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  • 1.
    Abromaitis, V.
    et al.
    Kaunas Univ Technol, Lithuania ; Wetsus, European Ctr Excellence Sustainable Water Technol, Netherlands.
    Racys, V.
    Kaunas Univ Technol, Lithuania.
    van der Marel, P.
    WLN, Netherlands.
    Ni, Gaofeng
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Wolthuizen, A. L.
    Wageningen Univ, Netherlands.
    Meulepas, R. J. W.
    Wetsus, European Ctr Excellence Sustainable Water Technol, Netherlands.
    Effect of shear stress and carbon surface roughness on bioregeneration and performance of suspended versus attached biomass in metoprolol-loaded biological activated carbon systems2017In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 317, p. 503-511Article in journal (Refereed)
    Abstract [en]

    The bioregeneration of activated carbon (AC) in biological activated carbon (BAC) systems is limited by sorption-desorption hysteresis and transport between the adsorbent and biomass. In this study, we investigated these limitations and whether a biofilm covering the AC surface is required. Consequently, BAC reactors were operated at different shear stress and AC surface smoothness, since this may affect biofilm formation. The experiments were carried out in BAC and blank reactors treating synthetic wastewater containing the pharmaceutical metoprolol. After start-up, all reactors removed metoprolol completely; however, after 840 h the removal dropped due to saturation of the AC. In the blank reactors, the removal dropped to 0% while in the BAC reactors removal recovered to >99%, due to increased biological activity. During the initial phase, the metoprolol was adsorbed, rather than biodegraded. At the end, the AC from the BAC reactors had higher pore volume and sorption capacity than from the blank reactors, showing that the AC had been bioregenerated. At high shear (G = 25 s(-1)), the rough AC granules (R-a = 13 mu m) were covered with a 50-400 gm thick biofilm and the total protein content of the biofilm was 2.6 mg/gAC, while at lower shear (G = 8.8 s(-1)) the rough AC granules were only partly covered. The biofilm formation at lower shear (G = 8.8 s(-1)) on smooth AC granules (R-a = 1.6 mu m) was negligible. However, due to the presence of suspended biomass the reactor performance or bioregeneration were not reduced. This showed that direct contact between the AC and biomass was not essential in mixed BAC systems. The microbial analyses of the suspended biomass and the biofilm on AC surface indicated that metoprolol was mainly biodegraded in suspension. (C) 2017 Elsevier B.V. All rights reserved.

  • 2.
    Bhatnagar, Amit
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Hogland, William
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Marques, Marcia
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Univ Estado Rio De Janeiro, Dept Sanit & Environm Engn, UERJ, Rio De Janeiro, Brazil.
    Sillanpaa, Mika
    Lappeenranta Univ Technol, Fac Technol, FI-50100 Mikkeli, Finland.
    An overview of the modification methods of activated carbon for its water treatment applications2013In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 219, p. 499-511Article, review/survey (Refereed)
    Abstract [en]

    Activated carbon has been recognized as one of the oldest and widely used adsorbent for the water and wastewater treatment for removing organic and inorganic pollutants. The application of activated carbon in adsorption process is mainly depends on the surface chemistry and pore structure of porous carbons. The method of activation and the nature of precursor used greatly influences surface functional groups and pore structure of the activated carbon. Therefore, the main focus of researchers is to develop or modifies the activation/treatment techniques in an optimal manner using appropriate precursors for specific pollutants. In recent years, emphasis is given to prepare the surface modified carbons using different procedures to enhance the potential of activated carbon for specific contaminants. Various methods such as, acid treatment, base treatment, impregnation treatment, ozone treatment, surfactant treatment, plasma treatment and microwave treatment have been studied to develop surface modified activated carbons. In this paper, these modification methods have been reviewed and the potential of surface modified activated carbons towards water treatment has been discussed. This review article is aimed at providing precise information on efforts made by various researchers in the field of surface modification of activated carbon for water pollution control. (C) 2012 Elsevier B.V. All rights reserved.

