Preparation and Characterization of a Novel Spherical Cellulose Adsorbent for Reduction Adsorption of Trichloroacetic Acid

A novel spherical cellulose adsorbent has been prepared by homogeneous graft polymerization of N,N＇-methylenebisacrylamide （MBA） onto cellulose in an ionic liquid, 1-N-butyl-3-methylimidazolium chloride （BMIMC1）, which was then partially amine methylated through Mannich reaction to get bifunctionalized materials containing both amide and sulphinate moities. Factors affecting the attachment of functional groups were investigated. The adsorbent was characterized by Elemental Analysis （EA）, Fourier Transform Infrared Spectroscopy （FTIR） and Scanning Electron Microscope （SEM）. Cellulose adsorbent was then tested for its potential applications in the reduction adsorption oftrichloroacetic acid （TCAA） from aqueous solutions.     

固相萃取-离子色谱法测定饮用水中的痕量卤代乙酸

建立了固相萃取-离子色谱(SPE-IC)测定饮用水中痕量卤代乙酸(HAAs)(包括一氯乙酸、二氯乙酸、三氯乙酸、一溴乙酸和二溴乙酸)的方法。固相萃取采用LiChrolut EN SPE柱来进行痕量待测物的预浓缩（25倍）和基体杂质的消除,用NaOH(10 mmol/L)洗脱;色谱分离采用亲水性、高容量、氢氧化物选择型阴离子交换柱Dionex IonPac AS16(250 mm×4 mm i.d.),以NaOH为流动相进行浓度梯度淋洗,淋洗速度为0.8 mL/min,电导检测,进样量为500 μL。结果表明,用SPE-IC法测定HAAs,一溴乙酸的检测限为12.5 μg/L,其余4种HAAs的检测限为0.38~1.69　μg/L。该法可实现对饮用水中痕量卤代乙酸的测定。     

The use of trichloroacetic acid imprinted polymer coated quartz crystal microbalance as a screening method for determination of haloacetic acids in drinking water

An alternative screening method for haloacetic acids (HAAs) disinfection by-products in drinking water is described. The method is based on the use of piezoelectric quartz crystal microbalance (QCM) transducing system, where the electrode is coated with a trichloacetic acid-molecularly imprinted polymer (TCAA-MIP). This MIP comprises a crosslinked poly(ethyleneglycoldimethacrylate-co-4-vinylpyridine). The coated QCM is able to specifically detect the analytes in water samples in terms of the mass change in relation to acid-base interactions of the analytes with the MIP. The TCAA-MIP coated QCM showed high specificity for the determination of TCAA in aqueous solutions containing inorganic anions, but its sensitivity reduced in water samples containing hydrochloric acid due to a mass loss at the sensor surface. Cross-reactivity studies with HAA analogs (dichloro-, monochloro-, tribromo-, dibromo-, and monobromo-acetic acids) and non-structurally related TCAA molecules (acetic acid and malonic acid) indicated that recognition of the structurally related TCAA compounds by the TCAA-MIP-based QCM is due to a carboxylic acid functional group, and probably involves a combination of both size and shape selectivity. The total response time of sensor is in the order of 10 min. The achieved limits of detection for HAAs (20-50 μg l⁻¹) are at present higher than the actual concentrations found in real-life samples, but below the guidelines for the maximum permissible levels (60 μg l⁻¹ for mixed HAAs). Recovery studies with drinking water samples spiked with TCAA or spiked with mixtures of HAAs revealed the reproducibility and precision of the method. The present work has demonstrated that the proposed assay can be a fast, reliable and inexpensive screening method for HAA contaminants in water samples, but further refinement is required to improve the limits of detection.     

