Elution Behaviour of Monocarboxylic Acids on a Cation-exchange Resin Column

The retention mechanism of monocarboxylic acids on a cation-exchange resin column was investigated. It was assumed that both Donnan membrane equilibrium and adsorption equilibrium were involved in the chromatographic process. On the basis of the proposed mechanism, an equation was derived for correlating distribution coefficient, Kd, dissociation constant, Aa, and adsorption equilibrium constant, K, of the analyzed acid. By this approach, retention data for some aliphatic acids under different operating conditions were predicted. Results are reasonably in agreement with experiment.

Impact of Hydrogen Ion Concentration on Amino Acids Composition of Macadamia Protein: Approached Using Cation-Exchange Chromatography

In the present context, the objective of this study was to synthesize and analyze the content of AA of macadamia protein and the impact of hydrogen ion concentration (pH) on AA composition. The determination of AA mainly by cation-exchange chromatography was also investigated. Reproducible and reliable techniques for quantification and identification of AA usually require derivatization. However, techniques such as AA analyzer are composed of cation-exchange chromatography and other components can sideline the derivatization with significant accuracy. The present analysis revealed a higher concentration of essential amino acids especially acidic AA, Glu and Asp and basic AA, Arg than other AA in macadamia protein. The study constitutes first report of use of bubble chart for evaluation of AA and explaination of AAS. The results may elaborate that the degradation of AA of macadamia protein for extraction of pH 11 is caused by the impact of pH. Moreover, the nutritional values of AA present in macadamia protein could change for the better by adjusting pH of extraction.

ENCAPSULATION OF STRONG SOLID ACID NANOPARTICLES IN MESOPOROUS CHANNEL HOSTS

Mesoporous molecular sieve with Al-promoted sulfated rirconia (SZA) based strong solid acid nano-particles within its mesoporous channels was synthesized by using a one-step incipient wetness impregnation method with zirconium sulfate and aluminum sulfate as the precursors. The assemblies of SZA/MCM-41 were obtained by thermal decomposition of the precursors in air.The resultant composite was characterized with various techniques such as nitrogen physisorption, X-ray diffraction, SEM and TEM. It was shown that the well-ordered channels of MCM-41 arranged in hexagonal arrays as well as the hollow tubular morphology was retained. The strong solid acid nanoparticles were isolated born each other and highly, dispersed in the channels. Nitrogen sorption showed the expected decrease in pore volume. The catalytic activity of SZA/MCM-41 composite in the isomerization of n-butane was dramatically improved in comparison to bulk SZA or SZA/silica.

Adsorption behavior and mechanism of cadmium on strong-acid cation exchange resin

The adsorption behavior of Cd2+ on 001×7 strong-acid cation exchange resin was studied with the static adsorption method. The adsorption process was analyzed from thermodynamics and kinetics aspects. The influences of experimental parameters such as pH, temperature, initial concentration and adsorption rate were investigated. The experimental results show that in the studied concentration range, 001×7 resin has a good sorption ability for Cd2+, and the equilibrium adsorption data fit to Freundlich isotherms. The adsorption is an exothermic process which runs spontaneously. Kinetic analysis shows that the adsorption rate is mainly governed by liquid film diffusion. The best adsorption condition is pH 4-5. The saturated resin can be regenerated by 3 mol/L nitric acid, and the desorption efficiency is over 98%. The maximal static saturated adsorption capacity is 355 mg/g (wet resin) at 293 K. The adsorption mechanism of Cd2+ on 001×7 resin was discussed based on IR spectra.

