Titratable Acidity and Alkalinity of Red Soil Surfaces

The surfaces of red soils have an apparent amphotenc character, carrying titratable acidity and titratable alkalinity simultaneously. The titratable acidity arises from deprotonation of hydroxyl groups of hydrous oxide-type surfaces and dissociation of weak-acid functional groups of soil organic matter, while the titratable alkalinity is derived from release of hydroxyl groups of hydrous oxide-type surfaces. The titratable acidity and titratable alkalinity mainly depended on the composition and content of iron and aluminum oxides in the soils. The results showed that the titratable acidity and titratable alkalinity were in significantly positive correlation not only with the content of amorphous aluminum oxide(Alo) and iron oxide(Feo) extracted with acid ammonium oxalate solution, free iron ox-ide(Fed) extracted with sodium dithionite-citrate-bicarbonate (DCB) and clays, but also with the zero point of charge (ZPC) of the samples. Organic matter made an important contribution to the titratable acidity. The titratable alkalinity was closely correlated with the amount of fluoride ions adsorbed. The titratable acidity and titratable alkalinity of red soils were influenced by parent materials, being in the order of red soil derived from basalt > that from tuff > that from granite. The titratable acidity and titratable alkalinity were closely related with origination of the variable charges of red soils, and to a certain extent were responsible for variable negative and positive charges of the soils.

The pH and Titratable Acidity of Still and Sparkling Flavored Waters: The Effects of Temperature and Storage Time

Statement of the problem: Flavored waters have become increasingly popular in the Trinidadian retail market. There is a paucity of literature on the erosive potential of these products on dental hard tissue. Purpose: This study 1) evaluated the pH and titratable acidity of popular still and sparkling flavored waters in the Trinidadian marketplace and 2) evaluated the effect of time and temperature on pH and titratable acidity. Materials and methods: A calibrated pH meter was used to measure pH at baseline (T0), at one week of storage (T1) and at one month of storage (T2). Titratable acidity was determined using 0.1 M sodium hydroxide until a neutral pH of 7 was attained. Results: All tested flavors of both still and sparkling water demonstrated pH well below the critical pH of 5.5. Reduced temperature and time in storage caused varying degrees of change in both pH and titratable acidity. Generally, the largest changes in titratable acidity occurred for sparkling varieties of water. Conclusion: The still and sparkling flavors of water tested are potentially very erosive to dental hard tissue.

Interaction of Ca^(2+) and soil humic acid characterized by a joint experimental platform of potentiometric titration, UV–visible spectroscopy, and fluorescence spectroscopy

Rocky desertification has become a major environmental issue in the karst region of southwestern China.Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils,despite the relatively higher soil organic matter(SOM)content in limestone soil.The underlying mechanism remains ambiguous.We speculated that the geochemical characteristics of limestone soils in the karst region plays an essential role,especially the high calcium content of limestone soil.To test this hypothesis,we collected limestone soil samples from a limestone soil profile in the southwestern China karst region and extracted humic acid(HA)from these limestone soil samples.We investigated the interaction of Ca^(2+)and three HA samples on a joint experimental platform,which consists of an automatic potentiometric titrator,a UV–visible spectrometer,and a Fluorescence spectrometer.HA solutions were titrated by Ca^(2+)and optical spectra of the HA solutions were monitored during the titration experiments.The results indicated that:(1)the interaction of Ca^(2+)and HA is a combined process of adsorption and complexation.Adsorption dominated the overall distribution behavior of Ca^(2+),which could be fit by Langmuir and Freundlich isotherm models.Complexation was distinguished only when the concentration of Ca2+is low;(2)the changes of UV–visible spectroscopy and excitation–emission matrix fluorescencespectroscopy spectra of HA samples when they were binding with Ca^(2+)implied the apparent molecular size and structure of HA became larger and more complex;(3)the combination of Ca^(2+)and HA plays an important role in the SOM preservation of limestone soils but the stability of the Ca–HA association was relatively weak.The present study draws attention to maintaining the relatively higher Ca^(2+)concentration in limestone soils in ecologic restoration attempts in karst regions.

