Removal of amino acids from water by adsorption on polystyrene resins

The adsorption of eight amino acids, L ‐asparagine, D,L ‐threonine, L ‐lysine, L ‐leucine D,L ‐methionine, L ‐tyrosine, L ‐phenylalanine and D,L ‐tryptophan, on the non‐polar macroporous adsorbents Amberlite XAD‐2 and XAD‐4 (polystyrene–divinylbenzene copolymers) was studied. Equilibrium adsorption experiments were conducted to estimate the types of isotherm and their parameters. The effect the chemical composition and structure of the amino acids on the efficiency of adsorption was evaluated. The influence of pH and ionic strength was also studied. The data of adsorption isotherms of the examined amino acids seemed generally to approach the Freundlich isotherm model. Tryptophan isotherm adsorption data could match in some cases the Langmuir model. The majority of the adsorption isotherms were almost linear. In terms of adsorbed amino acid on both resin surfaces, the amino acids can be ranked thus: D,L ‐tryptophan > L ‐phenylalanine > D,L ‐methionine, L ‐tyrosine > L ‐leucine > L ‐lysine > D,L ‐threonine > L ‐asparagine. In low pH solution, adsorption was generally higher than that at intermediate and high pH values. Generally, as the ionic strength increases, the adsorption of the amino acids increases. © 2001 Society of Chemical Industry     

Extraction equilibria and separation of phenylalanine and aspartic acid from water with di(2‐ethylhexyl)phosphoric acid

The distribution equilibria of single and binary L ‐phenylalanine and L ‐aspartic acid between water and a kerosene solution of di(2‐ethylhexyl)phosphoric acid (D2EHPA) were studied. It was shown that the distribution ratios of phenylalanine generally increased with increasing aqueous pH (2–5) in the D2EHPA concentration range 0.1–0.5 mol dm^?3, but those of aspartic acid decreased with increasing solution pH. Different reaction stoichiometries were proposed for the extraction of phenylalanine and aspartic acid under the conditions studied. The extraction equilibrium constants were obtained. Competitive extraction in binary systems was more apparent in the pH range where the cationic form of amino acids was not predominant. The present results indicated that selective separation of phenylalanine to aspartic acid was possible with this cationic extractant when they were extracted at higher pH and stripped using higher acidity of HCl solution. Copyright © 2006 Society of Chemical Industry     

Reactive solvent extraction of amino acids with cationic extractants

A mixture of amino acids (arginine, phenylalanine, alanine, glycine and aspartic acid) in solution was extracted by four acidic extractants (dinonylnaphthalenesulphonic acid (DNNSA), di(2-ethylhexyl)monothiophosphoric acid (D2EHPA(S)), di(2-ethylhexyl)phosphoric acid (D2EHPA) and Versatic 10) in toluene. The extractive capacity of the organic phase for the amino acids, using DNNSA, D2EHPA(S) and D2EHPA was found to decrease in the order arginine>phenylalanine>alanine>glycine>aspartic acid, although at low pH values phenylalanine>arginine occurred for D2EHPA(S) and D2EHPA. Separation factors derived for pairs of amino acids were in the range 2·0 (glycine–aspartic acid) to 20·1 (alanine–glycine). The extractive and loading capability of the extractants for the amino acids was found to decrease in the order DNNSA>D2EHPA(S)>D2EHPA>Versatic 10, which follows the reverse order of their respective acid dissociation constants. DNNSA was shown to be a promising extractant for the extraction and fractionation of amino acids. © 1998 SCI     

Reuse of a waste adsorbent poly(AAc/AM/SH)‐Cu superabsorbent hydrogel,for the potential phosphate ion removal from waste water: Matrix effects,adsorption kinetics,and thermodynamic studies

