吸附法去除废水中重金属研究进展

重金属污染问题已经成为近年来危害最大的水污染问题之一。各种有效去除水体中的重金属的处理技术与方法受到了世界各国政府和研究者们的极大关注。釆用吸附技术来处理含重金属的废水是一种非常有效和具有发展前景的方法之一。本文介绍了重金属水污染的现状与危害,废水处理中去除重金属常用的吸附剂。     

Superior adsorption performance of graphitic carbon nitride nanosheets for both cationic and anionic heavy metals from wastewater

Water pollution caused by highly toxic Cd(II), Pb(II), and Cr(VI) is a serious problem. In the present work,a green and low-cost adsorbent of g-C_3N_4 nanosheets was developed with superior capacity for both cationic and anionic heavy metals. The adsorbent was easily fabricated through one-step calcination of guanidine hydrochloride with thickness less than 1.6 nm and specific surface area of 111.2 m~2·g~(-1). Kinetic and isotherm studies suggest that the adsorption is an endothermic chemisorption process, occurring on the energetically heterogeneous surface based on a hybrid mechanism of multilayer and monolayer adsorption. The tri-s-triazine units and surface N-containing groups of g-C_3N_4 nanosheets are proposed to be responsible for the adsorption process.Further study on pH demonstrates that electrostatic interaction plays an important role. The maximum adsorption capacity of Cd(II), Pb(II), and Cr(VI) on g-C_3N_4 nanosheets is 123.205 mg·g~(-1), 136.571 mg·g~(-1),and 684.451 mg·g~(-1), respectively. The better adsorption performance of the adsorbent than that of the recently reported nanomaterials and low-cost adsorbents proves its great application potential in the removal of heavy metal contaminants from wastewater. The present paper developed a promising adsorbent which will certainly find applications in wastewater treatment and also provides guiding significance in designing adsorption processes.     

废水重金属的生物吸附研究进展

生物吸附法是目前处理重金属废水的一种行之有效的方法,特别是对于低浓度废水,其优势明显,还可达到以废治废的目的。对废水重金属的生物吸附进行了综述,详细介绍了目前最具代表性的四种生物吸附机理以及已经开发出来的五种吸附工艺,同时还探讨了影响生物吸附重金属的多种因素和生物吸附剂的类型,展望了生物吸附废水中重金属在工业生产中的应用前景。     

Adsorption of Cd and Cr ions from industrial wastewater using Ca doped Ni–Zn nanoferrites: Synthesis,characterization and isotherm analysis

Removal of heavy metals (Cd and Cr) from industrial wastewater by adsorption onto a series of Ca substituted nickel zinc nanoferrites (Ca_xNi_0.4Zn_0.6-xFe₂O₄ (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6)) (CNZNFs) was studied in detail. The effect of calcium doping and contact time over adsorption of cadmium and chromium ions was investigated and maximum uptake of Cd (98.25%) and Cr (51%) ions were marked by prepared nanoadsorbents. Structural studies confirmed the formation of spinel structured nanoparticles with crystallite size ranging from 24 to 38 nm while porosity was observed to vary from 52% to 58% with calcium concentration. Pseudo second order (PSO) kinetic model for adsorption of both heavy metals (cadmium and chromium) was observed to be better fitted with adsorption data. Maximum adsorption efficiencies for Cd (128.20 mg/g) and Cr (23.54 mg/g) were found by the data fit of Langmuir isotherm model. Additionally, the adsorption data was found to obey Langmuir isotherm model for both heavy metals due to higher values of correlation coefficients (R² = 0.94131 for cadmium and 0.91091 for chromium) than Freundlich isotherm model (R² = 0.5865 for cadmium and 0.4599 for chromium).     

Tertiary treatment of a secondary effluent by the coupling of coagulation-adsorption-ultrafiltration for reuse

We considered the treatment of secondary effluent by coagulation-adsorption coupled with ultrafiltration. Tests were performed on the secondary effluent of the wastewater treatment plant at Staoueli (Algeria) where the average chemical oxygen demand (COD) was 46 (mg O₂/L) and turbidity, 16 NTU. The ultrafiltration tests were made with mineral tubular CARBOSEP membranes — M5 (10 kg/ mol), M2 (15 kg/mol) — in the dynamic mode with a transmembrane pressure ΔP = 1 bar and cross flow velocity = 3 m/s. The reagents were calcium chloride (as coagulant agent) and powder activated carbon. Coagulation improved the ultrafiltration performances significantly. In the first step, the optimal conditions for coagulation were determined considering the best elimination of turbidity as well as organic matter. In the second step, the efficiency of different processes (coagulation, adsorption, ultrafiltration) was compared when used alone or in combination. The coagulation test showed a COD elimination equal to 12 mg/L at pH = 6.5 for a concentration of CaCl₂ = 50 mg/L and a turbidity equal to 3 NTU.     

