a hint for recovery of this natural resource, which eventually could meet the ever-increasing requirement for phosphorus. The overall results indicated that the incinerated sewage sludge ash can be treated with acid to efficiently recover phosphorus and thus can be considered a potentially renewable source of phosphorus.

Deep eutectic solvents and alkaline extraction of protein from seabuckthorn seed meal: a comparison study

Seabuckthorn seed meal(SSM) is a waste of oil extraction industry that rich in protein. In order to seek suitable protein extraction method, three different deep eutectic solvents(DESs)(including choline chlorideglycerol, choline chloride-oxalic acid and choline chloride-urea) were developed for extracting protein from SSM and compared with alkaline. Result indicated that alkaline could effectively extract 56.9% protein from SSM and its protein content was 73.1%, higher than DES at 31.0%-41.4% and 64.3%-67.5%, respectively. However, compared to alkali, DES led to a product with less β-sheet, more β-turn, more essential amino acids, higher total amino acid content, especially choline chloride-urea which extracted protein showing an integrated and similar protein weight distribution compared to SSM. Also, this protein extracted chloride-urea showed a highest digestibility in vitro(by pepsin)(54.2%). These results indicated that choline chloride-urea extraction is better than alkaline extraction for SSM.

Synergistic extraction of rare earths by mixture of HDEHP and HEH/EHP in sulfuric acid medium

The extraction of RE（Ⅲ） （RE=La, Nd, Sm, Gd） in sulfuric acid medium using the mixture of HDEHP（H2B2） and HEH/EHP（H2L2） was investigated. The synergistic enhancement coefficient（R） was calculated for La （1.96）, Nd（3.52）, Sm（5.96）, and Gd（5.71）, respectively, at pH=2.0, and it was seen that the R increased with the increase of aqueous quilibrium pH. The configuration of the extracted complexes was considered to be RE（SOa）xH2x（HB2）3 with HDEHP, RE（SOa）xH2x（HL2）3 with HEH/EHP, and RE（HB2）2（HL2） with their mixture as the extractant with the slope method. The equilibrium constants and stability constants were calculated. A cation exchange mechanism was proposed as well.

Study on the Process for Removal of Samarium from NdCl_3 Solution by Solvent Extraction with DEHPA

The process for removal of samarium from NdCl_3 solution containing a little samarium by solvent extrac-tion with unsaponated Di (2-ethyl hexyl) orthosphoric acid (DEHPA) at acidic range is reported. The in-dustrial experiments have been completed on a production line of 150 t Nd_2O_3 per annum in the Baotou ThirdRare Earth Factory. As a result of 9 step counter current extraction , Sm_2 O_3 content in Nd_2 O_3 drops down to0. 08 % from 0. 5% , the purity of neodymium oxide is over 99. 5% and the direct recovery of Nd_2O_3 is 92%～ 93% .

Equilibrium of liquid-liquid extraction of 2-phenylbutyric acid enantiomers: Experiment and model

The utilization of liquid–liquid extraction for the separation of 2-phenylbutyric acid（2-PBA） enantiomers was proposed. Factors affecting the extract process were investigated, including organic solvents, β-cyclodextrin derivatives, cyclodextrin concentration, p H and temperature. A model was proposed to describe the separation process based on the homogeneous phase reaction mechanism. Important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic 2-PBA were0.129 and 7.455, respectively. The equilibrium constants of the complexation reactions were 89.36 and36.78 L·mol^-1 for（＋）-and（-）-2-PBA, respectively. The model was verified by experiments and proved to be an excellent means to optimize the separation system. Through modeling prediction and experiment, the best conditions（e.g., pH value of 3.00, extractant concentration of 0.1 mol·L^-1, temperature of 5.0 ℃） were acquired. Under this condition, the maximum enantioselectivity（2.096） was obtained.

Nickel extraction from low grade laterite by agitation leaching at atmospheric pressure

This research work deals with the extraction of nickel from a low grade nickel laterite ore, taken from a deposit located in southwestern of Iran, through agitation leaching at atmospheric pressure. The assaying and mineralogical studies carried out on the nickel laterite sample, showed the 0.88% Ni, and principally consisted of oxide and silicate crystalline phases i.e. dolomite, quartz, magnetite, and goethite. Among numerous factors affecting such process, four major parameters i.e. temperature, agitator speed(r/min), leaching agents and their concentration were considered in a two-level full factorial experimental design. The agitation leach tests showed that the ore could be leached at atmospheric pressure with sulfuric acid while citric acid was almost unpromising. Analysis of variance(ANOVA) using DX7 software was employed to identify effective parameters. Sulfuric acid concentration and temperature were the most effective parameters on Ni extraction. Furthermore, the factorial models for experiment responses were developed. The results showed 83% Ni extraction after 4 h leaching, under optimized conditions i.e.temperature at 95 ℃, acid concentration at 5 N and agitator speed at 1000 r/min. This study revealed that factorial experimental design can be implemented to identify effective parameters on the agitation leaching process of nickel laterite.