The most commonly applied methods for the treatment of used adsorbents is to recover them in acid/alkaline medium or direct enflame them. This work dealt with a new potential and economic method to utilize a waste adsorbent. Poly(AAc/AM/SH) superabsorbent hydrogels have proved to be a good adsorbent for Cu²⁺ ions and after adsorption the hydrogels were recovered in acid medium. In this report, the Cu²⁺ ion adsorbed hydrogel has not undergone any regeneration process and applied directly to phosphate ion adsorption. The Cu²⁺ ions‐loaded poly(AAc/AM/SH) hydrogels, were stable within a wide pH range and suitable for phosphate ion adsorption. The factors affecting the phosphate adsorption, such as pH, ionic strength, contact time, temperature, initial concentration of the phosphate ion, and coexisting ions were systematically investigated. The phosphate adsorption was highly pH dependent; and the maximum adsorption of 87.62 mg/g was achieved at pH 6.1. The adsorption data fitted the Langmuir adsorption isotherm better than the Freundlich isotherm. The concomitant anions show profounder adverse influence on phosphate ion adsorption of poly(AAc/AM/SH)‐Cu hydrogel and the effect follows the order citrate > sulfate > bicarbonate > chloride > nitrate. The thermodynamic parameters including ΔH°, ΔG°, and ΔS° for the adsorption processes of phosphate ions on the gel were also evaluated, and the negative ΔG° and ΔH° confirmed that the adsorption process was spontaneous and exothermic. The adsorption kinetic results suggest that the adsorption process was well described by the pseudo second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of harvest date and maturity upon free amino acid levels in three varieties of peanuts

An improved method for the extraction of free amino acids and a peptide of unknown composition with a methanol:chloroform:water mixture (60:25:15; v:v:v) was described. The largest variations were related to maturity. If the amino acids were ranked in descending order, glutamic acid, followed by asparagine (including asparagine, glutamine, threonine, and serine), topped the list in the mature and low intermediate groups, except in Valencia at 141 days. The peptide and phenylalanine were usually in the top six, while aspartic acid occurred there fairly often. Arginine was the highest in immature peanuts. Proline was found in higher concentrations in immature peanuts than previously reported. The presence of two nonprotein amino acids (γ-methyleneglutamine and γ-methyleneglutamic acid) in mature kernels was confirmed. Presented at the AOCS Spring Meeting, New Orleans, May 1973. Journal article 2635 of the Oklahoma Agricultural Experiment Station.     

Site-energy distribution analysis of humic acids adsorption by zeolitic tuff

Within a research program aimed to utilize natural zeolites for pedotechnical purposes, such as to rebuild degraded soils, to improve soil fertility and to remove soil pollutants, the adsorption process of humic acids (HAs) on untreated Neapolitan Yellow Tuff and on Ca²⁺-enriched samples was investigated in the temperature range 1–45°C. Experimental data showed a negligible temperature effect indicating that ΔH ≈ 0. Moreover, Scatchard-like plots suggested the occurrence of more than one adsorption sites for both samples. A good fit of the adsorption isotherms was obtained by two-site Langmuir equation. For both sites the HAs affinity was not modified by Ca²⁺-enrichment and ΔS° was >0. The adsorption of HAs on tuff is an entropy-driven process.     

天冬甜精中间体的合成优化

用均匀设计法优化了天冬甜精中间体———N 乙氧硫羰基天冬氨酸的合成反应条件。优化工艺条件为 :反应温度 72℃ ,n(甲基乙基黄原酸酯 )∶n(天冬氨酸 ) =1 5 0∶1 0 0 ,m(天冬氨酸 )∶m(氢氧化钠 ) =0 5 0∶1 0 0 ,m(水 )∶m(天冬氨酸 ) =4 0 0∶1 0 0 ,m(甲醇 )∶m(水 ) =0 15∶1 0 0。N 乙氧硫羰基天冬氨酸的收率为 88 92 %。     

Sorption of tannic acid on zirconium pillared clay

Zirconium pillared clay (PILC) was prepared using montmorillonite as the base clay. Adsorption of tannic acid (tannin) was studied by a batch equilibrium technique, as a function of adsorbate concentration, temperature, pH, agitation speed, particle size of the adsorbent and ionic strength. The process of uptake is governed by diffusion controlled first‐order reversible rate kinetics. The higher uptake for the pH range 4.0–6.0 was attributed to external hydrogen bonding between phenolic‐OH groups of tannin molecules and the hydrogen bonding sites on the clay. The removal of tannin by adsorption was found to be >99.0% depending on the initial concentration in the pH range of 4.0–6.0. The process involves both film and pore diffusion to different extents. The effects of solute concentration, temperature, agitation speed and particle size on the diffusion rate were investigated. Tannin uptake was found to increase with ionic strength due to the compression of diffuse double layers. The applicability of Langmuir and Freundlich isotherm models has been tested. The maximum adsorption capacity of PILC was found to be 45.8 µmol g^?1 of clay and the affinity constant is 2.9 × 10^?2 dm³ µmol^?1 at 30 °C. Thermodynamic parameters such as ΔG °,ΔH ° and ΔS ° were calculated to predict the nature of adsorption. The isosteric enthalpies of adsorption were also determined and found to decrease with increasing surface coverage. Regeneration with hot water (60 °C) has been investigated for several cycles with a view to recovering the adsorbed tannin and also restoring the sorbent to its original state. Copyright © 2001 Society of Chemical Industry     

