Nanotechnology‐based wastewater treatment

Water contamination is a global challenge impacting both the environment and human health with significant economic and social costs. The growing scarcity of usable water resources requires effective treatment of wastewater. In this context, developing cheaper, safer and more efficient wastewater treatment technologies are the need of the hour. One promising approach that several studies have reported success has been the usage of nanomaterials in water and waste water management. The rapid progress of research in nanomaterial sciences has shown their growing potential; however, there has not been a great amount of information available on their implementation. This review focuses on developments in nanotechnology that hold strong potential for wastewater treatment. The review covers key techniques in nanomaterial‐based water treatments including adsorption, filtration and photocatalysis with recent examples showing how to improve their properties and efficiencies according to the need.     

Catalytic conversion of MTBE to biodegradable chemicals in contaminated water

The behavior of different acid zeolites in the hydrolysis at room temperature of methyl tert-butyl ether (MTBE) was studied with reference to the possibility of its conversion to more biodegradable products in underground water contaminated by MTBE. The effect of the structure of the zeolite and SiO₂/Al₂O₃ ratio was analyzed. The results indicate that acid H-MFI and H-BEA zeolites are effective in both adsorption and hydrolysis of MTBE and may be applied for both in situ underground water remediation and as protection barrier for wells or leaking tanks. However, other zeolites (mordenite and faujasite) result completely inactive. Furthermore, contrary to what was expected, the increase of the Si/Al ratio promotes the reactivity which is determined by the resistance to diffusion of MTBE in the pores of zeolites and the resistance of back-diffusion of the reaction products.     

对氨基苯甲酸生产废水的树脂吸附预处理

采用超高交联吸附树脂处理芳香两性化合物对氨基苯甲酸(PABA)生产废水,通过静态吸附、动态吸附-脱附实验,研究确定了最佳的吸附-脱附工艺条件。结果表明,在常温和2 BV/h的吸附流量条件下,原废水不用调节pH值,直接经JX-101树脂吸附处理20 BV后,CODC r可从6 000 mg/L左右降至700 mg/L左右,CODC r去除率达88%以上,PABA的吸附去除率达99%以上。采用1 BV 8%氨水溶液 1 BV 4%氨水溶液 2 BV水作脱附剂,在313 K脱附温度和1 BV/h脱附流量的条件下,树脂脱附性能良好。该工艺简单,运行稳定,操作简便,可回收有用物质,有望实现工业化。     

Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

天然气脱汞吸附剂的制备及其性能评价

天然气中含汞会对天然气的开发及使用带来危害，实验采用固定床吸附法脱除天然气中的汞。实验以Al₂O₃和活性炭复合颗粒为载体，通过浸渍法负载S、CuS和CuS _x 多组分活性物，制备了天然气脱汞吸附剂，考察了制备工艺条件的影响。采用X射线衍射检测（XRD）与扫描电镜（SEM）对活性物负载情况进行了表征。结果表明，在载体上成功负载了CuS和S，其中CuS质量分数为12.80%，总S质量分数为8.32%。以含汞空气模拟含汞天然气，考察了进气口汞含量、停留时间对脱汞吸附剂脱汞效果的影响。结果表明，脱汞剂处理汞含量为300μg/m³的天然气，停留时间为1s时，出口汞含量为24.99μg/m³，已达到工业天然气要求。当停留时间为2s、进气口汞含量达到600μg/m³时，经脱汞剂脱汞后，出口汞含量为18.92μg/m³，达到小于28μg/m³要求。脱汞吸附剂的汞容量达到6.36%。     

Superparamagnetic polyvinylpyrrolidone/chitosan/Fe3O4 electrospun nanofibers as effective U(VI) adsorbents