  • 3.
    Bhatnagar, Amit
    et al.
    LSRE—Laboratory of Separation and Reaction Engineering, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto (FEUP), Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
    Kumar, Eva
    LSRE—Laboratory of Separation and Reaction Engineering, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto (FEUP), Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
    Sillanpää, Mika
    Faculty of Technology, Lappeenranta University of Technology, Patteristonkatu 1, FI-50100, Mikkeli, Finland.
    Fluoride removal from water by adsorption: A review2011In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 171, no 3, p. 811-840Article in journal (Refereed)
    Abstract [en]

    Fluoride contamination in drinking water due to natural and anthropogenic activities has been recognized as one of the major problems worldwide imposing a serious threat to human health. Among several treatment technologies applied for fluoride removal, adsorption process has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. In this review, an extensive list of various adsorbents from literature has been compiled and their adsorption capacities under various conditions (pH, initial fluoride concentration, temperature, contact time, adsorbent surface charge, etc.) for fluoride removal as available in the literature are presented along with highlighting and discussing the key advancement on the preparation of novel adsorbents tested so far for fluoride removal. It is evident from the literature survey that various adsorbents have shown good potential for the removal of fluoride. However, still there is a need to find out the practical utility of such developed adsorbents on a commercial scale, leading to the improvement of pollution control.

  • 4.
    Bhatnagar, Amit
    et al.
    FEUP, Dept Engn Quim, LSRE, P-4200465 Oporto, Portugal & Tech Univ Hamburg, Inst Environm Technol & Energy Econ, D-21073 Hamburg, Germany .
    Kumar, Eva
    FEUP, Dept Engn Quim.
    Sillanpää, Mika
    Univ Eastern Finland.
    Nitrate removal from water by nano-alumina: Characterization and sorption studies2010In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 163, no 3, p. 317-323Article in journal (Refereed)
    Abstract [en]

    The present study was conducted to evaluate the feasibility of nano-alumina for nitrate removal from aqueous solutions. The nature and morphology of sorbent was characterized by XRD, FTIR, BET and SEM analysis. Batch adsorption studies were performed as a function of contact time, initial nitrate concentration, temperature, pH and influence of other interfering anions. Nitrate sorption kinetics was well fitted by pseudo-second-order kinetic model. The maximum sorption capacity of nano-alumina for nitrate removal was found to be ca. 4.0 mg g(-1) at 25 +/- 2 degrees C. Maximum nitrate removal occurred at equilibrium pH ca. 4.4. The nitrate sorption has been well explained using Langmuir isotherm model. Results from this study demonstrated the potential utility of nano-alumina for nitrate removal from water.

  • 5.
    Bhatnagar, Amit
    et al.
    Environmental Science and Technology Division, Central Building Research Institute (CBRI), Roorkee 247667, India.
    Minocha, A.K.
    Utilization of industrial waste for cadmium removal from water and immobilization in cement2009In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 150, p. 145-151Article in journal (Refereed)
    Abstract [en]

    The present study investigates the adsorption potential of metal sludge (a waste product of the electroplating industry) for the removal of cadmium from water. The adsorption capacity of the waste sludge for cadmium was ca. 40 mg g−1 at 25 °C. The adsorption was studied as a function of contact time, concentration and temperature by batch experiments. The adsorption has been found to be endothermic and data conform to the Langmuir model. The analysis of kinetic data indicates that the present adsorption system followed pseudo-first-order kinetics. After the adsorption studies, the metal-laden sludge adsorbent was immobilized in cement for its ultimate disposal. Physical properties such as initial and final setting time and the compressive strength of cement-stabilized wastes were tested to investigate the effect of the metal-laden sludge. The results of the present study clearly reveal that waste metal sludge can be used beneficially in treating industrial effluents containing cadmium and safely disposed of by immobilizing into cement. The proposed technology provides a two-fold advantage of wastewater treatment and solid waste management.