Adsorption equilibrium, kinetics, and dynamic separation of Ca2+ and Mg2+ ions from phosphoric acid–nitric acid aqueous solution by strong acid cation resin

The separation of Ca2+and Mg2+ions from phosphoric acid-nitric acid aqueous solution is very significant for the neutralization process of nitrophosphate fertilizer.This paper studied the adsorption equilibrium,kinetics,and dynamic separation of Ca2+and Mg2+ions by strong acid cation resin,and the effects of phosphoric acid and nitric acid on the adsorption process were investigated.The results reveal that the adsorption process of Ca2+and Mg2+ions in pure water on resin is in good agreement with the Langmuir isotherm model and their maximal adsorption capacities are 1.86 mmol·g-1 and 1.83 mmol·g-1,respectively.The adsorption kinetics of Ca2+and Mg2+ions on resin fits better with the pseudo-first-order model,and the adsorption equilibrium in pure water is reached within 10 min contact time,while at the present of phosphoric acid,the adsorption rate of Ca2+and Mg2+ions on resin will go down.The dynamic separation experiments demonstrate that the designed column adsorption is able to undertake the separation of metal ions from the mix acids aqueous solution,but the dynamic operation should control the flow rate of mix acid solution.Besides nitric acid solution was proved to be effective to completely regenerate the spent resin and achieve the recyclable operation of separation process.

Determination of Molecular Mass of Strong Acids by Differential Temperature Model (DTM) Using H₃PO₄and HBF₄for Classical Demonstration

A new chemical hypothesis based on the differential temperature model (DTM) for estimation of molecular masses of some strong acids (H2SO4, HNO3 and HCl) in solutions have previously been propounded and tested theoretically and analytically by the author. The results were published in the Bulletin of Pure and Applied Sciences–Chemistry in 2012. The changes in temperature following various dilutions of the acids were found to be proportional to their molecular properties. The new chemical hypothesis and model is hereby tested on H3PO4 and HBF4 and their exact molecular masses have been evaluated analytically and theoretically. The validity of the hypothesis and the model is hereby presented for chemical proof and adoption to theory by chemists.

Removal of Co(Ⅱ) from aqueous solutions by NKC-9 strong acid resin

A strong acidic ion exchange resin(NKC-9)was used as a new adsorbent material for the removal of Co(Ⅱ)from aqueous solutions.The adsorption isotherm follows the Langmuir model.The maximum adsorption capacity of the resin for Co(Ⅱ)is evaluated to be 361.0 mg/g by the Langmuir model.It is found that 0.5 mol/L HCl solution provides effectiveness of the desorption of Co(Ⅱ)from the resin.The adsorption rate constants determined at 288,298 and 308 K are 7.12×10-5,8.51×10-5and 9.85×10-5s-1, respectively.The apparent activation energy(Ea)is 12.0 kJ/mol and the adsorption parameters of thermodynamic are-H Θ=16.1 kJ/mol,-SΘ=163.4 J/(mol·K),-G Θ 298 K=-32.6 kJ/mol,respectively.The adsorption of Co(Ⅱ)on the resin is found to be endothermic in nature.Column experiments show that it is possible to remove Co(Ⅱ)ions from aqueous medium dynamically by NKC-9 resin.

DIRECT TITRATION OF VERY WEAK ACIDS(BASES)IN AQUEOUS SOLUTION WITH STRONG BASES(ACIDS)USING VISUAL END-POINT INDICATION WITHOUT INDICATOR

This paper reports a new method of titration for very weak acids and bases using the appearance of incisions on oscillopolarogram to indicate the end-point.This method has the advantages of rapidity,simplicity,no indicator needed as well as good precision.

Clinical Evaluation of an Oral Electrolyte Solution Formulated Based on Strong Ion Difference (SID) and Using Propionate as the Organic Anion in the Treatment of Neonatal Diarrheic Calves with Strong Ion Acidosis