饮用水新型含氮消毒副产物卤乙酰胺稳定性研究

饮用水氯化消毒工艺向氯胺消毒工艺的转变, 降低了三卤甲烷(THM)和卤乙酸(HAA)等消毒副产物(DBP)的浓度, 但增加了毒性更强的含氮消毒副产物(N-DBP)含量, 卤乙酰胺(HAcAm)便是其中的代表. 本研究结合线性自由能关系(LFER)理论, 考察了HAcAm在不同pH条件下的水解特性, 以及不同氯投加量条件下的氯化特性, 并探讨了HAcAm的水解和氯化反应路径. 结果表明, 在较强的酸性条件下(pH＝4)二氯乙酰胺(DCAcAm)将发生水解反应, pH＝5时DCAcAm较为稳定, 三氯乙酰胺(TCAcAm)在酸性条件下未产生明显的水解现象; 碱性环境中TCAcAm和DCAcAm皆发生明显水解反应, 反应符合一级动力学, 保存DCAcAm和TCAcAm水样时需调pH至5左右. 氯化消毒会产生较高浓度的THM和HAA, 但可能会缩减毒性更强的HAcAm等N-DBP在饮用水中的含量. pH＝10时TCAcAm水解后快速生成三氯乙酸(TCAA); 而对于氯化反应, TCAcAm与HOCl反应生成较为稳定的中间产物Cl-N-TCAcAm, 当HOCl浓度较高时, Cl-N-TCAcAm进一步与HOCl反应生成TCAA.     

离子色谱-串联电喷雾质谱法检测自来水中二氯乙酸和三氯乙酸

建立了一种采用离子色谱-串联电喷雾四级杆质谱联用技术检测自来水中可致癌的饮用水消毒副产物二氯乙酸和三氯乙酸的方法。该方法使用IonPacPrototype-10高容量阴离子交换柱为分离柱,以ICS-3000多功能色谱系统的淋洗液自动发生装置在线产生不同浓度的KOH淋洗液,在合适的梯度条件下,实现对自来水样品中两种卤代乙酸和多种常见阴离子的高效分离,经抑制器将淋洗液抑制为近中性后,在不添加有机溶剂的情况下,进入API3200 ESI-MS/MS质谱系统,选取适合的离子对和温度、能量条件,进行准确定量分析。在优化的色谱和质谱条件下,二氯乙酸和三氯乙酸的检出限分别为0.053和0.46μg/L。峰面积校正曲线的线性范围均跨越两个数量级以上。对4种不同浓度的标准溶液和实际样品连续9次进样,峰面积的相对标准偏差小于7%。选取北京市18个区县及全国部分省市的自来水样品进行检测,所得结果令人满意。挑选其中的典型样品进行不同浓度的标准加入实验,回收率在86.7%-119.0%之间。     

Development of trichloroacetic acid sensor based on molecularly imprinted polymer membrane for the screening of complex mixture of haloacetic acids in drinking water

This work shows developing conductometric sensor based on molecularly imprinted polymer (MIP) for the screening of complex mixture of haloacetic acids (HAAs) in drinking water. The recognition of the HAAs was achieved by trichloroacetic acid (TCAA)-imprinted polymers synthesised from the copolymerization of 4-vinylpyridine (4-VPD) and ethylene glycol dimethacrylate (EDMA) in the presence of the TCAA template in acetonitrile, either by bulk polymerization (BP) method or by a multi-step swelling polymerization (MSP) method. TCAA-imprinted polymer of both methods was tested for re-binding with the template and its analogs. It was found that these polymers could bind selectively to the template molecule and HAA derivatives. HAA measurements were carried out by the application of the polyvinyl chloride membrane fabricated with TCAA-imprinted polymer on conductometric sensors. The technological parameters (operating frequency, membrane composition, ionic strength and medium pH) for the sensors were identified and optimised in respect to the response to TCAA, using sensor fabricating with BP-based MIP as a model. The selectivity of the sensors constructed with MIPs made by either that of the two imprinting methods was also investigated, which the influence of the method of imprinting on the binding strength and selectivity of the recognition element embedded in sensor was observed. The sensors showed high sensitivity and selectivity for the response toward TCAA, the sensor modified with MSP-based MIP being better. In addition, the sensors, particularly when was constructed with MSP-based MIP exhibited good cross-reactivities with a wide range of HAAs, which is useful for the screening of the group of HAA usually present in chlorinated water in complex mixtures. Thus, the sensor modified with MSP-based MIP was chosen for analytical application. The calibration of this sensor was determined, showing the good linear graphs (R²>0.970) for HAAs over the concentration range of 25-1000 μg/l and the detection limit of each HAA in the range 0.2-5.0 μg/l. Moreover, the results in real analysis of the sensor indicate the simplicity and reliability of the method. The present work demonstrated that the sensor based on TCAA-imprinted polymer is a fast and sensitive screening method of HAAs in drinking water.     