Determination of Formation Constants of Co￣(2+), Ni￣(2+),Cu￣(2+) and Zn￣(2+) Complexes with Humic and Fulvic Acidsby Potentiometric Titration Method

The formation constants of Co￣(2+), Ni￣(2+), Cu￣(2+) and Zn￣(2+) complexes with humic acid (HA) and fulvicacid (FA) in red soil were determined by the potentiometric titration method. The constants as a functionof composition of the complexation solutions were obtained by two graphical approaches respectively Theformation constants decreased with increasing concentration of metal in the solution. The results provideunambiguous evidence for the heterogeneity of the function groups of humic substances. The formationconstants of FA were much smaller than those of HA, and the formation constants of Cu￣(2+) were muchgreater than those of Co￣(2+) , Ni￣(2+) and Zn￣(2+) . The potentiometric titration method for determining formationconstants are also discussed in the article.

EDTA滴定法准确测定钢铁除锈废酸中锌离子含量

针对钢铁除锈的废酸综合利用过程中锌离子含量不能准确测定的问题,本文提出了一种利用pH控制沉降铁离子,采用EDTA滴定法准确测定钢铁除锈废酸中的锌离子含量的方法,并通过多项式拟合,得到锌离子含量的拟合曲线的回归方程。研究分析了Fe^(3+)、Fe^(2+)对测量结果的影响,提出了解决方法,同时发现加入聚丙烯酰胺(PAM)做絮凝剂可加快Fe^(3+)的沉降。本方法可为此类废酸的综合利用提供检测依据。

电感耦合等离子体原子发射光谱(ICP-AES)法与EDTA滴定法联用测定含白云岩矿石中氟化钙

氟化钙的测定目前较多采用的是国家标准方法GB/T 5195.1—2017和DZG93-05非金属矿萤石分析规程两种方法,前者测定范围≥60%,后者测定范围>3%。两种方法各有优缺点,然而却都无法满足矿石中含有白云岩时的测定。对于萤石矿与白云岩共存样品,直接采用国家标准方法,测定结果偏高,行业标准方法测定的精密度和准确度也很难达到要求。通过对方法进行优化,在样品中加入含钙冰乙酸分离碳酸钙,过滤残渣用混合酸分解后,直接取澄清液在Ca 317.933 nm处,使用电感耦合等离子体原子发射光谱法(ICP-AES)测定氟化钙含量,根据测定结果,将氟化钙质量分数大于15%的样品用EDTA滴定法再次测定。按照实验方法测定实际样品,两种方法测定结果的相对标准偏差(RSD,n=11)分别为1.9%和0.77%,加标回收率为97.9%~102%,可满足含白云岩矿石中氟化钙的准确测定。

QUANTITATIVE ANALYSIS OF VERY WEAK ACID AND BASE BY pH-FIXED TITRATION METHOD

pH-fixed titration method for the determination of weak acids and bases has been studied in this paper.It is not necessary to know the ionization constant of weak acid or base and the concentration of titrant. This method had been applied to determine phenol,4-aminoantipyrine and glycine,whose ionization constants range from 10^(-10)to 10^(-12).The results were satisfactory.

A COMPARISON OF THE DETERMINATION OF STABILITY CONSTANTS OF COMPLEXES OF Cd(Ⅱ)WITH AMINO ACIDS AND SIMPLE PEPTIDES USING MICRO—pH—METRIC TITRATIONS AND CYCLIC VOLTAMMETRY

This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly, Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra- tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol· dm^(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com- puter program and cyclic voltammograms were collected,stored and manipulated using the EG and G CONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible using voltammetry.Evaluation of results from the two techniques suggests that stability constants for the species[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are more reliable when determined by pH-metric titration.

