Hydrogel beads based on carboxymethyl cellulose for removal heavy metal ions

Environment‐friendly carboxymethyl cellulose (CMC) hydrogel beads were successfully prepared using epichlorohydrin (ECH) as a crosslinking agent in the suspension of fluid wax. There was an ether linkage formed between ECH and CMC, which was identified from bands in FTIR spectra of the prepared hydrogel. The prepared hydrogel beads with diameters about 4 mm were apparently spherical and fully transparent. The X‐ray diffraction (XRD) spectra indicated that the adsorption of metal ion onto the oxygen atom of carboxyl group led to change in crystallinity patterns of hydrogels. The scanning electron microscope (SEM) images clearly showed that the hydrogels had an internal porous structure. The adsorption capacity increased as initial concentrations of metal ions and the pH value of metal ion solution increased. Freundlich and Langmuir isotherm models were employed to analyze the data from batch adsorption experiments. There are vey good correlation coefficients of linearized equations for Langmuir model, which indicated that the sorption isotherm of the hydrogel beads for metal ions can be fitted to the Langmuir model. The maximum adsorption amount of hydrogel beads for metal ions is 6.49, 4.06, and 5.15 mmol/g for Cu(II), Ni(II), and Pb(II), respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

铁炭微电解法预处理羧甲基纤维素生产废水

采用铁炭微电解法对羧甲基纤维素废水进行预处理试验,研究了初始pH值、曝气、停留时间等关键因素对COD去除的影响。结果表明当进水COD的质量浓度为16000mg/L,进水初始pH值为3.5,停留时间75min,铁炭体积比为1∶1,曝气量为5L/min,此条件下COD去除率为35.14%,试验达到了预期目的。     

Phenol removal from wastewater using eco-friendly hybrid hydrogels

The intent of this study was to evaluate the ability of low-cost polyacrylamide/starch hybrid hydrogels in removing organic pollutants from wastewater, using phenol as a model compound, besides of investigating the adsorption/desorption behavior as a function of hydrogels composition. The results indicated that the hydrogel with the lowest amount of starch and crosslinking agent exhibited the maximum phenol adsorption capacity, 21 mg g⁻¹. The adsorption isotherm data were described by Langmuir and Freundlich adsorption isotherm models. According to linear regression analysis, the Freundlich isotherm model was the best fit among the isotherm models for the adsorption process. Furthermore, desorption study revealed a minimum of about 60% of phenol release, indicating reusability to wastewater treatment.     

Radiation-induced grafting of acrylamide and methacrylic acid individually onto carboxymethyl cellulose for removal of hazardous water pollutants

Carboxymethyl cellulose hydrogels were synthesized by grafting of acrylamide (AAm) and methacrylic acid (MAAc) individually with different concentrations onto carboxymethyl cellulose (CMC) using direct radiation grafting technique. It was found that for both Poly(CMC/AAm) and Poly(CMC/MAAc), the grafting yield and grafting ratio increase with the increasing monomer concentration. Also, it is noted that both grafting ratio and grafting yield of Poly(CMC/AAm) are higher than that of Poly(CMC/MAAc). The effect of different monomer concentrations on gel (%) and swelling behavior was studied. It is found that the increasing monomer concentration increases gel (%). For Poly(CMC/AAm) hydrogels, the swelling behavior decreases with increasing AAm concentration due to high crosslinking hydrogel formation, while as MAAc content increases, swelling behavior increases up to Poly(CMC/MAAc) 1:25 wt%. Swelling kinetics and diffusion mechanism indicate that the water penetration obeys non-Fickian transport mechanism. The structures and properties of the original CMC and the prepared Poly(CMC/MAAc) and Poly(CMC/AAm) were characterized using different analytical tools such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscope (SEM). This study provides a solution to the discharge of different pollutants from wastewater. The adsorption capacity of Poly(CMC/MAAc) and Poly(CMC/AAm) hydrogels toward heavy metals, Cu⁺² and Co⁺², dyes such as acid blue dye and methyl green, and organic contaminants such as 4-chlorophenol and 2,4-Dichlorophenoxy acetic acid has been investigated.     