Determination of haloacetic acids in water using layered double hydroxides as a sorbent in dispersive solid‐phase extraction followed by liquid chromatography with tandem mass spectrometry

In the present study, highly efficient and simple dispersive solid‐phase extraction procedure for the determination of haloacetic acids in water samples has been established. Three different types of layered double hydroxides were synthesized and used as a sorbent in dispersive solid‐phase extraction. Due to the interesting behavior of layered double hydroxides in an acidic medium (pH?4), the analyte elution step was not needed; the layered double hydroxides are simply dissolved in acid immediately after extraction to release the analytes which are then directly introduced into a liquid chromatography with tandem mass spectrometry system for analysis. Several dispersive solid‐phase extraction parameters were optimized to increase the extraction efficiency of haloacetic acids such as temperature, extraction time and pH. Under optimum conditions, good linearity was achieved over the concentration range of 0.05–100 μg/L with detection limits in the range of 0.006–0.05 μg/L. The relative standard deviations were 0.33–3.64% (n = 6). The proposed method was applied to different water samples collected from a drinking water plant to determine the concentrations of haloacetic acids.     

臭氧化对水厂水中消毒副产物生成势的影响

以某饮用水厂沿程工艺出水为研究对象,研究了臭氧化预处理对水体中消毒副产物(DBPs)氯化生成势的影响。结果表明,水厂生物处理单元产生的胞外聚合物(EPS)和溶解性微生物产物(SMP)等生物源有机物是非常有效的DBPs前体物,但其更易于氯化生成三卤甲烷(THMs)而非卤乙酸(HAAs)。水厂水中存在的THMs前体物主要是各类大分子量有机物,并且臭氧工艺对其有较好的氧化去除效果。水厂水中经臭氧氧化产生的小分子量有机物可能是更为有效的一氯乙酸(MCAA)和一溴乙酸(MBAA)前体物。此外,当水体中三氯乙酸(TCAA)前体物浓度较高时,臭氧工艺对TCAA生成势具有很好的去除效果。     

Effect of electrostatic interaction on the adsorption of globular proteins on octacalcium phosphate crystal film

The electrostatic effect on the adsorption of globular proteins, such as bovine serum albumin (BSA), hen egg white lysozyme (LZM), and beta-lactoglobulin (beta-Lg), on octacalcium phosphate (OCP)-like crystal thin films was investigated. A poorly crystalline thin film was synthesized on a tissue culture polystyrene (TCP) surface and used as a model surface in this study. The solution pH clearly affected the electrostatic properties of both proteins and surface. The adsorbed amounts obtained at quasi-steady state were readily related to the solution pH for each protein. The adsorption rate is fast during the initial period and levels off gradually. The maximum adsorbed mass occurred at pH 7 for BSA and at pH 9 for LZM. beta-Lg adsorbed similar amounts at pHs lower than 9, but the adsorbed mass decreased at pHs higher than 9 where electrostatic repulsion exists. The pH values where the maximum adsorbed mass occurred may be considered as the conditions where electrostatic attraction is most favorable. The adsorbed mass of beta-Lg was the greatest among the proteins of interest while BSA adsorbed the least despite its greater molecular mass. LZM falls into the intermediate region. According to these observations, BSA has undergone conformational changes that prevent further adsorption to a greater extent than the others. A simple relationship between the adsorption rate and the electrostatic properties was not established. However, the order of magnitude of the adsorption rate at the initial period tends to be the same as that of maximum adsorbed mass for each protein.     

Analysis of adsorption and binding behaviors of silver nanoparticles onto a pyridyl-terminated surface using XPS and AFM

In this study, we analyzed adsorption and binding behaviors of citrate-capped silver nanoparticles (AgNPs) on a pyridyl-terminated surface using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Adsorption of the AgNPs onto the pyridyl-terminated silicon wafer surface was completed through pH-controlled sol immersion. The adsorption occurred predominantly at a pH less than the pK(b) value of the pyridyl group and more than the pK(a1) of citric acid, indicating that the driving force behind adsorption was electrostatic interaction. Adsorption of citrate onto the pyridyl group also occurred at pK(a1) < pH < pK(b) without AgNPs. According to XPS in the N1s region, larger deprotonation from the pyridinium-formed pyridyl groups was demonstrated subsequent to adsorption of the AgNPs. The deprotonation from the pyridinium indicates the formation of the neutral pyridyl group as the counterpart of hydrogen bonding with the carboxyl group of citrate. The binding state between the pyridyl group and citrate surrounding AgNPs is expected to be kept stable through hydrogen bonding and van der Waals force derived from the AgNPs approach to the pyridyl surface.     