  • 6. Bhatnagar, Amit
    et al.
    Minocha, A.K.
    Pudasainee, D.
    Chung, H.K.
    Kim, S.H.
    Kim, HS
    Lee, G.H.
    Min, B.
    Jeon, B.H.
    Vanadium removal from water by waste metal sludge and cement immobilization2008In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 144, p. 197-204Article in journal (Refereed)
  • 7.
    Bhatnagar, Amit
    et al.
    University of Porto, Portugal.
    Sillanpää, Mika
    Lappeenranta University of Technology, Finland.
    A review of emerging adsorbents for nitrate removal from water2011In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 168, no 2, p. 493-504Article in journal (Refereed)
    Abstract [en]

    Nitrate, due to its high water solubility, is possibly the most widespread groundwater contaminant in the world, imposing a serious threat to human health and contributing to eutrophication. Among several treatment technologies applied for nitrate removal, adsorption has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. In this review, an extensive list of various sorbents from the literature has been compiled and their adsorption capacities for nitrate removal as available in the literature are presented along with highlighting and discussing the key advancement on the preparation of novel adsorbents tested for nitrate removal.

  • 8.
    Bhatnagar, Amit
    et al.
    Tech Univ Hamburg, Inst Environm Technol & Energy Econ, D-21073 Hamburg, Germany & Univ Kuopio, LAEC, Dept Environm Sci, FI-50100 Mikkeli, Finland .
    Sillanpää, Mika
    Utilization of agro-industrial and municipal waste materials as potential adsorbents for water treatment- A Review2010In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 157, no 2-3, p. 277-296Article in journal (Refereed)
    Abstract [en]

    Adsorption process has been proven one of the best water treatment technologies around the world and activated carbon is undoubtedly considered as universal adsorbent for the removal of diverse types of pollutants from water. However, widespread use of commercial activated carbon is sometimes restricted due to its higher costs. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of waste materials as low-cost adsorbents is attractive due to their contribution in the reduction of costs for waste disposal, therefore contributing to environmental protection. In this review, an extensive list of low-cost adsorbents (prepared by utilizing different types of waste materials) from vast literature has been compiled and their adsorption capacities for various aquatic pollutants as available in the literature are presented. It is evident from the literature survey that various low-cost adsorbents have shown good potential for the removal of various aquatic pollutants. However, there are few issues and drawbacks on the use of low-cost adsorbents in water treatment that have been discussed in this paper. Additionally, more research is needed to find the practical utility of low-cost adsorbents on commercial scale.

  • 9.
    Bhatnagar, Amit
    et al.
    Univ Porto, Fac Engn, LSRE, Lab Separat & React Engn,Associate Lab LSRE LCM, P-4200465 Oporto, Portugal .
    Vilar, V.J.P.
    Ferreira, C
    Botelho, C.M.S.
    Boaventura, R.A.R.
    Optimization of nickel biosorption by chemically modified brown macroalgae (Pelvetia canaliculata)2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 193, p. 256-266Article in journal (Refereed)
    Abstract [en]

    In the present work, various forms of algae Pelvetia canaliculata were prepared by different chemical modifications, in order to get the best form of algae for the maximum uptake of nickel. Potentiometric titration revealed that the carboxyl groups were more abundant (3.9 mmol/g) as compared to hydroxyl groups (2.0 mmol/g) on the biosorbent surface. Fourier transform infrared (FUR) analysis of algae was done to identify the role of different functional groups present on algae surface during nickel biosorption. The protonated algae showed least sorption of nickel suggesting that after acid treatment, some of the binding sites were destroyed. Among the various forms of prepared algae. Na-algae prepared directly from raw algae (without protonation) showed highest uptake of nickel. The release of sodium ions during the uptake of nickel ions has shown that the current biosorption mechanism involves ion-exchange being a stoichiometrical ratio of 2:1 between sodium and nickel ions.

  • 10.
    Bhatnagar, Amit
    et al.
    Univ Porto, LSRE, Associate Lab LSRE LCM, Fac Engn, P-4200465 Oporto, Portugal.
    Vilar, V.J.P
    Santos, JC
    Botelho, C.M.S
    Boaventura, R.A.R
    Valorisation of marine Pelvetia canaliculata Ochrophyta for separation and recovery of nickel from water: equilibrium and kinetics modeling on Na-loaded algae2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 200, p. 365-372Article in journal (Refereed)
    Abstract [en]