Corrosion inhibition of mild steel by alkylimidazolium ionic liquids in hydrochloric acid

The acid corrosion inhibition process of mild steel in 1 M HCl by 1-butyl-3-methylimidazolium chlorides (BMIC) and 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) has been investigated using electrochemical impedance, potentiodynamic polarization and weight loss measurements. Potentiodynamic polarization studies indicate the studied inhibitors are mixed type inhibitors. For both inhibitors, the inhibition efficiency increased with increase in the concentration of the inhibitor and the effectiveness of the two inhibitors are in the order [BMIM]HSO₄ > BMIC. The adsorption of the inhibitors on mild steel surface obeyed the Langmuir's adsorption isotherm. The effect of temperature on the corrosion behavior in the presence of 5 × 10⁻³ M of inhibitors was studied in the temperature range of 303-333 K. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpy of activation (ΔH), entropy of activation (ΔS), adsorption equilibrium constant (K_ads) and standard free energy of adsorption (ΔG_ads) were calculated to elaborate the mechanism of corrosion inhibition.     

N-甲酰-L-天冬氨酸酐的合成研究

N-甲酰-L-天冬氨酸酐是合成阿斯巴甜的中间体,为了减少副产物的生成,探索出工业生产中最佳的反应条件。以甲酸、乙酸酐和L-天冬氨酸为原料,氧化镁为催化剂,合成N-甲酰-L-天冬氨酸酐。探讨了反应温度、反应时间、甲酸、乙酸酐和催化剂的用量对反应收率和产物熔点的影响。结果表明,最佳的反应条件为:反应温度50℃,反应时间5 h,物质的量比n(氧化镁)∶n(甲酸)∶n(乙酸酐)∶n(L-天冬氨酸)=0.01∶1.2∶2.5∶1.0,此时产物的纯度较好,收率为85.5%。     

Formation of polyelectrolyte complex and its adsorption properties

Polyeletrolyte complex formations between two oppositely charged polyions[ionene, poly(vinylbenzyl trimethylammonium chloride), poly(diallyl dimethylammonium chloride), polyaminesulfone, potassium poly(vinyl sulfate), sodium poly(stylene sulfonate), poly(acrylic acid)] have been investigated by conductance and trubidity measurements. It was found that the complex formation of these polyelectrolytes formed in stoichiometry. Adsorption isotherms of water, methanol, acetone, and benzene were determined for the resulting complexes at 25°C with a gravimetric adsorption apparatus. The differences in adsorption can be exclusively ascribed to differences in ion site and hydrophobic circumstances around the ion site, since each complex has a low specific surface area (<1 m²/g). Amount of adsorption increased in the order of water > methanol > acetone > benzene. This order corresponds to that of the polarity of adsorbate.     

Removal of phosphates from aqueous solutions by using bauxite II: the activation study

In this study, acid treatment and heat treatment methods have been investigated in order to enhance the phosphate adsorption capacity of bauxite. For this purpose, a series of bauxites treated with 0.1–1.0 M HCl and another one heated at various temperatures between 200 and 1000 °C were subjected to standardized orthophosphate adsorption tests. Besides determining chemical and mineralogical compositions, TGA and DTA were performed and point of zero net proton charge (PZNPC), surface area, mean particle size and porosity were measured for selected samples. The results have shown that the acid treatment of bauxite has a negative effect on the phosphate adsorption capability. On the other hand, it has been observed that the phosphate adsorption capacity of bauxite could be increased by heating. The optimum heating temperature was determined as 600 °C. Bauxite heated at 600 °C exhibited about an eight‐fold increase in surface area compared with raw bauxite. The results showed that the activation of bauxite occurred via dehydration of boehmite and diaspore, being the hydrated mineral phases. Maximum adsorption efficiencies for ortho‐, tripoly‐ and glycerophosphates were achieved in the slightly acidic pH range. It was found that the adsorption capacities of thermally‐activated bauxite for all phosphate species investigated were higher than that of raw bauxite. But the increase in adsorption efficiency is not proportional to the increase in specific surface area. It was found that the relative adsorptivity of phosphate species investigated is in the order of orthophosphate > tripoly(phosphate) > glycerophosphate. In addition, it was found that the desorption trends of these phosphate species were similar to the results obtained for raw bauxite. Copyright © 2003 Society of Chemical Industry     

