Study of the behaviour of various phenolic compounds in the 4-aminoantipyrine and ultraviolet-ratio spectrophotometric methods without and with distillation

It is customary in industrial analysis in the determination of phenols by the 4-aminoantipyrine (4-AAP) and ultraviolet-ratio spectrophotometric methods to report the total of phenolic compounds as phenol. A study was therefore made of the behaviour of 36 representative phenolic compounds in the 4-AAP and UV-ratio methods, with and without distillation, to ascertain the apparent recoveries relative to that for phenol. The Fisher phenol analyser was used for the UV-ratio method, which depends upon the bathochromic shift (from about 270 to about 290 nm) usually obtained when the solution of the phenol is made alkaline. The apparent recoveries by the 4-AAP method both with and without distillation varied from 0 to 100%. The apparent recoveries by the UV-ratio method without distillation varied from 0 to 148%, and those with distillation varied from 0 to 110%. Sixteen of the compounds tested without distillation gave less than 10% recovery by the 4-AAP method and eleven gave less than 10% recovery by the UV-ratio method. The results after distillation indicated that several of the compounds did not distil completely.     

甲基苯基碳酸酯标准品的制备及其定量分析

利用甲基苯基碳酸酯(MPC)歧化反应的可逆性及逆反应在热力学上有利进行的特点,提出了以碳酸二甲酯 (DMC)和碳酸二苯酯 (DPC)为原料,在TiO2/SiO2催化下合成DMC与苯酚酯交换反应的中间产物MPC的新方法。反应产物经减压精馏、碱洗、水洗、干燥等精制处理,得到了纯度较高的MPC标准品。采用气相色谱-质谱法对所制备的MPC样品进行定性分析,结果表明其中还含有少量的苯酚和DPC杂质。卡尔·费休水分测定结果表明,MPC样品中的含水量为0.26%(质量分数)。使用常规气相色谱仪,采用OV-101毛细管色谱柱,以苯甲酸乙酯为内标物,对自制的MPC标准品中的微量苯酚和DPC进行定量分析,苯酚和DPC的含量分别为2.04%和1.59%（均为质量分数）。根据杂质分析结果可知自制的MPC标准品的纯度为96.11%。以此作为标准品,解决了对DMC与苯酚酯交换反应的中间产物MPC的准确定量问题。     

Evaluation of Spinning Cone Column Distillation as a Strategy for Remediation of Smoke Taint in Juice and Wine

Where vineyard exposure to bushfire smoke cannot be avoided or prevented, grape and wine producers need strategies to transform smoke-affected juice and wine into saleable product. This study evaluated the potential for spinning cone column (SCC) distillation to be used for the remediation of ‘smoke taint’. Compositional analysis of ‘stripped wine’ and condensate collected during SCC treatment of two smoke-tainted red wines indicated limited, if any, removal of volatile phenols, while their non-volatile glycoconjugates were concentrated due to water and ethanol removal. Together with the removal of desirable volatile aroma compounds, this enhanced the perception of smoke-related sensory attributes; i.e., smoke taint intensified. Stripped wines also became increasingly sour and salty as ethanol (and water) were progressively removed. A preliminary juice remediation trial yielded more promising results. While clarification, heating, evaporation, deionization and fermentation processes applied to smoke-tainted white juice gave ≤3 µg/L changes in volatile phenol concentrations, SCC distillation of smoke-tainted red juice increased the volatile phenol content of condensate (in some cases by 3- to 4-fold). Deionization of the resulting condensate removed 75 µg/L of volatile phenols, but fermentation of reconstituted juice increased volatile phenol concentrations again, presumably due to yeast metabolism of glycoconjugate precursors. Research findings suggest SCC distillation alone cannot remediate smoke taint, but used in combination with adsorbents, SCC may offer a novel remediation strategy, especially for tainted juice.     

Effect of acidity and alkalinity on the distillation of phenol: interferences of aromatic amines and formaldehyde with the 4-aminoantipyrine spectro-photometric method for phenol

As determined by the 4-aminoantipyrine (4-AAP) spectrophotometric method, the distillation of phenol is quantitative over the range from about pH 6 to very strongly acidic solutions. Recovery from alkaline solutions decreases with increasing alkalinity. Aromatic amines can interfere with the 4-AAP method by producing colors. The extent of the interference varies markedly with different aromatic amines and is much greater for the extraction method than the direct method. The interference can be considerably reduced by distillation from a strongly acidic solution (10 ml of concentrated sulfuric acid per 500 ml); for large amounts of aromatic amines, double distillation may be necessary. Formaldehyde can interfere by reacting with phenol and repressing the color development. This interference can be eliminated by treatment with ammonium sulfate and sodium hydroxide to form hexamethylenetetramine, followed by acidification and distillation.     

