Investigation of municipal and olive mill wastewater co‐treatment in activated sludge–powdered activated carbon (AS‐PAC) systems

BACKGROUND: The purpose of this study was to investigate the co‐treatment of olive‐mill wastewater (OMW) and municipal wastewater in activated sludge systems operating in the absence and presence of different adsorbent materials and to study the role of sorption and biodegradation in total phenols removal. RESULTS: Batch experiments were initially conducted to investigate total phenols' adsorption capacity on activated sludge (AS), olive pomace (OP) and powdered activated carbon (PAC). According to the results, PAC presented the best adsorption capacity. Three sequencing batch reactors (SBRs) were also operated, treating municipal wastewater and different amounts of OMW. The first SBR contained AS (AS‐System), the second AS and OP (AS‐OP System) and the third AS and PAC (AS‐PAC System). All SBRs operated sufficiently in the presence of 1% v/v OMW, achieving mean COD and total phenols removal efficiency higher than 86% and 85%, respectively, and satisfactory settling capacity. Increase of OMW concentration to 5% v/v affected the performance of SBRs, resulting in mean COD removal efficiencies that ranged between 61% (AS‐OP System) and 80% (AS‐PAC System). CONCLUSION: Among the SBRs used, the AS‐PAC System operated with highest performance in the presence of 1 and 2.5% v/v OMW, and showed better stability in the presence of 5% v/v OMW. Calculation of total phenols mass flux revealed that biodegradation was the principal mechanism of their removal. The highest values of mean biotransformation rates were calculated for the AS‐PAC System and ranged between 2.0 and 40.6 d^?1 for different experimental phases. Copyright © 2012 Society of Chemical Industry     

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。     

Polyethyleneimine‐grafted membranes for simultaneously adsorbing heavy metal ions and rejecting suspended particles in wastewater

Heavy metal ions (HMIs) in wastewater can be removed by polyethyleneimine (PEI) adsorption, however, it is difficult to recycle PEI macromolecules from their mixture with suspended particles in wastewater. A novel HMIs adsorption technique with renewable PEI‐grafted porous membranes was developed. PEI molecules were dispersed with high specific area and structured morphology, which allowed HMIs and suspended particles to be retained separately at different locations of the membrane, with the former adsorbed in matrix and the latter rejected on surface. The membranes with the optimized PEI loading ratio of 30 k wt % behaved excellently with microsphere rejection and Co(II) adsorption reaching 98.5% and 51.0 mg/g, respectively. They successfully decreased Co(II) concentration from 3.0 mg/L to the allowable discharge standard (0.5 mg/L), even with an enhanced flux of 6200 L/m²/h at 0.12 MPa under the cyclic tests. Overall, PEI‐grafted membrane adsorption is highly efficient for removing HMIs and suspended particles simultaneously from wastewater. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4541–4548, 2017     

Acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐ methylpropane sulfonic acid‐based hydrogels: Synthesis,characterization and their application in the removal of heavy metals

Crosslinked acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐methylpropane sulfonic acid (AN/AAx/AMPS)‐based hydrogels were prepared by free radical crosslinking solution polymerization technique. The chemical structures of the hydrogels were characterized by FT‐IR analysis. The morphology of the dry hydrogel sample was examined by scanning electron microscope (SEM). These hydrogels were used for the removal of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was arranged in the order of Cd(II) > Fe(III) > Cu(II). It was observed that the specific interaction between metal ions and ionic comonomer in the hydrogel affected the metal binding capacity of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Simultaneous removal of Cd,Co, Cu,Mn, Ni and Zn from synthetic solutions on a hemp‐based felt: Experimental design

The potential of using a hemp‐based material in felt form as an adsorbent for removing the metals from aqueous mixtures of Cd, Co, Cu, Mn, Ni, and Zn is investigated in the present study using batch experiments at an initial pH between 4.9 and 5.2. The operating variables studied were initial metal concentration, adsorbent dosage, contact time, agitation speed, temperature, presence of NaCl, and pH. Experiments showed that this nonconventional adsorbent exhibited interesting capacities: 1 g of hemp was able to remove 7.4 mg of metals at a concentration of 25 mg/L for each metal present in 100 mL of solution. Kinetic results showed that the process was uniform and rapid: adsorption of metals reached equilibrium in 10 min. The adsorption capacities were almost independent of temperature between 25 and 50 °C and pH between 4 and 6, but dependent on the presence of electrolytes such as NaCl. Interesting results were also obtained for real polymetallic effluents. All these findings are significant for the future development of hemp‐based materials for use as bag filters for metal removal from industrial effluents. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44422.     

