The removal of bisphenol A by hollow fiber microfiltration membrane

The removal of bisphenol A (BPA) from drinking water by hollow fiber microfiltration (MF) membrane using dead-end model was investigated. The experiment was focused on the effect of various factors including BPA initial concentration, pH, ionic strength and organic matter on removal efficiency. Adsorption plays a significant role in BPA removal in MF filtration. The results showed that MF could remove BPA effectively. A higher removal was obtained at the beginning of the filtration, and the removal efficiency decreased to around 20% when the membrane became saturated due to adsorption of BPA onto the MF membrane. As pH of solution approached to pKa (9.6-11.3) of BPA, BPA removal efficiency dropped significantly. The effect of ionic strength on BPA removal was negligible. The presence of natural organic matter (NOM) demonstrated no observable impact on BPA removal. After filtration, the backwash could recover removal efficiency effectively.     

纤维膜聚结脱除双酚A反应液中残留的游离酸

研究了纤维膜聚结技术用于脱除双酚A反应液中残留游离酸的实验条件和纤维膜床层的再生条件。结果表明,在聚结温度70 ℃、95%乙醇用量2%、空速20～30 h－1、纤维膜床层体积1.0 cm3的条件下,可使双酚A反应液的酸度从0.014 mmol/L脱除至≤0.001mmol/L,满足双酚A反应液对酸度的要求;当双酚A反应液的处理量达到纤维膜床层体积的60倍时,床层必须采用丙酮进行再生;在丙酮用量6 mL和再生温度50 ℃的条件下,纤维膜床层可以得到完全再生。     

Use of chitosan for removal of bisphenol A and bisphenol derivatives through tyrosinase‐catalyzed quinone oxidation

In this study, the availability of chitosan was systematically investigated for removal of bisphenol A (BPA, 2,2‐bis(hydroxyphenyl)propane) through the tyrosinase‐catalyzed quinone oxidation and subsequent quinone adsorption on chitosan beads. In particular, the process parameters, such as the hydrogen peroxide (H₂O₂)‐to‐BPA ratio, pH value, temperature, and tyrosinase dose, were discussed in detail for the enzymatic quinone oxidation. Tyrosinase‐catalyzed quinone oxidation of BPA was effectively enhanced by adding H₂O₂ and the optimum conditions for BPA at 0.3 mM were determined to be pH 7.0 and 40°C in the presence of H₂O₂ at 0.3 mM ([H₂O₂]/[BPA] = 1.0). Removal of BPA from aqueous solutions was accomplished by adsorption of enzymatically generated quinone derivatives on chitosan beads. The use of chitosan in the form of beads was found to be more effective because heterogeneous removal of BPA with chitosan beads was much faster than homogeneous removal of BPA with chitosan solutions, and the removal efficiency was enhanced by increasing the amount of chitosan beads dispersed in the BPA solutions and BPA was completely removed by quinone adsorption in the presence of chitosan beads more than 0.10 cm³/cm³. In addition, a variety of bisphenol derivatives were completely or effectively removed by the procedure constructed in this study, although the enzyme dose or the amount of chitosan beads was further increased as necessary for some of the bisphenol derivatives used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Flat-plate submerged membrane bioreactor for the treatment of higher-load graywater

Graywater treatment has been the focus when topics of decentralized treatment systems are discussed. In this paper, the treatment of higher-load graywater, a mixture of washing machine and kitchen sink wastewater, was investigated. A 10 L lab-scale submerged membrane bioreactor (subMBR) was operated with a flat-plate membrane for 87 days. Permeate was intermittently withdrawn at constant transmembrane pressure (TMP) induced by water level difference and without pump requirement. The pollutants' removal and membrane behavior were monitored. The COD removal was around 96% and a permeate COD of about 26 mg L^− 1 was obtained. The total linear alkylbenzene sulfonate (LAS) removal achieved was > 99%, indicative of its non-inhibited degradation even at influent concentration of 30.8 mg L^− 1. The subMBR was operated at almost stable and constant flux of 0.22 m³ m^− 2 d^− 1 at a mean HRT of 13.6 h.     

浸没式膜生物反应器膜污染研究现状

简要分析了浸没式膜生物反应器(SMBR)中膜污染的机理.在文献和现场考察的基础上,对膜材料、混合液特性、操作参数与条件、膜的清洗与再生等几个主要方面的研究现状进行了分析和综述,指出目前研究的不足在于缺乏反应器结构优化及反应器内流场优化方面的研究.     