Competitive adsorption of organic matter with phosphate on aluminum hydroxide

The effects of orthophosphate on the adsorption of natural organic matter (NOM) on aluminum hydroxide were investigated using three organic compounds as surrogates, including humic acid (HA), phthalic acid, and 2,3-dihydroxybenzoic acid (2,3-DHBA). The adsorption of phthalic acid and 2,3-DHBA was very limited compared to that of HA, whereas their adsorption was reduced much more significantly than that of HA by phosphate. The efficiency of phosphate in reducing HA adsorption increased with increasing phosphate concentration. Phosphate adsorption was slightly reduced by phthalic acid and 2,3-DHBA but moderately suppressed by HA. The adjacent carboxylic groups mainly contributed to the adsorption of humic acid at low pH, while the adjacent phenol groups were responsible for the adsorption of humic acid at high pH. HPLC-SEC and SUVA analysis revealed that HA molecules with high molecular weight were adsorbed preferentially but were easily displaced by the specifically adsorbed phosphate. TM-AFM images revealed that the aggregation of HA molecules and the protonation of carboxylic groups at low pH facilitated the adsorption under acidic conditions. The presence of phosphate increases the coagulant dosage for NOM removal as some sites on the coagulant precipitates become utilized by phosphate.     

电化学氧化法去除苯酚研究

利用氯碱厂报废的DSA电极电解苯酚,结果显示:此电极对一定浓度的苯酚溶液有较好的去除效果.按影响电解效果各主要因素进行筛选,最佳实验条件为:电流密度30mA/cm2,pH10,支持电解质浓度10mg/L,苯酚浓度10mg/L.电解2h后,CODcr的去除率为66.7%,吸光度去除率为90%.     

二氧化钛纳米管阵列光电催化同时降解苯酚和Cr(VI)

采用电化学阳极氧化法在纯钛箔基底上制备了TiO2纳米管阵列,并运用X射线衍射、扫描电镜和电化学工作站对其进行了表征.结果表明,所制样品是锐钛矿相,管径约为100nm,管长约为2μm,在0.5V偏压下光电流最大.以苯酚和Cr(VI)混合溶液为目标污染物,考察了TiO2纳米管阵列光电催化同时去除苯酚和Cr(VI)的反应性能...     

Removal of heavy metal ions by biogenic hydroxyapatite: Morphology influence and mechanism study

Based on the synthesis of hydroxyapatite (HA) with different morphologies, such as nanorod-like, flower-like and sphere-like assembled HA nanorods, a new strategy has been developed for the removal of heavy metal ions such as Pb²⁺, Cu²⁺, Mn²⁺, Zn²⁺. The dependence of removal efficiency on the morphology and the suspended concentration of trapping agent, the removal time and selectivity were evaluated and discussed. The experimental results proved that the removal capacity of flower-like assembled HA nanorods (NAFL-HA) was the best, and the maximum removal ratio for Pb²⁺ ion was 99.97%. The mechanism of Pb²⁺ removal was studied in detail, noting that some metal ions were completely incorporated into hydroxyapatitie to produce Pb-HA. It reveals that the metal ions capture by HA is mainly controlled by sample surface adsorption and co-precipitation, which are directly controlled by sample morphology.     

Determination of phenol in the presence of sulfite (sulfur dioxide) by the 4-aminoantipyrine spectro-photometric method

The interference of sulfite (sulfur dioxide) with the 4-aminoantipyrine (4-AAP) spectrophotometric method for phenol is discussed for procedures without distillation, and with distillation in the absence and presence of copper(II) sulfate. Sulfite represses the color development in all these procedures. Without chloroform extraction, the maximum tolerable amounts of sulfite in the procedures without distillation, distillation without copper(II) sulfate, and distillation with copper(II) sulfate are 15, 10, and 20 mg/100 ml, respectively. For the extraction method, the limits are 4.0, 4.0, and 10 mg/ 100 ml, respectively. Copprer(II) sulfate catalyzes the air-oxidation of sulfite. Phenol can be determined in the presence of large amounts of sulfite by treating with sulfide to form polythionates and thiosulfate; excess of sulfide is removed with copper(II) sulfate, sulfuric acid is added, the phenol is distilled, and the 4-AAP method is applied. Improvements are made in the overall accuracy of the 4-AAP method.     