The use of wood pulp and radiation‐modified starch in wastewater treatment

Radiation‐induced graft copolymerization of maize starch/acrylic acid has been performed. Also, natural byproduct wood pulp was used after chemical treatment for the removal of metal ions from the investigated wastewater. The surface and structure morphology of the wood pulp and starch/acrylic acid were investigated by scanning electron microscopy and infrared spectroscopy. The physical parameters, such as swelling, gel percentage, and grafting efficiency (%) of starch/acrylic acid copolymer, were studied. The factors affecting the abilities of the prepared materials for removing heavy metal ions and dyes from aqueous solutions were studied. It was found that the maximum metal uptake is in the following sequence: Fe³⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺. The adsorption capacity of such investigated metal ions increases with the increase of pH values. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Removal of Metal Contaminants by Ion‐Exchange Resin Columns,Thala Valley Tip,Casey Station,Antarctica

Abstract

Salinity and low temperature effects on adsorption of contaminant metals from water using an iminodiacetic acid (IDA) ion‐exchange resin, were investigated under dynamic flow conditions. The order of selectivity of the resin (20°C and 0% seawater) was: Cu²⁺> Pb²⁺> Cr³⁺> Ni²⁺>Cd²⁺>Zn²⁺. Low temperature (4°C) had no significant effect on the selectivity of the contaminant metals and salinity only affected selectivity for Cr³⁺ and Cu²⁺. Copper had highest selectivity in all column experiments, except where extensive deprotonation occured. Buffering affected retention of Cr³⁺; possibly due to precipitation or complexation as a result of increase in pH.     

Preparation of a New Polystyrene Supported-Ethylenediaminediacetic Acid Resin and its Sorption Behavior toward Divalent Metal Ions

A new polystyrene-supported ethylenediaminediacetic acid resin has been synthesized through a reaction between the amination of the commercially available 4-chloromethyl polystyrene polymer with ethylenediamine and the subsequent carboxymethylation with monobromoacetic acid, using ethylenediamine as spacer. The chelation behavior of this resin toward the divalent metal ions Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺ in aqueous solutions was investigated. Batch equilibration experiments were carried out as a function of contact time, pH, amount of metal-ion, and polymer mass. The amount of metal-ion uptake of the polymer was determined by using atomic absorption spectrometry (AAS). Results of the investigation revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Cu²⁺ and that the metal-ion uptake follows the order: Cu²⁺ > Zn²⁺ > Ni²⁺ > Pb²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed.     

Natural colorant from the bark of Macaranga peltata: kinetic and adsorption studies on silk

The colour component from the bark of Macaranga peltata has been extracted and, using spectral techniques, the main colouring ingredient has been identified as ellagic acid. The dyeing properties of the extract on silk have been studied. The colour coordinates of the dyed samples were found to be in the yellow–red quadrant of the colour space diagram and the dyed samples exhibited acceptable fastness properties. The effect of temperature and dye concentration on the rate of dyeing has been studied. Adsorption studies revealed that the process fits well with the Langmuir isotherm model. The thermodynamic parameters of the dyeing process have been evaluated using an Arrhenius plot. The experimental results revealed that the adsorption was exothermic and spontaneous in nature, and exhibited first‐order kinetics. Further, the effect of electrolyte on rate of dyeing has also been recorded. The rate of adsorption increases as the disrupting effect of the added electrolyte cation increases and follows the order: Al³⁺ > Ca²⁺ > Na⁺.     