Separation and determination of emetine dithiocarbamate metal complexes by capillary electrophoresis with chemiluminescence detection of the tris(2,2'-bipyridine)-ruthenium(II) complex

A new cellulose-based anion-exchanger was prepared by grafting polyallylamine onto cellulose. The material was obtained by partial oxidation of a size-exclusion grade cellulose gel by aq. NaIO4, forming dialdehyde cellulose, followed by Schiff base formation with a polyallylamine (PAA, molecular mass 5000) and subsequent reduction for stabilization. Three grades of PAA-cellulose gels, with amino group contents of 0.78, 1.01 and 1.28 mmol/g cellulose, were examined for their ionic interaction with mono- and divalent carboxylic acids at pH 2.5-5.5. While the retention factor for monovalent acids was nearly proportional to the amino group content of the gel, that for divalent acids was remarkably greater for the PAA-cellulose gel than for the conventional diethylaminoethyl (DEAE) cellulose gel bearing more amino groups (1.97 mmol/g cellulose). Such high capacity can be explained by the high local density of amino groups on grafted PAA, in contrast to the random and sparse charge distribution in conventional exchangers.     

Simultaneous Determination of Haloacetic Acids in Environmental Waters using Electrospray Ionization Liquid Chromatography Mass Spectrometry

Negative ionization electrospray liquid chromatography mass spectrometry was developed for the simultaneous determination of all nine haloacetic acids containing bromine and chlorine. Haloacetic acids were separated on a crosslinked polystyrene resin column using 3% acetic acid dissolved in acetonitrile:water (20:80) as mobile phase. The precision of this method varied from ±2.2 to ±7.1% for nine haloacetic acids. In addition, quantitative results obtained with spiked water samples at three different concentrations are described. The limit of detection of the proposed method using 200 mL of water samples was between 0.003 and 0.070 μg/L. This method was successfully applied to the trace determination of haloacetic acids in waste water, river water, and seawater.     

Amino acid adsorption on mesoporous materials: influence of types of amino acids, modification of mesoporous materials, and solution conditions

In order to disclose the dominant interfacial interaction between amino acids and ordered mesoporous materials, the adsorption behaviors of five amino acids on four mesoporous materials were investigated in aqueous solutions with adjustable amino acid concentration, ion strength, and pH. The selected amino acids were acidic amino acid glutamic acid (Glu), basic amino acid arginine (Arg), and neutral amino acids phenylalanine (Phe), leucine (Leu), and alanine (Ala), and the selected mesoporous materials were SBA-15, Al-SBA-15, CH3(10%)-SBA-15, and CH3(20%)-SBA-15. The adsorption capacities of Glu and Arg were strongly dependent on pH and surface charge of the mesoporous adsorbent. The adsorption of Phe showed pH insensitivity but depended on the surface organic functionalization of mesoporous adsorbent. On the basis of the theoretical analysis about the interaction between amino acid and adsorbent, such a remarkable difference was attributed to the different nature of the interaction between amino acid and adsorbent. Arg could be readily adsorbed on the surface of SBA-15, especially Al-SBA-15, under appropriate pH in which the electrostatic interaction was predominant. The driving force of Phe adsorption on mesoporous adsorbent mainly came from the hydrophobic interaction. Therefore, the adsorption capability of Arg decreased with increasing ion strength of solution, while the adsorption capability of Phe increased with the increasing degree of CH3 functionalization on SBA-15. For neutral amino acid Phe, Ala, and Leu, the adsorption capability increased with the increase of the length of their side chains, which was another evidence of hydrophobic effect. Thus, all the adsorption of amino acids on mesoporous silica materials can be decided by the combined influence of two fundamental interactions: electrostatic attraction and hydrophobic effect.     

Determination of haloacetic acids in water by ion chromatography--method development.