纤维素乙醇废水处理研究与工程应用

采用铁炭微电解-Fenton+UASB+MBR组合工艺处理纤维素乙醇废水,并对工程设计运行参数和污染物去除机理进行了探索。结果表明:在微电解反应5 h,UASB停留时间36 h,MBR停留时间25 h条件下处理纤维素乙醇废水,经絮凝脱色后出水COD、氨氮等指标均达到《发酵酒精和白酒工业水污染物排放标准》(GB 27631—2011)中的规定,且运行效果稳定,费用较低。     

Treatment of gray wastewater and heavy metal removal from aqueous medium using hydrogels based on novel crosslinkers

Water contamination by heavy metals is a serious environmental problem. Several adsorbents with high adsorption capacity have been reported by researchers. In this paper we report the application of a new crosslinker allyl sorbitol (AS), and two other crosslinkers viz. allyl mannitol (AM) and allyl pentaerythritol (AP), toward the synthesis of polymer hydrogels. These hydrogels have been utilized for the removal of heavy metal ions from water. Chemically crosslinked polyacrylic acid hydrogels have been prepared using these crosslinkers viz. AS or AM or AP. The synthesized crosslinked hydrogels have been utilized for the removal of heavy metal ions from water. The maximum copper (Cu) metal ion removal of 81.8, 81.6, 86.8% and adsorption capacity of 409, 408, 434 mg/g were found with AS, AM and AP crosslinker based hydrogels respectively. While the maximum nickel (Ni) metal ion removal of 96.8, 96.6, 99.0% and adsorption capacity of 484, 483, 495 mg/g were found with AS, AM and AP crosslinkers based hydrogels respectively. The maximum chemical oxygen demand (COD) reduction of 72, 74, 78% and total dissolved solids reduction of 86%, 83%, 95% were found with AS, AM, AP based polymer gel respectively. Approximately, 439.2, 451.4, and 475.8 (mg COD removed/g polymer gel) of pollutants reduction capacity was achieved during their treatment.     

Radiation synthesis of graphene oxide/composite hydrogels and their ability for potential dye adsorption from wastewater

A high yield of graphene oxide (GO) was chemically synthesized from graphite powder utilizing adjusted Hummer's method. The contents of acidic functional groups in GO were determined using potentiometric titration. Composite hydrogels dependent on graphene oxide/poly(2-acrylamido-2-methylpropanesulfonic acid)/polyvinyl alcohol (GO/PAMPS/PVA) were synthesized utilizing a ⁶⁰Co gamma irradiation source at different doses. The synthesized graphene oxide and composite hydrogels were portrayed via X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared analysis. The morphology of composite hydrogels was characterized by scanning electron microscope. The gel % and swelling % for the prepared hydrogel demonstrated that the swelling % of hydrogel increased with raising AMPS content. Whereas the increment of GO and increasing the irradiation dose lead to a reduction in the swelling %. The influences of pH, GO percentage, initial dye concentration, the adsorbent dosage, contact time, and temperature on the adsorption of basic blue 3 dye were evaluated and the adsorption capacity was 194.6 mg/g at optimum conditions; pH = 6, GO/PAMPS/PVA composite hydrogels with 5 wt% of GO, initial dye concentration = 200 mg/L, adsorbent dose = 0.1 g, solution volume = 50 mL after 360 min at room temperature (25°C). The adsorption of dye onto the GO/PAMPS/PVA composite hydrogels follows Pseudo-second-order adsorption kinetics, fits the Freundlich adsorption isotherm model.     

纳米零价铁的制备、改性及对废水中重金属和 有机污染物的去除

纳米零价铁（nZVI）结合了零价铁还原性强和纳米材料比表面积大的特点,能够高效去除水体中的重金属和有机污染物,是当前环境科学领域研究的热点之一。研究表明单一nZVI颗粒存在易团聚及表面易被氧化等问题,影响nZVI颗粒形态和对污染物去除效果,限制了其在环境修复中的应用。针对目前的研究现状,本文分析并总结了以下内容：①nZVI常用的制备方法;②提高nZVI活性与稳定性的改性方法,如合成时添加表面活性剂和负载材料;③nZVI去除废水中Cr、Cd、Cu和As等重金属和硝基苯、氯代芳烃、氯代脂肪烃等有机污染物的主要机理及影响因素;④应用于自然环境中的nZVI可能对环境产生的毒理学效应和在环境修复过程中存在的潜在风险及其评估;⑤对nZVI今后的研究重点和方向进行分析和展望。     