Adsorption of Microamounts of Silver on Manganese Dioxide from Acid Solutions

Abstract

Adsorption of microamounts of silver on manganese dioxide from nitric and perchloric acid solutions has been studied and optimized with respect to shaking time, concentrations of electrolyte, adsorbent, and adsorbate. Maximum adsorp- tion (>99.5%) has been achieved from 0.01 mol/dm³ acid solution using 50 mg oxide at 10^?5 mol/dm³ silver concentration after 30 min shaking. The adsorption decreases with increasing concentration of acid and adsorbate from both the acids. The presence of a 10⁴-fold greater concentration of cyanide, thiocyanate, thiosulfate, and Pb(II) than silver reduces the adsorption drastically. The adsorption of silver follows the Freundlich adsorption isotherm over the entire concentration range investigated from 9.27 × 10^?6 to 2.92 × 10^?3 mol/dm³ with a value of A = 49 mmol/g and 1/n = 0.93. Moreover, the Langmuir adsorption isotherm is also valid except at the lowest and highest concentrations. The values of the limiting adsorption concentrtion (C_m ) have been found to be 1 mmol/g and of the equilibrium constant for adsorption 87 dm³/mol at 23 ± 2°C.     

Cation Exchange and Sorption Properties of Aluminum Phosphate

ABSTRACT

The ion-exchange properties of amorphous aluminum phosphate have been studied in aqueous electrolyte solutions of KCl over a temperature range of 300–320 K. The data were explained by the law of mass action. Sorption of Cu²⁺, Ni²⁺, and Co²⁺ on AIPO₄ was also studied as a function of temperature and concentration, and the data were fitted to Langmuir adsorption equations. In all cases the adsorption was found to increase with increases in temperature and concentration in the selectivity order Cu²⁺ > Co²⁺ > Ni²⁺. Further, the values of Langmuir constants were used to calculate the thermodynamic parameters δS°, δH°, and δG°.     

L-cystein modified bentonite-cellulose nanocomposite (cellu/cys-bent) for adsorption of Cu2+, Pb2+, and Cd2+ ions from aqueous solution

In this study, L-cystein modified bentonite-cellulose (cellu/cys-bent) nanocomposite was synthesized and characterized by XRD, FTIR, SEM with EDS, TGA, and TEM techniques. In order to optimize the process the effect of various operational parameters such as pH, adsorbent dosage, contact time, and temperature were also investigated. The adsorption experiments were carried out in initial concentrations range of 20-100 mg L^?1and the adsorbent affinity for metal ions was found to be in order of Cu²⁺ > Pb²⁺ > Cd²⁺. The optimum pH for adsorption of Cu²⁺ and Cd²⁺ was observed at 5 while for Pb²⁺ it was pH 6. Based on the Langmuir model, the maximum adsorption capacity of Cu²⁺, Pb²⁺, and Cd²⁺ at 50^?C was found to be 32.36, 18.52, and 16.12 mg g^?1, respectively. The Langmuir isotherm and pseudo-second order model were found to be better fitted than the other isotherms and kinetic models. The results of thermodynamic parameters confirmed the process to be endothermic and spontaneous in nature.     

Removal of Zn(II) from aqueous solution with natural Chinese loess: Behaviors and affecting factors

The Chinese loess was proved a promising adsorbent for Zn(II) removal from aqueous solution with adsorption capacities at 70.2-83.2 mg g^− 1 at 15-45 °C. Batch tests were conducted to evaluate the factors affecting the removal efficiency, of which the pH, temperature and initial Zn concentration all found in positive relevance to the increase of Zn(II) removal efficiency except for the slurry concentration. The uptake of Zn(II) on Chinese loess was considered as ion-exchange adsorption based on the calculated adsorption energy at − 12.8 to − 16.18 kJ mol^− 1 by D-R isothermal adsorption model. The adsorption kinetics follows the pseudo-second-order kinetics and the equilibrating duration was found to be > 24 h. Thermodynamic investigation shows that the enthalpy and entropy changes during adsorption are in the range of 18.27-47.83 kJ mol^− 1 and 52.7-129.6 J mol^− 1 K^− 1, respectively. The predicted Gibb's free energies were in the range of − 5.97-3.09 kJ mol^− 1, indicating that the adsorption was in favor of higher temperature and lower initial Zn(II) concentration. The optimal Zn(II) removal efficiency could be obtained under the following conditions: low or intermediate Zn(II) concentration, long reaction time, high temperature and initial pH > 3.0.