Background: It is postulated that the concentrations of the major strong ions (Na, K, and Cl) in oral electrolyte solutions play a major role in clinical efficacy of these solutions for rehydration and corrections of metabolic acid base derangements. Objectives: The purpose of this study was to test prospectively the efficacy of an OES (OESexp) formulated based on concentration of strong ion difference (SID) and propionate in a group of calves with naturally occurring neonatal diarrhea and clinically detectable dehydration and acid base abnormalities. Animals: Ten client owned calves of varying breeds, 2 - 22 days old, presented to a veterinary teaching hospital with a history of naturally occurring acute undifferentiated diarrhea, progressive depression and dehydration for treatment. Methods: Clinical and laboratory parameters were measured pre and post two oral electrolyte treatments to assess efficacy of the experimental OES to correct clinical and clinico pathological parameters. For the clinical trial the calves served as their own controls. For control of safety of medication 4 normal calves were force fed 4 L of OESexp and followed over a 24 hour period. Results: All calves had severe diarrhea and metabolic acidosis. The metabolic acidosis observed in the plasma of these calves and reflected by pH, HCO3- SID and base deficit was corrected significantly towards reference ranges (p < 0.05) with two 2 L feedings 12 hours apart. Dehydration was significantly corrected and all calves were discharged 1 - 3 days post admission. Conclusion and Clinical Importance: The use of SID is a valid approach when formulating oral electrolytes solutions for use in calves with acute diarrhea and metabolic derangement. Sodium propionate is valid substitute for commonly used sodium base equivalents in North America in oral electrolyte solutions.

Rapid analysis of metal ions and organic compounds in strong acidic solutions by nano-ESI mass spectrometry

Rapid analysis of metal ions and organic compounds in strong acidic solutions is of sustainable interest in multiple disciplines.However,complicated and time-consuming pretreatments are always required for MS analysis of the compounds in strong acidic solutions.Otherwise,it will result in a weak signal and cause serious damage to the mass spectrometer.Herein,a simple method inherited from nano-ESI MS was developed for rapid analysis of strong acidic solutions.Nanoliter(nL)strong acidic solution was first loaded in the nano-ESI emitter,followed by evaporation to remove the H+and leave the analytes on the wall of the nano-ESI emitter.The evaporation process can be completed within 1 min because of the extremely tiny volume(≤1 nL)of the loaded solution.Then,the dried analytes on the wall of the nano-ESI emitter were redissolved by loading a new solvent,followed by nano-ESI MS analysis.By using this method,metal ions and organic compounds in the strong acidic solution can be detected with low sample consumption(1 nL),high speed(<2 min/sample),high sensitivity(limit of detection=0.2µg/L),and high accuracy(>90%).Proof-of-concept applications of the present method have been successfully achieved for the analysis of gastric juice(pH of the sample=1),monitoring reaction catalyzed by strong acid(pH of the system=0),and micro-area analysis of ores(pH of the extraction solvent=0),showing great application potential in multiple fields.

Acetalization of carbonyl compounds with 2,2,4-trimethyl-1,3-pentanedio catalyzed by novel carbon based solid acid catalyst

The synthesis of 2, 4-diisopropyl-5,5-dimethy1- 1.3-dioxane through the acetalization of isobutyraldehyde with 2, 2, 4-trimethy1-1,3-pentanediol （TMPD） catalyzed by the novel carbon based acid was first carried out. High conversion （≥98%） and specific selectivity were obtained using the novel carbon based acid, which kept high activity after it was reused 5 times. Moreover. the catalyst could be used to catalyze the acetalization and ketalization of different aldehydes and ketones with superior yield. The yield of several products was over 90%. The novel heterogeneous catalyst has the distinct advantages of high activity, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the success of the green process greatly.

Removal of Ni(Ⅱ) from strongly acidic wastewater by chelating precipitation and recovery of NiO from the precipitates

Strongly acidic wastewater produced in nonferrous metal smelting industries often contains high concentrations of Ni(Ⅱ), which is a valuable metal. In this study, the precipitation of Ni(Ⅱ) from strongly acidic wastewater using sodium dimethyldithiocarbamate(DDTC) as the precipitant was evaluated. The effects of various factors on precipitation were investigated, and the precipitation mechanism was also identified. Finally, the nickel in the precipitates was recovered following a pyrometallurgical method. The results show that, under optimised conditions(DDTC:Ni(Ⅱ) molar ratio = 4:1;temperature = 25 ℃), the Ni(Ⅱ) removal efficiency reached 99.3% after 10 min. In strongly acidic wastewater, the dithiocarbamate group of DDTC can react with Ni(Ⅱ) to form DDTC –Ni precipitates. Further recovery experiments revealed that high-purity Ni O can be obtained by the calcination of DDTC –Ni precipitates, with the nickel recovery efficiency reaching 98.2%. The gas released during the calcination process was composed of NO_(2), CS_(2), H_(2)O, CO_(2), and SO_(2). These results provide a basis for an effective Ni(Ⅱ) recovery method from strongly acidic wastewater.