Extraction Separation of Scandium，Iron and Lutetium with Isopropyl Phosphonic Acid Mono（1－hexyl－4－ethyl）OctylEster

The extraction and stripping of scandium from its sulfate solutions by isopropyl phosphonic acid mono (1-hexyl-4-ethyl) octyl ester (PT-2, HL) diluted with n-hexane are reported. A high efficiency of separation between scandium, iron and lutetium can be achieved by controlling aqueous acidity. Different mechanisms of Sc3+ with PT-2 in various acid range have been proposed.At lower aqueous acidity, it is a cation exchange reaction, while at higher acidity. a solvation reaction was ascertained. Its IR and NMR spectra have been discussed. The effect of temperature on extraction of Sc3+ was observed and thermodynamic functions were calculated.

Study on extraction kinetics ofα-cyclopentylmandelic acid enantiomers with hydroxyethyl-β-cyclodextrin as chiral selector

In this work,the kinetic study on reactive extraction ofα-cyclopentylmandelic acid(α-CPMA)enantiomers was performed in a Lewis cell using hydroxyethyl-β-cyclodextrin(HE-β-CD)as chiral selector.The enantioselective complexation equilibrium between HE-β-CD andα-CPMA enantiomers was studied by phase solubility method.The important process parameters affecting the initial extraction rate were separately studied and the reaction rate equations were deduced.The optimal conditions for kinetic study were as follows:stirring speed of 75 r·min^(-1),interfacial area of 12.56 cm^2,pH of 2.5,initial HE-β-CD concentration of 0.05 mol·L^(-1),initialα-CPMA concentration of 5 mmol·L^(-1),and temperature of 278 K.The reaction has been found to be first order inα-CPMA and second order in HE-β-CD with the forward rate constants of 2.056×10^(-3)m^6·mol^(-2)·s^(-1)and 1.459×10^(-3)m^6·mol^(-2)·s^(-1)for(S)-α-CPMA and(R)-α-CPMA,respectively.The complexation equilibrium constants were evaluated as 61 L·mol^(-1) and 117 L·mol^(-1)for(S)-α-CPMA and(R)-α-CPMA,and the intrinsic enantioselectivity is estimated as 1.92.

Separation of Indium and Iron from Dilute Sulphate Solutions with a Phosphorous Mixer Extractant

The phosphorous mixer introduced could replace D2EHPA as an extractant applied in the extraction of indium. The extraction properties of the phosphorous mixer were studied. The influences of extractant concentration, organic/aqueous (O/A) phase ratio, equilibrium time, and pH value of the feed solutions on the extraction of indium, and separation of indium-iron were investigated experimentally. Under the best operating conditions, more than 98% of indium. was extracted through two-stage counter-current extraction. The optimizing condition of indium extraction is determined as follows: O/A = 1 : (9-12) in volume ratio; 30% PPD in sulphonated kerosene; pH of the feed, about 0.6; equilibrium time, 3-5 min. The extractant has good reusing and anti-aging properties.

Bioavailability of heavy metals in soil of the Tieguanyin tea garden, southeastern China

The bioavailability of 22 heavy metals was investigated at 19 sampling sites in Tieguanyin tea garden in Anxi County,Fujian Province,southeastern China.Heavy metal concentrations were determined by inductively coupled plasma-mass spectrometry(ICP-MS)and evaluated by geo-accumulation index(I_(geo)).Dilute nitric acid extraction was used to evaluate biological activity.Cu,Pb,and Cd were highly bioavailable and most easily absorbed by tea trees.Heavy metal bioavailability in the surface soil was as the ratio of the effective state to the total amount.Cd had the highest I_(geo)values,and the respective samples and sites were classified as moderately/strongly contaminated.Cd element is considered the main factor of heavy metal pollution in the tea garden in Anxi.The other heavy metals studied were present in lower concentrations;thus,the samples were classified as uncontaminated or slightly contaminated.