A study on submerged rotating MBR for wastewater treatment and membrane cleaning

A submerged rotating membrane bioreactor (SRMBR), with a rotatable, rounded, flat-sheet Poly(vinyldiene fluoride) (PVDF) membrane module fixed on hollow axes and moved by an electromotor, was used for wastewater reclamation. It was found that the effluent COD became stable and lower than 20 mg/L after one day running. The equilibrium permeate flux increased from 42.5 to 47.5 L/m²·h with the rotation speed increasing from 15 r/min to 25 r/min. Prolonging relaxation time could alleviate membrane fouling and enhance the flux. Finally, membrane cleaning was studied. The results showed that flushing the membrane surface with water, water/NaOH and water/NaOH/HCl recovered permeate flux to 48.4%, 83.5% and 90.2% of that of the initial operation, respectively.     

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

Layer-by-layer assembly is a versatile technique for fabricating nanofiltration membranes, where multiple layers of polyelectrolytes are usually required to achieve reasonable separation performance. In this work, an ionic strength directed self-assembly procedure is described for the preparation of nanofiltration membranes consisting of only a single bilayer of poly(diallyldimethylammoniumchloride) and poly(sodium-4-styrenesulfoate). The influence of background ionic strength as well as membrane substrate properties on the formation of single-bilayer membranes are systematically evaluated. Such a simplified polyelectrolyte deposition procedure results in membranes having outstanding separation performance with permeating flux of 14.2 ± 1.5 L∙m^–2∙h^–1∙bar^–1 and Na₂SO₄ rejection of 97.1% ± 0.8% under a low applied pressure of 1 bar. These results surpass the ones for conventional multilayered polyelectrolyte membranes. This work encompasses an investigation of ionic strength induced coiling of the polyelectrolyte chains and emphasizes the interplay between-polyelectrolyte chain configuration and substrate pore profile. It thus introduces a new concept on the control of membrane fabrication process toward high performance nanofiltration.     

A comparison of hydrodynamic methods for mitigating particle fouling in submerged membrane filtration

Hydrodynamic methods are used for mitigating particle fouling and for enhancing the filtrate flux in submerged membrane filtration. In the comparison membrane blocking-cake formation filtration system, the effects of filtration pressure, aeration intensity, backwash duration and stepwise increasing pressure on the filtration resistances and filtration flux are measured and discussed. Aeration is helpful for reducing particle deposition on the membrane surface, while stepwise increasing pressure can mainly mitigate internal fouling of the membrane. Periodic backwash can significantly reduce both the resistance caused by the membrane internal fouling and by cake formation; consequently, it can effectively recover the filtrate flux. In contrast, increasing the pressure in constant pressure filtration leads the flux to be decreased due to more severe membrane blockage. According to the comparison of the long-term flux and the received filtrate volume, among these hydrodynamic methods, the periodic backwash with longer duration is the optimal strategy for the filtration.     

A comparison of submerged and sidestream tubular membrane bioreactor configurations

This paper provides an improved understanding of the effect of sidestream (SS) and submerged (Sub) MBR configurations on hydraulic and biological system performance for a tubular membrane geometry. Effects of key flow parameters, these being aeration rate (U_G) in the Sub MBR and cross flow velocity (CFV) in the SS MBR, on fouling behaviour have been assessed during short-term flux-step experiments. Both synthetic and real sewage feeds have been used. Series of tests carried out with both feeds indicate the similar fouling behaviour observed for Sub and SS MBRs operated at U_G of 0.07-0.11 m s⁻¹ and CFV of 0.25-0.55 m s⁻¹ respectively. Analysis of the TMP-based parameters determined from the flux-step experiments show the effect of U_G in Sub configuration to be greater than those of CFV in SS MBR, and to be more efficient at higher fluxes (up to 97% decrease in fouling rate for U_G increased from 0.02 to 0.2 m s⁻¹, at 291 m⁻² h⁻¹). The influence of MBR configuration on biomass characteristics was also assessed by acclimatising the biomass at three MLSS concentrations for both configurations and revealed the carbohydrate contained in the biomass supernatant to be a possible indicator of fouling for MBR operation.     