膜法处理腈纶厂废水

本文主要研究了用聚砜超滤膜对腈纶厂热牵伸废水、水洗机废水处理回用以及用超滤膜及反渗透膜处理腈纶厂污水的情况。并从工艺可行性上作了探讨。同时，本文还对用膜法处理脯纶厂永经济效益作了估算。     

Adsorption of Pb2+ on Chitosan Cross‐Linked with Triethylene‐Tetramine

A novel triethylene‐tetramine cross‐linked chitosan (CCTS) was synthesized via the cross‐linking of triethylene‐tetramine and epichlorohydrin activated chitosan. Its structure was characterized by elemental analysis, infrared spectroscopy and X‐ray diffraction analysis, and the surface topography was determined with ESEM. The results were in agreement with expectations. The capacity of CCTS to adsorb Pb²⁺ ions from aqueous solutions was examined, and equilibrium and kinetic investigations were undertaken. The adsorption isotherms were fitted well by the Langmuir equation (R > 0.999). The maximum adsorbed amount, at pH 5.5, with an initial concentration of 3 mmol/L (621 ppm), was 378.8 mg/g. The adsorption process could be best described by a second‐order equation (R = 1). This suggests that the rate‐limiting step may be the chemical adsorption (chemisorption) step and not the mass transport. The separation factor used was 0 < R_L < 1. Therefore, it can be concluded that CCTS is an effective adsorbent for the collection of Pb²⁺.     

Integration of Ultrafiltration Unit Operations in Biotechnology Process Design

A stepwise process design approach is proposed to model membrane unit operations generally in combination with experimental model parameter determination in laboratory scale, in order to predict the purification performance a priori by simulations for multicomponent mixtures. The development of a rigorous model for an ultrafiltration membrane is described. In conceptual process design, the degree of comprehension of all unit operations integrated have to be almost identical to be able of any consistent process proposal taking equipment‐related fluid‐dynamical and kinetic nonidealities besides thermodynamical feasibility into account. Therefore, a process model, combining the most limiting factors within one mathematical model, is established and various filtrations are carried out with a binary solution for validation. Additionally, a standard laboratory equipment is instituted for logging time‐dependent concentration profiles. The practicability of the proposed procedure is proven in order to design and integrate ultrafiltration membranes into total purification processes.     

Survey of MBR market: Trends and perspectives in China

Membrane bioreactor (MBR) has gained considerable attention for wastewater treatment and reuse in China in the last two decades. Comparing with the global MBR market, which has an average annual growth rate of 10.9%, the average annual growth rate in China is nearly 100% in recent years. In the past 10 years, publications on MBR researches and applications for wastewater treatment have increased sharply. Over three hundred MBR plants have been successfully applied into practice for different wastewater treatments, such as municipal wastewater, bathing wastewater, restaurant wastewater, landfill leachate, hospital wastewater, petrochemical wastewater and high-concentration industrial wastewater. These plants have capacities ranging from 10 to 100,000 m³/d, among which over 12 MBR plants have capacities exceeding 10,000 m³/d. The largest MBR plant, i.e. Beijing Kunyu River WWPT, which has a capacity of 100,000 m³/d for municipal wastewater treatment and reuse, was constructed in Beijing by Origin Water Technology Co., Ltd. The largest MBR plant for industrial wastewater treatment was located in Tianjin and installed by Motimo Membrane Inc., which has a capacity of 30,000 m³/d. The largest MBR application for industrial sectors was petrochemical wastewater treatment, and over ten MBR plants each exceed a capacity of 5000 m³/d. In South-east China, the constructed MBRs are mostly involved in the high-strength industrial wastewater treatment while in North China MBRs mainly focused on municipal wastewater treatment and reuse.For an MBR commercial application in China, MBR plants were constructed by a lot of home-grown companies such as Tianjin Motimo Membrane Technology Co., Ltd., Beijing Origin Water Technology Co., Ltd. and Omexell Environmental Engineering Co., Ltd. and overseas-funded companies like Zenon-GE and CNC-Simens. Origin Water occupies the majority of the MBR market in China, whereas CNC-Simens and Zenon-GE have a larger number of installations in other parts of China. MBR unit key suppliers in China are Zenon (Canada), Mitsubishi-Rayon (Japan), Toray (Japan), Kubota (Japan), Norit (Netherlands), Motimo (China) etc.Due to more stringent regulations and wastewater reuse strategies, it is expected that a significant increase in MBR plant capacity and a widening of application areas will occur in the future.     