Alumina Recovery from Kaolin with Mineral Impurities

The alumina recovery from low grade kaolin （K-JS） treated through thermal and mechanical methods was investigated. High grade kaolin （K-SX） was used as comparison. The optimum calcination temperatures for K-JS and K-SX were both 600 ℃, which resulted in 89.34wt% of alumina extraction from K-JS and 83.37wt% from K-SX. With the increase in calcination temperature, the chemical reactivity of calcined K-JS and K-SX to acid decreased. Mechanical treatment was much more effective in increasing the alumina extraction from activated kaolin. Around 99wt% of alumina was extracted from K-JS ground for 10 hours and 95wt% of alumina was extracted from K-SX ground for 20 hours. The IR results showed that the substitute of A1 for Si occurred in calcined K-SX, however, the impurities in K-JS decreased this substitute. More alumina could be extracted from low grade kaolin than that from high grade kaolin under identical thermal or mechanical conditions.

Antibacterial and Antioxidant Effects of Three Chlorogenic Acid Extracts

[Objectives] To study the antibacterial and antioxidant effects of chlorogenic acid extracts of Gynura procumbens,Lonicera japonica,and Eucommia ulmoides leaves,and provide a reference for their usage as natural food preservatives and antioxidants. [Methods]The disc diffusion method was applied to study the antibacterial activity of chlorogenic acid extracts of G. procumbens,L. japonica,and E. ulmoides leaves against several common pathogens. In the antioxidant effects,study was carried out on the anti-lipid peroxidation,reducing capacity,and DPPH free radical scavenging capacity of chlorogenic acid extracts of G. procumbens,L. japonica,and E. ulmoides leaves,respectively.[Results]Three chlorogenic acid extracts had strong inhibitory effects on bacteria,especially the inhibition on Staphylococcus aureus. At the concentration of 100 mg/m L,the bacteriostatic ring of chlorogenic acid extracts of G. procumbens,L. japonica,and E. ulmoides leaves reached 21. 4,23. 6 and 24. 7 mm respectively. Besides,these chlorogenic acid extracts had significant inhibitory effect on Escherichia coli and Salmonella,but the inhibitory effect on the yeast was not obvious; the antibacterial intensity of antibacterial compounds was chlorogenic acid extracts of E. ulmoides > chlorogenic acid extracts of L. japonica > chlorogenic acid extracts of G. procumbens. Among these three chlorogenic acid extracts,the chlorogenic acid extracts of E. ulmoides had higher anti-lipid peroxidation,reducing capacity,and DPPH free radical scavenging capacity than other two chlorogenic acid extracts. [Conclusions] This paper reveals that among chlorogenic acid extracts of G. procumbens,L. japonica,and E. ulmoides leaves,the chlorogenic acid extracts of E. ulmoides leaves have a stronger antibacterial activity and antioxidant activity.

Vanadium(Ⅳ)solvent extraction enhancement in high acidity using di-(2-ethylhexyl)phosphoric acid with[Cl^(-)]present:an experimental and theoretical study

Separation of vanadium from black shale leaching solution at low pH is very meaningful,which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss.In this study,coordination mechanism of vanadium in acid leaching solution at low pH was investigated with the intervention of chloride ions.Under the conditions of pH 0.8,di-(2-ethylhexyl)phosphoric acid concentration of 20%,phase ratio of 1:2,and extraction time of 8 min,the vanadium extraction could reach 80.00%.The Fourier transform infrared and electrospray ionization results reveal that,despite the fact that the chloride ion in the leachate could significantly promote vanadium extraction,the chloride ion does not enter the organic phase,indicating an intriguing phenomenon.Among Cl^(-)-V,SO_(4)^(2-)-V,and H_(2)O-V,the V-Cl bond is longer and the potential difference between coordinate ions and vanadium is smaller.Therefore,Vo^(2+)gets easily desorbed with chloride ions and enter the organic phase.At the same time,the hydrogen ions of di-(2-ethylhexyl)phosphoric acid also enter the water phase more easily,which reduces the pH required for the extraction reaction.

Extractability of Cu in Alkaline Biosolids-Amended Soilsas Influenced by γ-Irradiation

An incubation experiment was conducted to investigate themicrobial biomass associated Cu in four contrasting soils to which analkaline stabilised sewage sludge cake was applied. The organisms ofsludge- amended and control soils were killed using γ-irradiationtechnique, and the aqueous and acid-extractable Cu concentrationswere determined. Addition of the sludge product increasedsignificantly the concentration of both the aqueous and diluteHOAc-extractable Cu in all the irradiated soils compared to thenon-sterilised sludge/soil mixtures, but the increase was morepronounced in the dilute acid-extractable Cu, indicating that the Curendered extractable in water and dilute acetic acid by γ-irradiation existed in the both soil liquid and solid phases. Theadditional increase in extractable Cu following the biocidaltreatment is likely to be due to release of Cu from the same fractionof soil microbial biomass.