旋转薄膜浆态光催化反应器

在分析现有光催化反应器特点的基础上,提出了一种新型的旋转薄膜式浆态光催化反应器（RFFS）。用商品化光催化剂Degussa P25,以苯酚模型有机物为降解对象,对比了RFFS与传统鼓泡浆态光催化反应器（TBS）的性能,研究了RFFS的光催化性能。结果表明,与传统浆态光催化反应器相比,RFFS具有较高的光催化性能,尤其是能够在较高的光催化剂浓度下运行。在光催化体系的循环流速大于2.7 L·min-1、供气流量为1.0 L·min-1、催化剂浓度为3.0 g·L-1的条件下,RFFS比传统浆态鼓泡光催化反应器的降解速率提高1.6倍。RFFS利用旋转浆态薄膜强化了光催化反应体系的传质,同时提高了体系中光催化剂对光能的利用率,较好地解决了光在传统浆态体系中的传递问题,为开发新型的具有工业应用前景的光催化反应器提供了方案。苯酚在RFFS中的降解动力学符合表观一级动力学模型,理论值与实验结果吻合较好。     

Comparison with as-grown and microwave modified carbon nanotubes to removal aqueous bisphenol A

This study utilized carbon nanotubes (CNTs) to remove bisphenol A (BPA) from aqueous solution. The surfaces of CNTs were modified by SOCl₂/NH₄OH under microwave irradiation. The surface characteristics of as-grown and modified CNTs were analyzed by measuring zeta potential, and using a scanning electron microscope, a surface area analyzer and a Fourier transform infrared spectroscope. The specific surface area of modified CNTs exceeded that of as-grown CNTs. The pH_iep values of as-grown CNTs and modified CNTs were determined to be 4.3 and 6.5, respectively. Some amine functionalities were formed on the surface of modified CNTs; therefore, the surface of the modified CNTs contained more positive charges than that of the as-grown CNTs. The adsorption kinetics were examined using pseudo first- and second-order models, intraparticle diffusion and Bangham's models. The equilibrium data were simulated using Langmuir, Freundlich, Dubinin and Radushkevich (D-R) and Temkin isotherms. The results reveal that the pseudo second-order model and Langmuir isotherm fit the kinetics and equilibrium data, respectively. The adsorption capacity of BPA on the surface of CNTs fluctuates very little with pH in the range of 3-9, suggesting the high stability of CNTs as an adsorbent for BPA over a rather wide pH range. The values of ΔH⁰ and ΔS⁰ were calculated to be − 11.7 kJ/mol and 46.1 J/mol, respectively. The isotherm and thermodynamic simulations indicate that the adsorption of BPA onto as-grown CNTs proceeds by physisorption process.     

一体式膜生物反应器中料液粘度的研究

探讨了一体式膜生物反应器中料液粘度变化的原因,以及料液粘度对膜过滤阻力的影响。试验结果表明:料液粘度的增加主要因反应器中累积的高浓度胞外聚合物(EPS)所致;污泥粘度随着EPS浓度的变化而变化,二者之间存在很好的相关性(r=0.9958);污泥粘度与膜过滤阻力有较好的相关性(r=0.9006)。     

膜法脱硝技术的应用

介绍膜法脱硝技术在新疆中泰化学（集团）股份有限公司的分公司阜康能源有限公司循环经济项目中的应用情况,重点分析了该技术运行中出现的问题,并提出了改进措施。     

腐殖酸对Al~0-O_2体系去除双酚A的影响

在酸性条件下,采用Al0-O2体系去除双酚A(BPA),考察了腐殖酸(HA)对Al0-O2体系中BPA的去除、H2O2原位生成和pH值变化的影响,探讨了其影响机理。试验结果表明,Al0-O2体系可以有效地去除水中BPA,加入HA可以促进Al0-O2体系去除BPA。HA抑制Al0-O2体系中H2O2原位生成,HA的投加量越大,抑制作用越明显;但HA可以促进H2O2转化为.OH。后者的促进作用强于前者的抑制作用,使得整体反应表现为HA促进BPA的去除。     

Optimization of photooxidative removal of p-nitrophenol in a spinning disc photoreactor using response surface methodology