Material‐Auswahlbox zur Herstellung fortgeschrittener Polymermembranen für die Wasseraufbereitung

Within the framework of the MABMEM research project, new high‐performance membranes are being developed for sustainable water management. The performance of the membranes will be evaluated in comparative and standardized fouling tests as well as in terms of the removal of trace impurities on a laboratory scale. Seven candidates are currently being tested in demonstrator trials with real‐water matrix in a waterworks for the direct treatment of dam water without prior coagulation over a period of 6 months. Subsequently, the new membrane materials will be operated with the effluent of a wastewater treatment plant.     

层状复合氢氧化物的结构调控及其吸附重金属离子的研究进展

层状复合氢氧化物（LDHs）是具有特殊层状结构的阴离子黏土,具有化学组成可调、比表面积大及结构记忆效应独特等性质,在废水处理方面备受关注。调控LDHs自身结构,是进一步扩大其应用范围、提高其吸附性能的有效途径。该文介绍了LDHs特殊的层状结构和其自身性质;总结了LDHs最常用的制备方法,即共沉淀法、离子交换法、尿素水解法、煅烧复原法和溶胶-凝胶法等,分别介绍了各种制备方法的原理和特点;综述了LDHs的结构调控对其吸附重金属离子性能的影响,并总结了LDHs对重金属离子的吸附机理;最后,指出了目前LDHs在处理含有重金属离子废水研究中面临的挑战,并对该材料未来的研究方向和发展趋势进行了展望。     

Synthesis of a carbamide-based dithiocarbamate chelator for the removal of heavy metal ions from aqueous solutions

This study was carried out to develop a carbamide-based dithiocarbamate (CDTC) chelator for the removal of heavy metal ions from wastewater. Its structural properties were characterized by FT-IR, ¹H NMR and ¹³C NMR. Results confirmed the functional groups of HNC(S)S existed. The adsorption isotherms showed CDTC had a high adsorption capability for Zn (119.8 mg/g) and Cu (63.1 mg/g). It exhibited a distinctive selectivity for the removal of metal ions (Cu²⁺ > Zn²⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺) as they coexisted. The influence of initial pH of wastewater for the removal efficiency of metal ions was also investigated and a pH > 7 was preferred.     

Optimizing the coagulant dose to control membrane fouling in combined coagulation/ultrafiltration systems for textile wastewater reclamation

Optimal coagulation conditions need to be re-examined when coagulation is coupled to membrane filtration for wastewater treatment. This work focused on the optimization of coagulant dosing in order to control membrane fouling in ultrafiltration (UF), following coagulation for the reclamation of textile wastewater. The effects of pore size and coagulant types and dosages on flux decline were investigated using a stirred-cell UF unit. The flux was greatly enhanced for the UF membrane when a coagulant was added, whereas for the microfiltration (MF) membrane the flux decreased. This could be attributed to changes in the size of coagulated particles and their interaction with membrane pores. At a low dosage (e.g., 0.0371 mM as Al), the polyaluminum chloride (PACl) coagulant was found to control the flux decline most effectively for low ionic-strength wastewater. The optimal dose minimized the fouling and cake layer resistances, although it was sharp and dependent on influent composition. The cake layer protected the membrane from fouling, but it provided additional resistance to permeation. Analyses of turbidity, particle size, and membrane surface exhibited the characteristics of coagulated particles and their cake structures that are closely associated with flux behavior.     

Treating dye wastewater by an integrated process of adsorption using activated carbon and ultrafiltration

The investigation was undertaken to evaluate the effectiveness of using activated carbon (AC) in conjunction with ultrafiltration (UF) in the removal of methylene blue (MB) from aqueous solutions. The combination of activated carbon with UF in this work was to exploit the high adsorption capabilities of AC and the particle removal ability of UF simultaneously. The process was experimentally investigated using granulated and commercial powder-activated carbons. Experiments were conducted in order to study the effects of carbon type, carbon dose, and operating pressure on the process performance. The results obtained showed that the combined process achieved better rejection of dye than the OF process. Furthermore, powder-activated carbons were more effective than the granulated type.