Clumped Isotope Analysis of Calcite and Dolomite Mixtures Using Selective Acid Extraction

Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.

Enhancing polyphenol extraction from unripe apples by carbohydrate-hydrolyzing enzymes

The effects of process variables such as enzyme types, enzyme ratio, reaction temperature, pH, time, and ethanol concentration on the extraction of unripe apple polyphenol were investigated. The results indicated that Viscozyme L had the strongest effect on polyphenols extraction and was selected to study the polyphenol composition. The ratio of enzyme （Viscozyme L） to sobstrate （2 fungal beta-glucanase units （FBG）） at 0.02, reaction at pH 3.7, 50℃ for 12 h, and ethanol concentration of 70% were chosen as the most favorable extraction condition. Total phenolic content （TPC）, reducing sugar content （RSC）, and extraction yield increased by about 3, 1.5, and 2 times, respectively, compared with control. The contents ofp-coumaric acid, ferulic acid, and caffeic acid increased to 8, 4, and 32 times, respectively. The enzyme-aided polyphenol extraction process from unripe apples might be applied to food industry for enhancing bioactive compound production.

Extraction and separation of heavy rare earths from chloride medium byα-aminophosphonic acid HEHAPP

The extraction and separation of heavy rare earths（REs） using newly synthesized a-aminophosphonic acid extractant 2-ethylhexyl-3-（2-ethylhexylamino）pentan-3-yl phosphonic acid（HEHAPP, HA） in nheptane were investigated from chloride medium. The extraction stoichiometries of lanthanum, gadolinium, yttrium and lutetium are determined to be REA3 by the slope analysis method. The favorable separation factors of adjacent heavy REs（Ⅲ）,i.e. β（Y/Ho）, β（Er/Y）,β（Tm/Er）,β（Yb/Tm） and β（Lu/Yb）, are determined to be1.87,1.36, 3.21,3.22 and 1.93, respectively, when extracted from a binary system at proper condition. The loading capacities of HA for Ho, Er, Yb and Lu increase in the order Ho 〈 Er 〈 Yb 〈 Lu with the values being 0.201, 0.205, 0.216 and 0.229 mol/L, respectively. So HA would be a potential extractant for the separation of heavy REs（Ⅲ）. Among inorganic acids such as H2 SO4, HNO3 and HCl, HCl is tested to be the most effective stripping agent.

Solvent extraction and separation of light rare earth elements (La, Pr and Nd) in the presence of lactic acid as a complexing agent by Cyanex 272 in kerosene and the effect of citric acid,acetic acid and Titriplex Ⅲ as auxiliary agents

At present, the use of rare earth elements（REEs） has become an inevitable necessity in many modern industries. In general, liquid extraction is the best commercial method for extracting REEs due to its ability to control high volumes of liquids with electrical load. With the aim of improving a separation technology that would be superior to the existing extraction systems, the extraction behaviors of La（Ⅲ）,Pr（Ⅲ）, and Nd（Ⅲ） from an HCI medium with Cyanex 272 in the presence of the complexing agent lactic acid（HLac） and auxiliary agents citric acid（H3 Cit）, acetic acid（HAc）, and Titriplex Ⅲ have been reported.The effect of pH and lactic acid concentration has been examined. The use of lactic acid as a complexing agent leading to a high extraction of REEs with Cyanex 272 at pH = 5 was compared with systems without lactic acid. The results show that the use of acetic acid along with lactic acid leads to an increase in the extraction percentage of LREEs. While use of citric acid and Titriplex Ⅲ reduces the extraction percentage of LREEs. Finally, the presence of Titriplex Ⅲ together with lactic acid could lead to an increase in the separation factor of Pr and Nd.

Multi-walled carbon nanotube as a solid phase extraction adsorbent for analysis of indole-3-butyric acid and 1-naphthylacetic acid in plant samples

In this work, a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples, Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube （MWCNT） was chosen as the adsorbent for the extraction of auxins from plant samples. In this study, two important auxins were selected as model analytes, namely indole-3- butyric acid （IBA） and 1-naphthylacetic acid （NAA）. They could be extracted and concentrated due to their π-π stacking interactions with MWCNT. Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment. Factors that may affect the enrichment efficiency were investigated and optimized. Comparative studies showed that MWCNT was superior to CI 8 for the extraction of the two analytes. Validation experiments showed that the optimized method had good linearity （0.9998 and 0.9960）, high recovery （81.4%-85.4%）, and low detection limits （0.0030 mg/L and 0.0012 mg/L）. The results indicated that the novel method had advantages of convenience, good sensitivity, high efficiency, and it was feasible for the determination of auxins in plant samples.