    In the present study, biosorption of Ni2+ by Na-loaded (raw algae treated with NaCl), algae Pelvetia canaliculata Ochrophyta, was studied in a batch system. Kinetics and equilibrium experiments were conducted at different pH values (2.0, 3.0 and 4.0). The metal uptake capacity decreased by decreasing the solution pH, suggesting that competition exists between hydrogen ions, present in high concentrations at low pH values, and metal ions. An ion-exchange model, considering two different binding sites, sulfonic and carboxylic groups, was developed to describe equilibrium data. A mass transfer model, considering intraparticle resistance was also developed to describe kinetics in a batch system. The release of sodium ions during the uptake of nickel ions revealed that the biosorption mechanism involved ion-exchange between sodium and nickel ions with a stoichiometrical ratio of 2:1. Nickel showed higher affinity to the sulfonic groups than for carboxylic ones of algae biomass. Kinetic results show that hydrogen ions diffuse faster as compared to nickel and sodium ions. The maximum uptake capacity of Na-loaded algae, P. canaliculata, for Ni2+ was found to be ca. 100 mg/g at pH 4.0.

  • 11.
    Brandin, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Hulteberg, Christian
    Lund University.
    Odenbrand, Ingemar
    Lund University.
    High-temperature and high concentration SCR of NO with NH3: application in a CCS process for removal of carbon dioxide2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 191, p. 218-227Article in journal (Refereed)
    Abstract [en]

    This study investigates several commercial selective catalytic reduction (SCR) catalysts (A–E) for application in a high-temperature (approximately 525 °C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NOx seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by measurement in a fixed-bed reactor at 300–525 °C. All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amount of catalyst needed varied considerably and was much higher for the zeolithic materials. The formation of N2O increased with temperature for almost all materials except the zeolithic ones. The selectivity to N2 production at 525 °C was 98.6% for the best material and 95.7% for the worst with 1000 ppm NOx in the inlet; at 5000 ppm NOx, the values were much better, i.e., 98.3 and 99.9%, respectively.

  • 12. Kousha, M.
    et al.
    Daneshvar, E.
    Dopeikar, H
    Taghavi, D.
    Bhatnagar, Amit
    Univ Porto FEUP, Dept Engn Quim, LSRE, Fac Engn, P-4200465 Oporto, Portugal.
    Box-Behnken Design Optimization of Acid Black 1 Dye Biosorption by different Brown Macroalgae2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 179, p. 158-168Article in journal (Refereed)
    Abstract [en]

    Response surface methodology (RSM) based on three-variable-three-level Box-Behnken design was employed to interpret the adsorption characteristics of Acid Black 1 (AB1) dye onto three brown macroalgae viz., Nizamuddin zanardini, Sargassum glaucescens and Stoechospermum marginatum. The effects of three independent variables, viz. biomass dosage, dye concentration, and initial solution pH were studied for the removal of AB1 dye by the three macroalgae. A second-order polynomial model successfully described the effects of independent variables on the AB1 dye removal. The maximum experimental dye removal efficiency of 99.27, 98.12 and 97.62% for N. zanardini, S. glaucescens and S. marginatum, respectively, was obtained, which was in agreement with the calculated values. The results of the present study suggest that these macroalgae can be used as an efficient biosorbents for dye removal from aqueous solution.

  • 13. Kousha, M.
    et al.
    Daneshvar, E.
    Sohrabi, M.S.
    Jokar, M.
    Bhatnagar, Amit
    FEUP, LSRE, Dept Engn Quim, P-4200465 Oporto, Portugal .
    Adsorption of acid orange II dye by raw and chemically modified brown macroalga Stoechospermum marginatum2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 192, p. 67-76Article in journal (Refereed)
    Abstract [en]

    The adsorption of acid orange II (AO7) dye from aqueous solution was examined onto untreated and chemically modified forms (treated with (i) propylamine, (ii) acidic methanol, (iii) formaldehyde and (iv) formic acid with formaldehyde) of brown alga, Stoechospermum marginatum. The adsorption was studied as a function of initial solution pH (2.0-10.0), initial dye concentration (30-90 mg/L), contact time (5-60 min) and biomass dosage (0.2-2.2 g/L) at constant temperature and agitation speed. The kinetic data were well described with the pseudo-second-order model. The results revealed that amine functional groups were mainly responsible for the adsorption of acid orange II dye. The modification of biomass with propylamination enhanced the dye adsorption capacity about two times of the untreated algal biomass. These findings were confirmed by Fourier transform infrared (FT-IR) spectroscopy.