Inhibition of Phenol from Entering into Condensed Freshwater by Activated Persulfate during Solar-Driven Seawater Desalination

Recently, solar-driven seawater desalination has received extensive attention since it can obtain considerable freshwater by accelerating water evaporation at the air–water interface through solar evaporators. However, the high air–water interface temperature can cause volatile organic compounds (VOCs) to enter condensed freshwater and result in water quality safety risk. In this work, an antioxidative solar evaporator, which was composed of MoS₂ as the photothermal material, expandable polyethylene (EPE) foam as the insulation material, polytetrafluoroethylene (PTFE) plate as the corrosion resistant material, and fiberglass membrane (FB) as the seawater delivery material, was fabricated for the first time. The activated persulfate (PS) methods, including peroxymonosulfate (PMS) and peroxodisulfate (PDS), were applied to inhibit phenol from entering condensed freshwater during desalination. The distillation concentration ratio of phenol (R_D) was reduced from 76.5% to 0% with the addition of sufficient PMS or PDS, which means that there was no phenol in condensed freshwater. It was found that the Cl⁻ is the main factor in activating PMS, while for PDS, light, and heat are the dominant. Compared with PDS, PMS can make full utilization of the light, heat, Cl⁻ at the evaporator’s surface, resulting in more effective inhibition of the phenol from entering condensed freshwater. Finally, though phenol was efficiently removed by the addition of PMS or PDS, the problem of the formation of the halogenated distillation by-products in condensed freshwater should be given more attention in the future.     

Ag/TiO2对含酚废水的光电催化降解

Ag/TiO2对含酚废水的光电催化降解;Ag/TiO2; 光电催化; 苯酚;电解质     

苯酚羟化反应中焦油的分离与分析

利用高速离心、减压蒸馏和萃取等方法分离和定量分析苯酚催化羟化反应中所产生的副产物焦油,讨论各种方法的特点.使用萃取方法系统地考察了各种条件下,以Cu2(OH)PO4为催化剂时苯酚羟化反应体系中焦油的生成量.     

Graphitic solid core carbon nanorods grown on silica sands using electron cyclotron resonance chemical vapor deposition as a highly efficient and green sorbent for removal of phenol derivatives from water sources

In this study, graphitic solid core carbon nanorods (GSCNRs) were, for the first time, anchored to the surface of silica sands through the electron cyclotron resonance chemical vapor deposition method to provide coated silica sands as a new, low-cost, green, and efficient adsorbent for the removal of organic pollutants such as phenol and 2,4-dichlorophenol (2,4-DCP) from aqueous mediums. The characteristics of GSCNRs/SiO₂ were confirmed through Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy techniques. After the optimization of several parameters, the removal efficiency of phenol and 2,4-DCP using 1 g of adsorbent amount, the initial concentration of pollutants (10 mg/L phenol and 15 mg/L 2,4-DCP), a contact time of 10 min (phenol) and 20 min (2,4-DCP), and pH = 7 were 69 and 89%, respectively. The adsorption isotherm models of Langmuir and Freundlich, as well as pseudo-first-order and pseudo-second-order kinetic models, were examined under optimal conditions. Eventually, GSCNRs/SiO₂ was regenerated five times for the removal of phenol and 2,4-DCP. The removal efficiency of the tested contaminants from inlet raw water of a water treatment plant using the proposed adsorbent was investigated.     

Peroxidase catalyzed polymerization of phenol

effect of horseradish peroxidase (HRP) and H₂O₂ concentrations on the removal efficiency of phenol, defined as the percentage of phenol removed from solution as a function of time, has been investigated. When phenol and H₂O₂ react with an approximately one-to-one stoichiometry, the phenol is almost completely precipitated within 10 min. The reaction is inhibited at higher concentrations of H₂O₂. The removal efficiency increases with an increase in the concentration of HRP, but an increase in the time of treatment cannot be used to offset the reduction in removal efficiency at low concentrations of the enzyme, because of inactivation of the enzyme. One molecule of HRP is needed to remove approximately 1100 molecules of phenol when the reaction is conducted at pH 8.0 and at ambient temperature.     

Bifunctional activated carbon with dual photocatalysis and adsorption capabilities for efficient phenol removal

Bifunctional activated carbons (AC) with the abilities of both photocatalysis and adsorption were fabricated via the sol?Cgel route combined with hydrothermal treatment and N₂ reactivation method. TiO₂ was located mainly at the entrance of the surface macropores of AC. Under UV light irradiation, efficient removal of phenol was realized by combination of adsorption and photocatalytic degradation for the obtained bifunctional materials. In insufficient light or dark, phenol removal occurred mainly through adsorption. The prepared bifunctional carbon with a mass ratio of 50 TiO₂ per AC ratio exhibited high efficiency for phenol removal. The total phenol removal capacity of 50TiO₂/AC was almost 5 times of that of pure AC and 6 times of that pure TiO₂ after 10 cycles. The prepared bifunctional carbons possess the advantages of high pollutant removal capability and good recyclability, making them promising for the efficient treatment of lightly polluted aqueous solutions.     