微电解-UASB-接触氧化处理羧甲基纤维素废水

针对羧甲基纤维素(CMC)废水高浓度、高盐分和难生物降解的特点,采用微电解-UASB-生物接触氧化组合工艺处理高浓度CMC废水。废水含盐约4%,COD和BOD5分别约20000mg.L-1和2100mg.L-1。最佳条件下微电解对COD去除率为35%,处理后废水B/C提高到0.34,稀释后经UASB和两级接触氧化法对COD的去除率分别达到了80%、75%和65%,最终出水COD在100mg.L-1以下,达到国家一级排放标准。通过GS-MS和颗粒污泥分析,分别研究了微电解对污染物去除特性和去除机理与UASB的启动特性。微电解-UASB-生物接触氧化组合技术具有运行稳定、高效和抗冲击等优点。     

膨润土/羧甲基纤维素钠水凝胶的制备及其应用

通过化学交联技术制备了一种生态友好和成本低廉的BT-g-CMC水凝胶，并对其结构和形貌进行了表征，并将其用于废水中回收磷和缓释磷肥。吸附研究表明，当CMC/BT的质量比值为1时，在298 K下水凝胶对H2PO4-具有良好的亲和力，吸附容量为18.78 mg/g，吸附平衡时间为120 min；其次，将富含磷的BT-g-CMC1.0水凝胶用作缓释肥料（SRFs），结果表明，SRFs具有优良的保水和缓释能力。盆栽实验表明，SRFs对蔬菜生长具有促进作用。土壤修复实验表明，当SRFs用量为0.3g，浸出3次时，对土壤中Cr(Ⅲ)的固定化率为82.9%。因此，SRFs具有广泛的工业和绿色农业应用。     

活性氧化镁处理含铬废水的研究

研究了菱镁矿焙烧制备的活性氧化镁作为吸附剂从溶液中去除六价铬,考察了氧化镁的用量、初始pH及吸附反应温度对处理效果的影响。实验结果表明：活性氧化镁对六价铬离子具有较强的吸附能力,随着氧化镁投加量的增加六价铬离子去除率达到99.5%;升高温度对反应的促进作用不大;pH一般在偏中性条件下容易使吸附反应达到更为理想的效果。反应后的氧化镁焙烧后吸附性能几乎没有下降,可多次反复利用。     

Radiation synthesis and characterization of 2‐hydroxyethyl‐methacrylate‐based hydrogels containing di‐ and tri‐protic acid and its application on wastewater treatment

Radiation‐crosslinked 2‐hydroxyethylmethacrylate/citric acid (HEMA/CAc), 2‐hydroxyethylmethacrylate/tartaric acid (HEMA/TA), and 2‐hydroxyethylmethacrylate/succinic acid (HEMA/Sc) copolymers were prepared by using ⁶⁰Co γ‐rays. The gel fraction yield and the swelling behavior of the prepared hydrogels were studied. It was shown that increasing irradiation doses was accompanied by an increase in yield of gel fraction and a decrease in swelling degree. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, swelling exponent, and diffusion coefficient of the hydrogels were determined by studying the swelling behavior of the hydrogels prepared. It was seen that the equilibrium swelling degree increases as the content of acid increases, as a result of introducing more hydrophilic groups. When the hydrophilic polymer (acids) varies in the content range of 40–80 mg, swelling exponents (n) decreases, thereby indicating a shift in the water‐transport mechanism from the anomalous (non‐Fickian)‐type to the Fickian‐type. Characterization and some selected properties of the prepared hydrogels were studied, and accordingly the possibility of its practical use in the treatment of industrial wastes such as dyes and heavy metals (Fe, Ni, Co, and Cu) were also studied. The effect of treatment time, pH of feed solution, initial feed concentration, and temperature on the dye and heavy metals uptake was determined. The uptake order for a given metal was HEMA/TA hydrogel > HEMA/CAc > HEMA/Sc hydrogel. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Micellar solutions of amphipathic copolymers based on carboxymethyl cellulose