  • 14.
    Kumar, Anuj
    et al.
    Natural Resources Institute Finland (Luke), Finland.
    Ryparová, Pavla
    Czech Technical University in Prague, Czech Republic.
    Hosseinpourpia, Reza
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Prošek, Zdeněk
    Czech Technical University in Prague, Czech Republic.
    Žigone, Jure
    Czech Technical University in Prague, Czech Republic.
    Petrič, Marko
    University of Ljubljana, Slovenia.
    Hydrophobicity and resistance against microorganisms of heat and chemically crosslinked poly(vinyl alcohol) nanofibrous membranes2019In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 360, p. 788-796Article in journal (Refereed)
    Abstract [en]

    Poly(vinyl alcohol) (PVA) is a water-soluble, semi-ionic and biocompatible polymer with excellent chemical and thermal stability. The chemical crosslinking of PVA membrane improve its stability towards humidity and water. In the present work, PVA nanofibrous membranes were fabricated using roller electrospinning techniques. The prepared membranes were crosslinked by heat treatment, glutaraldehyde dipping, and glutaraldehyde vapour. Furthermore, octadecyltrichlorosilane (OTS) treatment was used for hydrophobization of the crosslinked membranes. The prepared crosslinked membranes were analysed by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The hydrophobization of PVA nanofibrous membranes were analysed by employing optical goniometer and auto-dynamic vapour sorption (AVS) techniques. Further, the PVA membranes were tested against algae and mould growth at in-vitro laboratory conditions. The SEM and FTIR results revealed significant differences in the morphology of the PVA nanofibrous membranes and in chemical bond formation due to crosslinking treatments. Water contact angle and AVS data confirmed a hydrophobization of PVA membranes by the treatments.

  • 15.
    Kumar, Eva
    et al.
    Yonsei Univ, Dept Environm Engn, Wonju 220710, Gangwon Do, South Korea.
    Bhatnagar, Amit
    Yonsei Univ, Dept Environm Engn, Wonju 220710, Gangwon Do, South Korea.
    Choi, Jeong-A
    Kumar, Umesh
    Min, Booki
    Kim, Yongje
    Song, Hocheol
    Paeng, Ki Jung
    Jung, Yong Mee
    Abou-Shanab, R.A.I.
    Jeon, Byong-Hun
    Perchlorate removal from aqueous solutions by granular ferric hydroxide (GFH)2010In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 159, no 1-3, p. 84-90Article in journal (Refereed)
    Abstract [en]

    The present research evaluates the efficacy of granular ferric hydroxide (GFH) for perchlorate removal from aqueous solutions. Laboratory scale experiments were conducted to investigate the influence of various experimental parameters such as contact time, initial perchlorate concentration, temperature, pH and competing anions on perchlorate removal by GFH. Results demonstrated that perchlorate uptake rate was rapid and maximum adsorption was completed within first 30 min and equilibrium was achieved within 60 min. Pseudo-second-order model favorably explains the sorption mechanism of perchlorate on to GFH. The maximum sorption capacity of GFH for perchlorate was ca. 20.0 mg g(-1) at pH 6.0-6.5 at room temperature (25 degrees C). The optimum perchlorate removal was observed between pH range of 3-7. The Raman spectroscopy results revealed that perchlorate was adsorbed on GFH through electrostatic attraction between perchlorate and positively charged surface sites. Results from this study demonstrated potential utility of GFH that could be developed into a viable technology for perchlorate removal from water.