Magnetoactive electrospun fibrous membranes consisting of polyvinylpyrrolidone (PVP), chitosan (CS) and pre-fabricated, double-layer oleic acid-coated magnetite nanoparticles (OA.OA.Fe₃O₄) were fabricated and evaluated as new adsorbent materials for the removal and recovery of uranium (U(VI)) from aqueous solutions. The adsorption has been investigated by batch-type experiments and the solid material has been characterized by X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and vibration sample magnetometry (VSM) measurements prior and after uranium adsorption. The experimental adsorption data were found to be well fitted with the Langmuir isotherm and the pseudo-second order kinetic model. The results indicate that PVP/CS/OA.OA.Fe₃O₄ fibrous adsorbents exhibit good adsorption properties towards U(VI) in aqueous solutions, achieving a q_max value of 0.77 mol kg⁻¹ (183.3 mg g⁻¹) at pH 6.0. The experiments regarding the regeneration and reuse of the magnetoactive adsorbents were carried out using Na₂CO₃, at pH ~11. After four cycles, the percentage relative adsorption remained stable (~100%) whereas the desorption percentage decreased from 31.9% to 21.0%. Generally, the presented results demonstrate that the incorporation of the Fe₃O₄ NPs has a positive effect on the adsorption efficiency of U(VI) from aquatic environments.     

基于13X沸石分子筛/MgCl_2的复合吸附剂性能实验研究

复合吸附剂的吸附性能是吸附制冷循环过程中的一个重要参数,基于测试整体成型复合吸附剂吸附性能的需要,本文设计搭建了一种整体成型吸附剂性能测试装置,对复合吸附剂MgCl_2-13X进行了吸附性能测试实验。结果表明:该实验装置中吸附床外侧底部的温度变化速率较接近吸附床内部底部吸附剂的温度变化速率,二者温度变化速率相差0.01~1.9℃/min,整个吸附和脱附过程二者温度的平均值相差约3.24%,能够满足吸附剂性能测试实验的要求。吸附剂性能测试实验及电镜下吸附剂的微观结构表明:浸泡法制备的复合吸附剂的吸附性能与MgCl_2溶液的浓度有关,MgCl_2能够改善13X沸石分子筛的吸附性能,本实验测得当MgCl_2溶液的浓度为15%时所制得复合吸附剂MX3性能最优,其最大吸附量为0.32 g/g,最大吸附速率0.59 g/min,相比单一吸附剂13X沸石分子筛提高了20%。     

农业废弃物作为吸附剂去除水中重金属研究

农业废弃物主要由纤维素和木质素组成,是一种潜在的重金属吸附剂。文中归纳了几种农业废弃物吸附剂及其改性方法,阐述了改性农业废弃物吸附重金属的机理,讨论了pH、重金属离子初始浓度、吸附剂用量、反应温度等因素对改性农业废弃物吸附能力的影响,并展望了改性农业废弃物的应用前景。     

Dye‐affinity hollow‐fibres and their lysozyme adsorption–desorption characteristics

Dye‐affinity adsorption is increasingly used for protein separation. Hollow‐fibres have advantages as adsorbents in comparison to conventional bead supports because they are not compressible and can eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow‐fibres to which Reactive Green HE‐4BD was attached for adsorption of lysozyme. The hollow‐fibre was characterized by scanning electron microscopy. These dye‐carrying hollow‐fibres (26.3 µmol g^?1) were used in the lysozyme adsorption–elution studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye‐attached hollow‐fibres was studied in a batch system. The non‐specific adsorption of lysozyme on the polyamide hollow‐fibres was 1.8 mg g^?1. Reactive Green HE‐4BD attachment significantly increased the lysozyme adsorption up to 41.1 mg g^?1. Langmuir adsorption model was found to be applicable in interpreting lead adsorption by Reactive Green HE‐4BD attached hollow fibres. Significant amount of the adsorbed lysozyme (up to 95%) was eluted in 1 h in the elution medium containing 1.0 M NaSCN at pH 8.0. In order to determine the effects of adsorption conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We concluded that polyamide dye‐affinity hollow‐fibres can be applied for lysozyme adsorption without causing any significant conformational changes. Repeated adsorption–elution processes showed that these dye‐attached hollow‐fibres are suitable for lysozyme adsorption. © 2001 Society of Chemical Industry     

污泥含炭吸附剂的制备工艺优化及性能表征

采用先活化剂浸泡活化在干燥热解炭化的化学活化法制备污泥含炭吸附剂.实验结果表明,有机污泥在活化温度为450℃、ZnCl2药剂和干泥质量比为0.7:1、活化时间为1.5 h、锯末添加剂投加量为2%的条件下,制得的含炭吸附剂碘值在510 mg/g以上,收率>60%,比表面积>390 m2/g.由扫描电镜观察可见孔径分布以微孔和中孔为主.