A novel family of amphipathic copolymers based on carboxymethyl cellulose (CM‐cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM‐cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first‐order autocorrelation function g⁽¹⁾(τ) of a copolymer of CM‐cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single‐exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30–100 nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size. © 2003 Society of Chemical Industry     

废水中砷、锑污染物的去除方法研究进展

综述了废水中砷、锑污染物的处理方法、作用机理,及各类去除方法的优势和不足。同时探讨了铁盐类的新型水处理药剂高铁酸盐在去除废水中砷、锑复合污染物方面的优势。最后对废水中砷、锑污染物的去除方法及进展提出展望,以期为后续研究提供参考。     

pH-response of chitosan, κ-carrageenan, carboxymethyl cellulose sodium salt complex hydrogels

We synthesized the polyelectrolyte complex hydrogel consisting of chitosan, κ-carrageenan, and carboxymethyl cellulose sodium salt (NaCMC) and investigated the swelling properties of the gel varying with carrageenan/NaCMC compositions. In a lower composition of carrageenan, heterogeneous gels were obtained indicating strong electrostatic interactions among these polyelectrolytes. Oppositely, in a higher composition of carrageenan, a gelation did not occur. It was cleared that a homogeneity of the gel strongly depended on the carrageenan/NaCMC composition. The degree of swelling at the equilibrium decreased proportional to the carrageenan composition. The gels showed a maximum degree of swelling in the range of pH 11-12. The maximum degree of swelling discontinuously decreased with increasing the NaCMC composition and was independent of the composition at a higher composition of NaCMC. Swelling properties in pure water and in alkaline solutions were also affected by salt concentrations of each polyelectrolyte aqueous solutions.     

Adsorption removal of Brilliant green and Safranin-O contaminants from water using a hydrogel based on carboxymethyl cellulose and sodium alginate crosslinked by epichlorohydrin

The current study investigates the adsorption properties of a chemically crosslinked hydrogel based on sodium alginate (NaALG) and carboxymethyl cellulose (CMC). The structural characteristics of the investigated hydrogel are described using information from Fourier Transform–infrared spectra, X-ray diffraction patterns and field emission scanning electron microscopy pictures. The NaALG/epichlorohydrin (ECH)/CMC hydrogel was synthesised under optimised conditions with respect to the swelling percentage. Various reaction parameters were varied to obtain the maximum swelling percentage. The synthesised hydrogel was taken as an adsorbent in the decolorisation of Brilliant green (BG) and Safranin-O (SO) dyes from water. According to the kinetic investigations, the decolorisation equilibrium of SO by NaALG/ECH/CMC was discovered in 4 hours (98.98%), while the removal of BG by NaALG/ECH/CMC took 6 hours (97.7%). Chemical processes were used to describe the decolorisation mechanisms, which significantly supported the pseudo-first-order model. NaALG/ECH/CMC hydrogel absorption was indicated to take place in monolayer adsorption form (Langmuir isotherm). The highest adsorption capacity for BG was discovered to be 864.8 mg g⁻¹ and for SO it was 193.1 mg g⁻¹, by synthesised hydrogel, where “mg” refers to the commercial colourant and not to the pure dye. Therefore, the synthesised hydrogel can be considered as a smart device for the adsorption of dye in water purification tasks.     

糠醛渣制备羧甲基纤维素的研究

以糠醛渣为原料,采用Milox法提取纤维素,经漂白处理后制备羧甲基纤维素(CMC),对纤维素提取工艺、漂白工艺及CMC的合成进行了初步研究。实验结果表明,纤维素提取工艺优化条件:甲酸80mL,过氧化氢14mL,反应时间2.5h—2.5h—2.5h,反应温度80℃—95℃—80℃;漂白工艺条件:可选择过氧化氢10mL,氢氧化钠质量浓度2.5g/L,反应温度45℃,反应时间60min。制得的CMC的取代度为0.901 2,黏度为45mPa·s。