A pyrazine based metal-organic framework for selective removal of copper from strongly acidic solutions

The selective capture of copper from strongly acidic solutions is of vital importance from the perspective of sustainable development and environmental protection.Metal organic frameworks(MOFs)have attracted the interest of many scholars for adsorption due to their fascinating physicochemical characteristics,including adjustable structure,strong stability and porosity.Herein,pz-UiO-66 containing a pyrazine structure is successfully synthesized for the efficient separation of copper from strongly acidic conditions.Selective copper removal at low pH values is accomplished by using this material that is not available in previously reported metal–organic frameworks.Furthermore,the material exhibits excellent adsorption capacity,with a theoretical maximum copper uptake of 247 mg/g.As proven by XPS and FT-IR analysis,the coordination of pyrazine nitrogen atoms with copper ions is the dominant adsorption mechanism of copper by pz-UiO-66.This work provides an opportunity for efficient and selective copper removal under strongly acidic conditions,and promises extensive application prospects for the removal of copper in the treatment for acid metallurgical wastewater.

Clean and effective removal of Cl(-I)from strongly acidic wastewater by PbO_(2)

Recycling strongly acidic wastewater as diluted H_(2)SO_(4) after contaminants contained being removed was previously proposed,however,Cl(-I),a kind of contaminant contained in strongly acidic wastewater,is difficult to remove,which severely degrades the quality of recycled H_(2)SO_(4).In this study,the removal of Cl(-I)using PbO_(2) was investigated and the involved mechanisms were explored.The removal efficiency of Cl(-I)reached 93.38%at 50℃ when PbO_(2)/Cl(-I)mole ratio reached 2:1.The identification of reaction products shows that Cl(-I)was oxidized to Cl_(2),and PbO_(2) was reduced to PbSO_(4).Cl_(2) was absorbed by NaOH to form NaClO,which was used for the regeneration of PbO_(2) from the generated PbSO_(4).Cl(-I)was removed through two pathways,i.e.,surface oxidation and•OH radical oxidation.•OH generated by the reaction of PbO_(2) and OH−plays an important role in Cl(-I)removal.The regenerated PbO_(2) had excellent performance to remove Cl(-I)after six-time regeneration.This study provided an in-depth understanding on the effective removal of Cl(-I)by the oxidation method.

Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

The Stewart approach-the application of basic physicalchemical principles of aqueous solutions to blood-is an appealing method for analyzing acid-base disorders. These principles mainly dictate that p H is determined by three independent variables, which change primarily and independently of one other. In blood plasma in vivo these variables are:(1) the PCO2;(2) the strong ion difference(SID)-the difference between the sums of all the strong(i.e., fully dissociated, chemically nonreacting) cations and all the strong anions; and(3) the nonvolatile weak acids(Atot). Accordingly, the p H and the bicarbonate levels(dependent variables) are only altered when one or more of the independent variables change. Moreover, the source of H+ is the dissociation of water to maintain electroneutrality when the independent variables are modified. The basic principles of the Stewart approach in blood, however, have been challenged in different ways. First, the presumed independent variables are actually interdependent as occurs in situations such as:(1) the Hamburger effect(a chloride shift when CO2 is added to venous blood from the tissues);(2) the loss of Donnan equilibrium(a chloride shift from the interstitium to the intravascular compartment to balance the decrease of Atot secondary to capillary leak; and(3) the compensatory response to a primary disturbance in either independent variable. Second, the concept of water dissociation in response to changes in SID is controversial and lacks experimental evidence. In addition, the Stewart approach is not better than the conventional method for understanding acid-base disorders such as hyperchloremic metabolic acidosis secondary to a chloride-rich-fluid load. Finally, several attempts were performed to demonstrate the clinical superiority of the Stewart approach. These studies, however, have severe methodological drawbacks. In contrast, the largest study on this issue indicated the interchangeability of the Stewart and conventional methods. Although the introduction of the Stewart approach was a new insight into acid-base physiology, the method has not significantly improved our ability to understand, diagnose, and treat acid-base alterations in critically ill patients.