  • 16.
    Kumar, Eva
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Bhatnagar, Amit
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Hogland, William
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Marques, Marcia
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Department of Sanitary and Environmental Engineering, Rio de Janeiro State University, UERJ, Rio de Janeiro, Brazil.
    Sillanpää, Mika
    Laboratory of Green Chemistry, Faculty of Technology, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli, Finland.
    Interaction of anionic pollutants with Al-based adsorbents in aqueous media – A review2014In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 241, p. 443-456Article in journal (Refereed)
    Abstract [en]

    Many anionic pollutants (e.g., fluoride, nitrate and nitrite, bromate, phosphate, arsenate and arsenite, selenate and selenite, perchlorate) have been detected in surface and groundwater in different parts of the world and strict measures are being taken to minimize their concentrations and to control their mobility in aqueous media. Mineral surfaces, in general, have shown enhanced uptake of many anionic pollutants. Various phases of aluminum (Al) oxides, hydroxides and oxyhydroxide are increasingly being employed as adsorbents for the detoxification of water and wastewater contaminated with anionic pollutants. Understanding the structural properties and morphology of adsorbents is important in order to gain knowledge about the governing mechanism behind the adsorption of anions by these adsorbents. The adsorption ability of aluminum oxides, hydroxides and oxyhydroxide depends on several key factors including properties of the adsorbent (surface area, pore size, pHpzc, porosity) and that of the adsorbates. This paper provides an overview of the physical and chemical properties of various aluminum oxides, hydroxides and oxyhydroxides and their application in water and wastewater treatment with the focus on the removal of anionic pollutants. Furthermore, the performance of these minerals and that of the synthetically prepared hybrid adsorbents (containing Al-minerals) for the adsorption of various anions has been reviewed with an emphasis on the behavior of adsorbent-water interface in presence of the anionic pollutants.

  • 17. Repo, E.
    et al.
    Mäkinen, M.
    Rengaraj, S.
    Natarajan, G.
    Bhatnagar, Amit
    Univ Porto, Fac Engn, Dept Engn Quim, LSRE, P-4200465 Oporto, Portugal .
    Sillanpää, M.
    Lepidocrocite and its heat-treated forms as effective arsenic adsorbents in aqueous medium2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 180, p. 159-169Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the adsorption potential of heat treated lepidocrocites (gamma-FeOOH) towards As(III) and As(V) ions in aqueous solutions. Initially, mesoporous lepidocrocite was synthesized, treated at different temperatures, and characterized using various analytical techniques. During the heating, transformation of lepidocrocite into hematite was observed. The adsorption of As(III) and As(V) was studied by batch experiments and the effects of different operational parameters e.g., adsorbent dose, solution pH, contact time, and the initial concentration of As(III)/(V) (isotherms) were studied. Lepidocrocite treated at 250 degrees C exhibited >99% and 94% adsorption from 50 mg/L As(V) and As(III) solutions, respectively with an adsorbent dose of 2.5 g/L. The highest uptake capacity was obtained for As(III) (55 mg/g) on lepidocrocite without the heat treatment and for As(V) (38 mg/g) on lepidocrocite treated at 250 degrees C, which was assigned to be a mixture of maghemite and hematite. The adsorption kinetic data fitted well with the pseudo-second-order model and the BiLangmuir isotherm had the best applicability to describe the adsorption equilibrium.

  • 18. Santo, C.E.
    et al.
    Vilar, V.J.P.
    Botelho, C.M.S.
    Bhatnagar, Amit
    Univ Porto, Fac Engn, LSRE Lab Separat & React Engn Associate Lab LSRE, P-4200465 Oporto, Portugal .
    Kumar, E.
    Boaventura, R.A.R.
    Optimization of coagulation-flocculation and flotation parameters for the treatment of a petroleum refinery effluent from a Portuguese Plant2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 183, p. 117-123Article in journal (Refereed)
    Abstract [en]

    Petroleum refineries generate significant amounts of wastewater which have to be treated and processed before their discharge into water streams. The refinery wastewater treatment plants (WWTPPs) employ physico-chemical processes to achieve effluents of satisfactory oil content to be further treated by biological processes. In the present study, coagulation-flocculation and flotation processes are optimised to reduce the concentrations of organic matter, oil and grease and other contaminants in order to obtain an effluent with suitable characteristics ready to be treated by an aerobic biological process. PAX-18 (17% Al2O3), aluminium sulphate (Al-2(SO4)(3)) and ferric sulphate (Fe-2(SO4)(3)) are chosen for affecting coagulation-flocculation as a primary treatment. NALCO 71408 is employed as flocculant. Treatment efficiency is evaluated in terms of chemical oxygen demand (COD), total organic carbon (TOC) and turbidity measurements. The experiments are conducted both in discontinuous and continuous mode to assess the feasibility of the process. Flotation is investigated as a post-treatment process for the removal of emulsified hydrocarbons and satisfactory results are obtained.