Ag@ZF-(TA-APTES)-Fe^(3+)生物质基复合催化材料的制备及其催化性能

为了有效去除废水中的4-硝基苯酚,在生物质材料竹粉上通过TA/Fe^(3+)原位合成一种新型的银纳米颗粒复合催化材料,采用SEM、XPS、XRD和BET对复合催化材料进行表征,并测试其对4-硝基苯酚的催化还原性能。结果表明:复合催化材料对4-硝基苯酚的催化还原遵循一级反应动力学,随着银负载量、温度及催化剂投加量的增加,催化反应常数均有不同程度的增加;经过10次循环反应后,复合催化材料对4-硝基苯酚的去除率仍在96.5%以上,可见复合催化材料具有良好的稳定性,可多次重复利用。

A two-stage anaerobic system for biodegrading wastewater containing terephthalic acid and high strength easily degradable pollutants

The high strength easily biodegradable pollutants (represented by COD E) are strong inhibitors of terephthalic acid (TA) anaerobic biodegradation. At the same time, TA can inhibit easily biodegradable pollutants removal under anaerobic conditions to a limited extent. This mutual inhibition could happen and cause a low removal efficiency of both TA and COD E, when the effluent from TA workshops containing TA and easily biodegradable pollutants are treated by a single anaerobic reactor system. Based upon the treatment kinetics analysis of both TA degradation and COD E removal, a two stage up flow anaerobic sludge blanket and up flow fixed film reactor(UASB UAFF) system for dealing with this kind of wastewater was developed and run successfully at laboratory scale. An UASB reactor with the methanogenic consortium as the first stage removes the easily biodegradable pollutants(COD E). An UAFF reactor as the second stage is mainly in charge of TA degradation. At a COD E loading of 15.3 g/(L\5d) and a TA loading of 1.4 g/(L\5d), HRT 18.5h, the COD E and TA removal rate of the system reached 89.2% and 71.6%, respectively.

Study of Complexes of Lanthanum with Amino Acids by Titration Calorimeter

The stability constants and thermodynamic functions for complexes of lanthanum with eight kind of amino acids according to 1∶1 and 1∶2 in proportion have been determined by titration calorimeter at 298.15 K. The enthalpy change makes a predominant contribution to the stability of these complexes. The ring in amino acid associated with lanthanum ion helps to enhance the stability of complexes. Steric effects between rings in complexes leads to that the equilibrium constants of reaction of the complexes (1∶2) is much less than that of the complexes (1∶1).

Metal ion-binding properties of L-glutamic acid and L-aspartic acid, a comparative investigation

A comparative research has been developed for acidity and stability constants of M(Glu)1, M(Asp)2 and M(Ttr)3 complexes, which have been determined by potentiometric pH titration. Depending on metal ion-binding properties, vital differences in building complex were observed. The present study indicates that in M(Ttr) com-plexes, metal ions are arranged to the carboxyl groups, but in M(Glu) and M(Asp), some metal ions are able to build chelate over amine groups. The results mentioned-above demonstrate that for some M(Glu) and M(Asp) complexes, the stability constants are also largely determined by the affinity of metal ions for amine group. This leads to a kind of selectivity of metal ions, and transfers them through building complexes accompanied with glutamate and aspartate. For heavy metal ions, this building complex helps the absorption and filtration of the blood plasma, and consequently, the excursion of heavy metal ions takes place. This is an important method in micro-dialysis. In this study the different as-pects of stabilization of metal ion complexes regarding to Irving-Williams sequence have been investigated.