Selective recovery of Cu(II) from strongly acidic wastewater by zinc dimethyldithiocarbamate: Affecting factors, efficiency and mechanism

The selective recovery of copper from strongly acidic wastewater containing mixed metal ions remains a significant challenge.In this study,a novel reagent zinc dimethyldithiocarbamate(Zn(DMDC)_(2))was developed for the selective removal of Cu(II).The removal efficiency of Cu(II)reached 99.6%after 120 min reaction at 30°C when the mole ratio Zn(DMDC)_(2)/Cu(II)was 1:1.The mechanism investigation indicates that the Cu(DMDC)_(2) products formed as a result of the displacement of Zn(II)from the added Zn(DMDC)_(2) by Cu(II)in wastewater,due to the formation of stronger coordination bonds between Cu(II)and the dithiocarbamate groups of Zn(DMDC)_(2).Subsequently,we put forward an innovative process of resource recovery for strongly acidicwastewater.Firstly,the selective removal of Cu(II)fromactualwastewater using Zn(DMDC)_(2),with a removal efficiency of 99.7%.Secondly,high-value CuO was recovered by calcining the Cu(DMDC)_(2) at 800°C,with a copper recovery efficiency of 98.3%.Moreover,the residual As(III)and Cd(II)were removed by introducing H_(2)S gas,and the purified acidic wastewater was used to dissolve ZnO for preparation of valuable ZnSO_(4)·H_(2)O.The total economic benefit of resource recovery is estimated to be 11.54$/m^(3).Accordingly,this study provides a new route for the resource recovery of the treatment of copper-containing acidic wastewater.

Acidity Evaluation of Industrially Dealuminated Y Zeolite via Methylcyclohexane Transformation

The catalytic transformation of methylcyclohexane as an accepted probe reaction to evaluate zeolitic acidity(concentration,strength,and accessibility)is employed to study the acidity and the reactivity of three commercial dealuminated Y zeolites(DAY)with different Si/Al ratios and meso/microporosities,with their properties analyzed by N_(2) adsorption/desorption,pyridine-IR,and hydroxyl-IR spectroscopy technologies.The global activity(conversion)is largely dependent on the concentration of the acid sites,and the activity of the protonic sites in terms of turnover frequency(TOF)reflects the accessibility of acid sites.The products of aromatics and isomers,and the yield of cracking products increase with the increase of concentration of strong protonic sites in zeolite micropores.Moreover,the decrease of aromatics with the reduction of the concentration of acid sites and the diffusion length within DAY zeolites are observed due to the decrease of the secondary reaction.For the same reason,it results in the increasing of C_(7)products and alkenes/alkanes ratios in the cracking products.The high i-C_(4)product selectivity is a unique reflection of the high percentage of very strong acid sites,which is characterized by the hydroxyl-IR band at 3600 cm^(-1).

Comparative Study between Traditional Approach and Physico-Chemical Approach in Acid Base Disorders Interpretation in Critically Ill Patients

Objective: The traditional approach for acid base interpretation is based on Handerson-Hasselbalch formula and includes Base Excess (BE), bicarbonate (HCO3), albumin corrected anion gap. The Physicochemical approach is centered on the Carbon Dioxide tension (PCO2), the strong ion difference (SID), strong ion gap (SIG) = SID apparent-SID effective and totally weak acids (Atot). The study aims to compare between the traditional approach and the physicochemical approach in acid base disorder interpretation. Design: Prospective observational study in an adult Intensive Care Unit (ICU) recruiting six hundred and sixty one patients. Methods: Arterial blood samples were analyzed to measure pH, PaCO2 sodium, potassium, chloride and lactate. Venous blood samples were analyzed to measure ionized calcium, magnesium, phosphorous and albumin. These samples were interpreted by both techniques. Results: Normal HCO3 and BE were detected by traditional approach in 49 cases of which SIG acidosis was detected in 22 cases (46%) and Hyperchloremic acidosis was detected in 29 cases (60%) by physicochemical method. SIG was elevated in 72 cases (58%) of 124 cases with high anion gap acidosis. SIDeff and BE were strongly correlated, r = 0.8, p 0.0001, while SIG and Albumin corrected Anion Gap (ALAG) were moderately correlated r = 0.56, p Conclusion: Both approaches are important for interpretation of the acid base status. Traditional approach identifies the diagnostic description without many calculations and detects body compensatory response to acid base disorders. Physicochemical approach is essential to identify the exact causation and the severity of the acid base disorders.