The microextraction/ion chromatographic (IC) method developed in this study involves extraction of 9 haloacetic acids (HAAs) from aqueous samples (acidified with sulfuric acid to a pH of < 0.5 and amended with copper sulfate pentahydrate and sodium sulfate) with methyl tert-butyl ether (MTBE), back extraction into reagent water, and analysis by IC with conductivity detection. The separation column consists of an Ion Pac AG-11 (2 mm id x 50 mm length) guard column and an Ion Pac AS-11 (2 mm id x 250 mm length) analytical column, and the concentration column is a 4 mm id x 35 mm length Dionex TAC-LP column. Use of the 2 mm id Dionex AS-11 column improved detection limits especially for trichloracetic acid (TCAA), bromodichloroacetic acid (BDCAA), dibromochloroacetic acid (DBCAA), and tribromoacetic acid (TBAA). The peak interfering with BCAA elutes at the same retention time as nitrate; however, we have not confirmed the presence of nitrate. Stability studies indicate that HAAs are stable in water for at least 8 days when preserved with ammonium chloride at 100 mg/L and stored at 4 degrees C in the dark. At day 30, recoveries were still high (e.g., 92.1-106%) for dichloroacetic acid (DCAA), BCAA, dibromoacetic acid (DBAA), trichloroacetic acid (TCAA), BDCAA, and DBCAA. However, recoveries of monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), and TBAA were only 54.6, 56.8, and 66.8%, respectively. Stability studies of HAAs in H2SO4-saturated MTBE indicate that all compounds except TBAA are stable for 48 h when stored at 4 degrees C in the dark. TBAA recoveries dropped to 47.1% after 6 h of storage and no TBAA was detected after 48 h of storage. The method described here is only preliminary and was tested in only one laboratory. Additional research is needed to improve method performance.     

Adsorption Behavior of Amino Acids on a Stainless Steel Surface

The adsorption behavior of various amino acids on a stainless steel surface was investigated at 30 degrees C and over a pH range of 3-10. Acidic and basic amino acids except histidine adsorbed remarkably at pH 3-4 and 7-10, respectively, and showed Langmuir-type adsorption isotherms. The effects of pH and ionic strength on the adsorption isotherms were investigated to analyze the interactions between amino acids and adsorption sites on the stainless steel. Hydrophobic amino acids and glycine showed only small adsorbed amounts at all pHs tested. For the acidic and basic amino acids, reversibility of the absorption and the influence of the ionic strength on the adsorption behavior were examined. The adsorption isotherms of the derivatives of aspartic acid were also measured in order to examine the contribution of the carboxylic groups of acidic amino acids to the adsorption. Furthermore, a Fourier-transform infrared spectroscopic analysis and semiempirical molecular orbital calculation were carried out to analyze the ionization states and the configuration of the amino acids adsorbed on a stainless steel surface. These investigations suggest that the acidic and basic amino acids adsorb through two electrostatic interactions of two ionized groups in the amino acid with a stainless steel surface. Copyright 2000 Academic Press.     

超积累植物李氏禾叶细胞干粉对Cr(VI)的吸附特性研究

借助拟合吸附动力学和等温热力学方程, 研究了湿生超积累植物李氏禾叶细胞干粉对Cr(VI)的吸附性能. 考察了pH值、吸附时间等多种因素对吸附性能的影响; 利用扫描电镜(SEM), X射线能谱(EDS)对李氏禾干粉表面形貌及元素分布进行了表征. 结果表明, 该吸附是单分子吸附的伪二级动力学过程, 吸附过程包含两个步骤: Cr(VI)离子通过静电作用富集在干粉材料表面, 随后干粉表面存在的功能配位官能团会与Cr(VI)发生化学作用. 结合红外光谱图发现对铬起吸附作用的主要是含O, N功能原子的配位官能团, 并且不同功能原子与Cr(VI)的作用方式不同.     

Modeling equilibrium and kinetics of metal uptake by algal biomass in continuous stirred and packed bed adsorbers

Physical and chemical characterization of algae Gelidium particles shows a gel structure, with two major binding groups, carboxylic and hydroxyl groups, with an affinity constant distribution for protons, well described by a Quasi-Gaussian distribution suggested by Sips. A continuous model, considering a heterogeneous distribution of the carboxylic groups, determined by potentiometric titration experiments, was able to predict equilibrium data at different pH. The metal uptake capacity decreases with the solution pH, suggesting that competition exists between hydrogen ions, present in high concentrations for low pH values, and metal ions. For high ionic strengths, adsorption sites will be surrounded by counter ions and partially lose their charge, which weakens the contribution of the electrostatic binding and decreases the overall adsorption. A small influence of the temperature in the adsorption process was observed. Batch kinetic experiments were also performed, at different pH values, and results were well fitted by a mass transfer model, considering the intraparticle diffusion resistance given by the linear driving force model (LDF). Continuous stirred adsorber (CSTA) and packed bed column configurations were also tested for metal adsorption. The biosorbent regeneration was achieved by contacting it with strong acid (0.1 M HNO₃). A mass transfer model was applied with success to describe the biosorption/desorption process in CSTA and packed bed column, considering the equilibrium given by the Langmuir equation/mass action law and film and intraparticle diffusion resistances.     