In this article, response surface methodology (RSM) was used to obtain optimum conditions for removal of p-nitrophenol (PNP) by UV/H₂O₂ process using spinning disk photoreactor (SDP). For this purpose, the effect of five independent variables, the initial concentration of PNP, the initial concentration of H₂O₂, pH, solution volume, and irradiation time on the PNP removal percent, was investigated. Central composite design, one of the response surface techniques used for process optimization. The results showed a good agreement between the RSM predicted and experimental data with “R²” and “Adjusted R²” of 0.9692 and 0.9480, respectively. In addition, “Predicted R²” of 0.8909 is in reasonable agreement with “Adjusted R²” of 0.9488. At optimal conditions, that is, PNP concentration of 20.78?mg L^?1, H₂O₂ concentration of 1355.83?mg L^?1, solution volume of 566.08?mL, irradiation time of 12.30?min, and pH of 4.59 the removal percent predicted by RSM is 100% which has good correspondence with its experimental value (98.67%).     

A low pressure SWCNT-ENM sandwich membrane system for the removal of PPCPs from water

While carbon nanotubes are known as efficient adsorbents for removal of a number of contaminants from water, the possibility of their leaching into drinking water has prevented their application in water treatment. In this study, single walled carbon nanotubes (SWCNT) were sandwiched between two electrospun nanofibre membranes (ENM). The relatively small pore size of the ENM prevented the mechanically entangled nanotubes from passing through and contaminating the water. The performance of the SWCNT-ENM was evaluated in a lab-scale setup for the removal of PPCPs. For this purpose, a feed solution spiked with known concentrations of six PPCPs was passed through the membrane system. The target substances included acetaminophen (ACT), bezafibrate (BZF), iopromide (IOP), diclofenac (DCF), carbamazepine (CBZ), and sulphamethoxazole (SMX). The same test was also conducted using a single contaminant (ACT). Results demonstrated a decrease in the overall percent removal of PPCPs as feed flow rate and PPCP concentration increased. For multi-component feeds containing equal amounts of the aforementioned PPCPs, the overall percent removal decreased from 90.8% to 71.0% when increasing the feed concentration from 30 to 600 μg/L. Experiments using sandwiched powdered activated carbon (PAC) showed that the dynamic adsorption capacity of PPCPs by SWCNT-ENM was higher than that of PAC-ENM, and remained unaffected by the feed composition. In addition, the high porosity of this novel membrane allowed for flow of water with low resistance such that the trans-membrane pressure was found to be as low as 4 kPa at a pure water flux of 330 L/m²h.     

Hybrid sorbent-ultrafiltration systems for fluoride removal from water

Fluoride contaminated water sources are found in many parts of the world and the consumption of such water is causing dental and skeletal fluorosis in humans, especially in developing countries. Hybrid sorbent-ultrafiltration (UF) systems are proposed for the removal of fluoride from water for the first time in this study. Laterite and bone char were selected as they are low cost, accessible sorbents in developing countries. The performances of the laterite-UF and bone char-UF systems were compared in terms of fluoride removal and membrane permeability under varying fluoride concentration, solution pH, and sorbent load. For equilibrium fluoride concentration of 1.5 mg/L, the World Health Organization guideline for safe drinking water, the sorption capacity of bone char (1.1 mg/g) was larger than that of laterite (0.40 mg/g) and this was attributed to the larger surface area of bone char. For the laterite-UF system, increase in fluoride concentration resulted in a decline in UF permeability whereas for the bone char-UF system there was no influence of fluoride concentration on membrane permeability. The optimal solution pH at which the systems are operated at maximum sorption capacity while avoiding membrane fouling was determined as pH 5-6 for the laterite-UF and pH 7 for the bone char-UF system. For both systems, the permeability declined in a similar manner as the sorbent load increased. Although both systems require further optimization, they showed to be viable defluoridation technologies.     

A novel photoreactor for the production of electrosterically stabilised colloidal particles at larger scales

A novel photoreactor to facilitate electrosteric stabilization of colloidal polymer particles is presented. Anionic and cationic polystyrene particles having a diameter of ca. 100 nm and bearing a thin layer of photoinitiator are used as seed colloids. Anionic and cationic chains of weak or strong polyelectrolytes are grafted onto the surface of these particles. The polyelectrolyte chains are densely tethered onto the surface of the polymer particles. For this purpose, a commercial photoreactor setup developed for water and liquid waste treatment has been adapted. Compared to the photoreactor used earlier for photoemulsion polymerization, the new reactor largely shortens the reaction times and improves the reproducibility of the reaction. This is achieved by the higher UV power and controlled radiation times and power.