A novel technology for quick acclimation of an anaerobic microbial consortia used for biodegrading teraphthalic acid (TA)

The seed sludge originated from a methane fermentation reactor was enriched and acclimated with TA as sole carbon source under nitrate respiration mode first for 6 week, and then can be turned to methane fermentation conditions. After 6 weeks processing, the specific rate of TA degradation under nitrate respiration mode reached 23.8 mgTA/(L·gVSS), more than two times of that under methane fermentation mode 11.4 mg TA/(L·gVSS). The TA reductive cleavers' population density increased about 6 times and 20 times after 30 days and 90 days acclimation. After a total of 90 days for the enrichment and acclimation, the fermentative bacteria which originally existed in the seed sludge nearly disappeared, and instead of them, the TA reductive and cleaving bacteria group was formed in the new consortia, which was confirmed by the MPN counts and roll tube counts. Compared with the control experiment, the acclimation period can be shortened by about 50%.

Extraction Mechanism of Rare Earths with Sec-Octylphenoxy Acetic Acid by Two-Phase Titration Technique

The compositions of the extracted complexes of La, Gd, Er and Y with sec octyl phenoxy acetic acid in heptane and the related apparent extraction equilibrium constants K M were determined using two phase titration technique. The stoichiometric compounds for La, Gd, Er and Y should be LaA 3·2.5HA, GdA 3·3HA, ErA 3·3.1HA and YA 3·4.3HA respectively. And their p K M are 3.43, 3.46, 3.08 and 2.58 respectively.

Study on the influence factors of the photocatalysis degradation of Humic Acid

The effects of Humic Acid (HA) concentration,pH value and aeration on the photocatalysis degradation of HA by the silica gel supported TiO2 were studied.Moreover,the effect of aeration on the generation of hydroxyl radicals are investigated.The experimental results indicated that the hydroxyl radicals are generated during the photocatalysis process.The generation of hydroxyl radicals is increasing linearly with the reaction time,approximately.Moreover,the generation rate of hydroxyl under the condition of aeration is 1.57 times of that under the condition without aeration,which is the main influent factor on the reaction rate.Therefore,the reaction rate constant with and without aeration is 0.012 min-1 and 0.0063 min-1,respectively.The degradation rate decreases when the initial HA concentration increases,which is due to that more TiO2 active sites are occupied by HA when the HA concentration is higher.Moreover,HA can absorb large amount of photons,which can prevent those available photons to arrive at the activate TiO2 particles.The degradation rate decreases when increasing pH value,which is due to that the adsorption of HA on the TiO2 particles is weakened and not benefit for the degradation process of HA.

THE INTRINSIC ACIDITY CONSTANTS AND SPECIFIC SURFACE AREA OF MARINE SOLID PARTICLES I. A NEW METHOD

This paper proposes a new method for determining the intrinsic acidity constants K and K The new method is a great improvement over the modified Langmuir plot method generally adopted in that determination of these constants is not dependent on the specific surface area S of the marine solid particles. The new method was used to determine K, K and S for the main inorganic components of marine solid particles, including illite, montmorillonite, kaolinite, goethite, y-AlOOH. amorphous ferric oxide, MnO2, manganite, SiO 2 and calcium carbonate, and can facilitate the study on the effect of solution constituents, solution temperature, ionic strength, etc. on the value

Determination of pKa values of alendronate sodium in aqueous solution by piecewise linear regression based on acid-base potentiometric titration

As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.

Numerical Method for Determination of Composition of Weak Acid Mixtures by Potentiometric Titration

An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixtures were determined. The advantages of this treatment were demonstrated by analyzing binary mixtures of chloroacetic, formic and acetic acids.

Investigation of the Reaction Mechanism of Itaconic Acid/Maleic Acid Copolymer System and Cotton Cellulose

The reaction mechanism of IA/MA copolymer system andcotton cellulose is conjectured and verified, the two keysteps, such as the formation of cyclic anhydride interme-diates and the building of ester crosslinklng, and the ef-fect of sodium hypophosphite are especially emphasized,by FT - IR spectroscopy and acid- base titration anal-yses. The experiments reveal that carboxylic acids main.ly change to cyclic anhydride in the pre - drying step andSodium Hypophosphite (SHP) has effect on it, but mostester - crosslinkages are built in the curing step and SHPhas effects on both anhydride formation and ester -crosslinking formation.