Supported photocatalysis as a pre‐treatment prior to biological degradation for the removal of some dyes from aqueous solutions; Acid Red 183, Biebrich Scarlet,Methyl Red Sodium Salt,Orange II

BACKGROUND: The aim of this study was to assess the feasibility of coupling photocatalysis and a biological treatment for the removal of azo dyes from aqueous effluents. Biological processes do not always appear relevant for dyes removal, owing to the low or total absence of biodegradability of this class of pollutants. RESULTS: During photocatalysis pre‐treatment, a decrease in the chemical oxygen demand (COD) indicated oxidation of the target compound and thus a change in the chemical structure; better biodegradability or less toxicity could then be expected. However, the concomitant decrease in dissolved organic carbon (DOC), characteristic of a high mineralization yield, led to nearly constant COD:DOC ratios, which was unfavorable for an increase in biodegradability. It was confirmed by the low values found for the ratios biological oxygen demand (BOD₅) to COD, which remained in the range 0.09–0.19, namely below 0.4 after photocatalytic reaction. Moreover, toxicity increased or remained at a high level after irradiation of the azo dyes for 3 h, and decreased only for Orange II, from toxic (EC₅₀ = 53%) to moderately toxic (EC₅₀ = 76%). CONCLUSION: An integrated process involving photocataysis and biological treatment to treat azo dyes appeared unsuitable under the conditions tested and may only be considered for Orange II among the four dyes tested. Copyright © 2010 Society of Chemical Industry     

Study on the synthesis of a macroporous ethylacrylate‐divinylbenzene copolymer,its conversion into a bi‐functional cation exchange resin and applications for extraction of toxic heavy metals from wastewater

Macroporus ethylacrylate‐divinylbenzene copolymers were synthesized by suspension polymerization using diethyl phthalate and n‐heptane as diluent. A hydrolysis study revealed that conversion of esters into carboxylic acid groups was dependent on three factors: (1) crosslinkage: increases with a decrease in crosslinkage, (2) reagent: sulfuric acid>aqueous NaOH>NaOH in a 1 : 1 water to ethylene glycol, and (3) pore volume (PV): highest when PV was ～ 0.7 mL g^?1. Sulfuric acid hydrolyzed ester to ? COOH and introduced ? SO₃H on phenyl rings, thus producing a bi‐functional resin. The functional groups were verified by IR spectroscopy and quantified by acid–base titration. The bi‐functional resin's capacity for toxic heavy metals in water samples was 12.51, 10.43, 9.43, 13.21, and 11.12 mg g^?1 for Cu, Cd, Ni, Pb, and Zn, respectively and the recoveries exceeded >95% in range of pH 2–8, showing that it is suitable for water purification. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dye removal from colored‐textile wastewater using chitosan‐PPI dendrimer hybrid as a biopolymer: Optimization,kinetic, and isotherm studies

Preparation of a biopolymer chitosan‐polypropylene imine (CS‐PPI) as a biocompatible adsorbent and its reactive textile dyes removal potential were performed. Chemical specifications of CS‐PPI were determined using Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR. The surface morphology of the CS‐PPI surface was characterized by scanning electron microscopy. Results confirmed that the linkages between the NH₂ groups of PPI dendrimer and carboxylic groups of modified Chitosan were accomplished chemically. Two textile reactive dyes, reactive black 5 (RB5) and reactive red 198 (RR198), were used as model compounds. A response surface methodology was applied to estimate the simple and combined effects of the operating variables, including pH, dye concentration, time contact, and temperature. Under the optimal values of process parameters, the dye removal performance of 97 and 99% was achieved for RB5 and RR198, respectively. Furthermore, the isotherm and kinetic models of dyes adsorption were performed. Adsorption data represented that both examined dye followed the Langmuir isotherm. The adsorption kinetics of both reactive dyes were satisfied by pseudo‐second order equation. Based on this study, CS‐PPI due to having high adsorption capacity (6250 mg/g for RB5 and 5882.35 mg/g for RR198), biocompatibility and ecofriendly properties might be a suitable adsorbent for removal of reactive dyes from colored solutions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013