Specific adsorption of simple organic acids on metal(hydr)oxides: a radiotracer approach

The pH dependence of adsorption of (14)C-labeled benzoic and oxalic acids on gamma-Al(2)O(3) and hematite was studied in acid medium in the presence of 0.5 mol dm(-3) NaClO(4) supporting electrolyte. It was found that the adsorption of the organic species starts at pH values where the protonation of the oxide surface takes place. In the case of benzoic acid the extent of adsorption with decreasing pH goes through a sharp maximum at a pH value not far from the pK (4.2) of the acid, while in the case of oxalic acid only a small decrease can be observed at very low pH values (pH<1). In indirect radiotracer studies using (35)S-labeled sulfate ions it was shown that the competitive adsorption of formic, malonic, maleic, and oxalic acids with sulfate ions depends on pH and the effect of the organic acid on the anion adsorption becomes pronounced at pH values about and above the pK of the acid. On the basis of these observations and considerations concerning the dissociation of the organic acids studied it is assumed that the specific adsorption of the anionic form of the acids takes place. It is, however, emphasized that the negative charge of the anions, consequently the electrostatic forces, do not play significant role in the adsorption.     

Temperature dependence of peptide carboxylic group IR spectra in the amide I′ region at neutral and acidic pH

Analysis of the temperature-dependent amide I′ bands of peptides and proteins can be complicated by their overlap with other IR bands, particularly those of carboxylic groups of amino acid side-chains and the C-terminus. Previously, we reported IR spectra of charged carboxylic side-chains in Asp and Glu amino acids, and C-terminal groups of several amino acids and dipeptides at neutral pH. To complement these results, here we investigate the IR absorptions of Asp and Glu side-chains in capped amino acids (AcAspNMe and AcGluNMe), at both neutral and acidic pH. Spectra of protonated (acidic pH) C-terminal group absorptions are also investigated, using three dipeptides (AlaGly GlyAla and GlyGly) as model compounds. Sets of temperature-dependent experimental IR spectra were analyzed using pseudo-Voigt lineshape profiles. We find that the temperature-dependent behavior of the IR bands of deprotonated (neutral pH) side-chains in AcAspNMe and AcGluNMe dipeptides are generally similar to those reported previously for Asp and Glu. Protonated carboxylic group (acidic pH) IR bands behave uniformly with respect to temperature, showing very similar magnitude frequency shifts and intensity changes. Implications for analyses of amide I′ bands of peptides and proteins are discussed.     

Production of a bioflocculant by Aspergillus parasiticus and its application in dye removal

Aspergillus parasiticus was found to produce a bioflocculant with high flocculating activity for Kaolin suspension and water-soluble dyes. Results showed that the carbon and nitrogen sources favorable for the production of the bioflocculant were corn starch and peptone, and an optimal condition of 28 °C, initial pH 5–6 and shaking speed of 150 rpm. The highest flocculating efficiency achieved for Kaolin suspension was 98.1%, after 72 h cultivation. The bioflocculant was mainly composed of sugar (76.3%) and protein (21.6%), and an average molecular weight of 3.2 × 10⁵ Da. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectra showed that amino, amide and hydroxyl groups were present in the bioflocculant molecules. The bioflocculant was effective in flocculating some soluble anionic dyes in aqueous solution, in particular Reactive Blue 4 and Acid Yellow 25 with a decolorization efficiency of 92.4 and 92.9%, respectively. The decolorization efficiency was dependent on the flocculant dosage and solution pH. XPS result shows that the amine groups in the bioflocculant were protonated at pH 5, and thus the positive bioflocculant was attracted to the negatively charged dye molecules. The amino and amide groups in the bioflocculant molecule are believed to play an important role in flocculation from the viewpoint of electrostatic interaction.