铁酸锰/腐植酸复合材料制备及其对亚甲基蓝吸附性能

采用化学共沉淀法合成了一种腐植酸(Humic Acid,HA)包覆铁酸锰型磁性复合材料(MnFe₂O₄/HA)。采用扫描电子显微镜(SEM)、粉末X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)等技术手段对其进行表征和分析表明,合成产物颗粒大小约200 nm,具有典型的尖晶石结构,腐植酸成功包覆在MnFe₂O₄颗粒表面,饱和磁化强度为34.01 A·m²/kg,在外界低磁场作用下30 s内便可从水溶液分离。 MnFe₂O₄/HA对亚甲基蓝的吸附是一个准二级动力学过程,在2 h达到平衡,较好的符合Langmuir吸附模型。 与MnFe₂O₄相比其对亚甲基蓝的吸附能力显著增强,室温下pH=9时最大吸附量可以达到29.94 mg/g。 MnFe₂O₄/HA可以作为一种有效去除水体中亚甲基蓝污染物的吸附材料。     

THE ROLE OF HUMIC SUBSTANCES IN THE PHOTOCATALYTIC DEGRADATION OF WATER CONTAMINANTS

Abstract

Photocatalysis over irradiated Ti0₂ has been proved to efficiently abate more than 80% of the organic carbon pertaining to a commercial humic acid (HA). The presence of HA up to 50 mg L^?1 has been found to decrease the degradation rate of some model pollutants, namely phenol, 2,4-dichlorophenol and tetrachloromethane. However, the total organic carbon measurements and chloride evolution ensure that the disappearance of the initial pollutants is not due to binding to HA structure, but to an efficient mineralization process. HA' s are able to scavenge both the oxidative and the reductive active species as shown by the inhibiting effect on the rate of disappearance of phenol and 2,4-dichlorophenol (essentially oxidative), and of CCI4 (initially reductive).     

Spectrophotometric determination of phenol by the 4-aminoantipyrine method after steam distillation in a semimicro kjeldahl apparatus in the presence of a large amount of sodium chloride

Phenol is quantified rapidly and accurately by the 4-aminoantipyrine spectrophotometric method after adding 15 g of sodium chloride to a 25-ml sample and distilling in a Semimicro steam distillation apparatus of the Pregl—Parnas—Wagner type. The large amount of sodium chloride provides a saturated solution of the salt during the course of the distillation and causes most of the phenol to be contained in the first few milliliters of distillate. The method has been used to quantify up to 25 mg of phenol per 25 ml.     

Spectroscopic and potentiometric studies on derivatized natural humic acid.

Isolated soil humic acid (HA) and commercial Aldrich HA were derivatized by esterification with methanol-thionyl and acetylation with acetic anhidride, in order to obtain derivatives with selectively blocked carboxyl and phenol groups, respectively. Results obtained by FT-IR spectroscopy and potentiometry show that the methanol-thionyl procedure is a selective, specific and efficient route for blocking carboxyl groups. The good correlation between results obtained by direct potentiometry after HA esterification and by classical calcium-acetate and baryta exchange methods suggests that esterification followed by direct acid-base potentiometric titration can be used as a method for the estimation of carboxyl and phenol group contents. Phenol groups can not be specifically identified by the acetylation method, due to the low selectivity of the acetylation method. The average values of apparent and intrinsic pK of underivatized and derivatized HAs confirm decrease in ionizable groups content due to derivatization and their values are related to the different chemical structures of the acids.     

A non-distillation kjeldahl method for nitrogen based on precipitation as tetraphenylborate

A simple, accurate method for the determination of protein nitrogen by a modification of the Kjeldahl procedure, eliminating the distillation step and weighing ammonium tetraphenylborate (TPB) precipitate directly, is described. The gravimetric factor is favorable, and no standard solutions are required. Interference from mercury catalyst was prevented by conversion to the soluble tetraiodomercurate(II) complex (method 1), removal of the tetraiodomercurate via anion-exchange resin (method 2), or removal of mercury as mercuric sulfide (method 3). Thusc 3 TPB Methods gave rusults as accurate and precise as the usual distillation approach. Values by method 1, averaged 100.5% recovery with a standard deviation of 1.8 ; and by method 2, which is used when large concentrations of mercury are present, they averaged 100.4% with 1.8 std. dev.