强缓速低摩阻低伤害纳米均相缓速酸

针对碳酸盐岩储层改造乳化酸高摩阻、稠化酸聚合物残渣伤害问题,首先通过拟三元相图,以非离子型表面活性剂(三苯乙烯基苯酚聚氧乙烯醚)、阳离子型表面活性剂(季铵盐)、助表面活性剂(醇)为原料制备纳米乳液,然后将20%盐酸、5%纳米乳液、0.1%减阻剂(阳离子聚丙烯酰胺)及功能型添加剂混合制得纳米均相缓速酸。采用旋转岩盘仪、扫描电镜、EDS能谱仪、电导率仪、粒度分析仪、界面张力仪、润湿角测定仪、摩阻仪、酸蚀裂缝导流仪、岩心流动仪等评价了纳米均相缓速酸的性能,分析了缓速机理、高酸蚀裂缝导流机理和溶垢机理。结果表明,纳米均相缓速酸是一种内相为油、外相为酸的纳米均相分散体系,粒径分布为8~100 nm;其具备强缓速(缓速率大于90%)、低摩阻(降阻率大于75%)、低黏、低伤害和高酸蚀裂缝导流性能;可同时溶解有机垢和无机垢,对沥青和碳酸盐岩的溶解率分别为6.91%和100%;可解除储层乳化、水锁、润湿改性伤害。纳米均相缓速酸通过带负电纳米乳液吸附在带正电灰岩表面,建立酸岩“隔离屏障”,实现强缓速;通过差异化酸蚀及黏性指进,实现高酸蚀裂缝导流;通过纳米乳液特殊的油水互溶结构,实现有机垢和无机垢的同时解除。该体系在海上油田现场成功应用,增产效果显著,对碳酸盐岩储层深部改造及多重伤害解除具有重要意义。

强非均质砂岩清洁暂堵转向酸化研究:以塔中志留系为例

酸化是低渗砂岩油藏有效开发的主要改造手段之一。塔中志留系储层小层多,非均质性强,酸化中酸液易进入高渗层,导致低渗层改造欠缺,目前尚无合适的砂岩转向酸化技术。本文采用了可完全水溶降解的清洁暂堵粉末,并配合螯合酸解决了非均质砂岩储层均匀酸化难题。通过并联岩心酸化流动仪,研究了清洁暂堵粉末封堵特性和不同级差下暂堵转向酸化能力。室内实验结果表明,清洁暂堵粉末降解主要受温度控制,在超过90℃后完全降解,降解后溶液清澈透明,且呈酸性,有效提升岩心渗透率20%。浓度为0.1%的暂堵粉末随螯合酸注入岩石后,能够形成内外阻挡层,增加暂堵表皮系数,最大封堵压差可达1.87 MPa,是单纯注螯合酸酸的6.7倍。并联岩心酸化实验表明100目清洁暂堵粉末在0.1%使用浓度下适用于渗透率级差小于15的储层,可有效降低岩心渗透率非均质差异,提高低渗岩心改造程度。此外,在塔中11-9井酸化施工中,暂堵转向酸化后增压效果明显,酸化后产量大幅增加。现场试验及应用证明,暂堵转向酸化技术在志留系储层取得了良好的增产改造效果,对长井段非均质砂岩储层酸化均匀改造具有重要的借鉴意义。