  • 19.
    Song, Wei
    et al.
    Harbin Inst Technol Shenzhen, Peoples Republic of China.
    Li, Ji
    Harbin Inst Technol Shenzhen, Peoples Republic of China.
    Fu, Caixia
    Southern Univ Sci & Technol, Peoples Republic of China.
    Wang, Zhuoyue
    Harbin Inst Technol Shenzhen, Peoples Republic of China.
    Zhang, Xiaolei
    Harbin Inst Technol Shenzhen, Peoples Republic of China.
    Yang, Jingxin
    Guangzhou Univ, Peoples Republic of China.
    Hogland, William
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Gao, Ling
    Beihua Univ, Peoples Republic of China.
    Kinetics and pathway of atrazine degradation by a novel method: Persulfate coupled with dithionite2019In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 373, p. 803-813Article in journal (Refereed)
    Abstract [en]

    Efficient and environmentally friendly activation methods of persulfate (PS) have gained growing attention in the remediation of water or soil polluted by organic contaminants. Among all, the exploration of effective and applicable method for the PS activation becomes one of the hottest topics in the field of organic degradation. Dithionite (DTN) was employed in this study to activate PS and applied to degrade Atrazine (ATZ) without secondary pollution. ATZ could be completely degraded within 90 min by PS/DTN system. ATZ degradation by PS obeyed the pseudo-first-order kinetics and the rate constant values increased from (4.71-5.05) x10(-3) min(-1) to (4.59-5.09) x10(-2) min(-1) with the addition of DTN. Sulfate radicals were verified to be the dominant reactive species through the radical scavenging experiment. PS/DTN system can remain a strong oxidative ability in the range of pH below 9.0. The presence of Cl-, natural organic matter (NOM), and high concentration of HCO3- may inhibit the removal of ATZ while the low concentration of HCO3- can slightly promote the degradation. It was found that the degradation pathways of ATZ by PS/DTN involved de-chlorination and hydroxylation, de-alkylation, and de-amination by the reactive species. The study reveals that PS/DTN system has the broad application prospect in the treatment of refractory pollutants.

  • 20. Vilar, V.J.P.
    et al.
    Valle, J.A.B
    Bhatnagar, Amit
    LSRE – Laboratory of Separation and Reaction Engineering, Associate Laboratory LSRE/LCM, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
    Santos, J.C.
    De Souza, S.M.A.G.U.
    De Souza, A.A.U.
    Botelho, C.M.S.
    Boaventura, R.A.R.
    Insights into trivalent chromium biosorption onto protonated brownalgae Pelvetiacanaliculata: distribution of chromium ionic species on thebinding sites2012In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 200-202, p. 140-148Article in journal (Refereed)
    Abstract [en]

    In the present study, biosorption of trivalent chromium by protonated brown algae, Pelvetia canaliculata, was studied in batch system. FTIR analyses provided information about the possible binding groups present in the algae, as carboxylic, hydroxyl and sulfonate groups. Potentiometric acid–base titrations showed a heterogeneous distribution of two major binding groups, carboxyl and hydroxyl ones, following the Quasi-Gaussian affinity constant distribution suggested by Sips, which allowed to estimate the maximum amount of acidic functional groups (2.26 ± 0.02 mmol g−1) and proton binding parameters () for an ionic strength of 0.2 M. The trivalent chromium removal was found to increase with pH and the maximum chromium uptake was observed at pH 4.0 (∼0.6 mmol/g), corresponding to 1.34 meq/g, since at that pH, 25.8% of total chromium is in the Cr3+ form and 72.7% as CrOH2+. An equilibrium model incorporating the hydrolysis reactions that chromium undergoes in the aqueous phase was able to predict the chromium biosorption at different pH values and chromium concentrations, enabling the prediction of the distribution of chromium ionic species on the binding sites. A mass transfer model provided a good representation of the chromium biosorption kinetics, resulting in intraparticle homogeneous diffusion coefficients of 4.6 × 10−7 cm2/s for Cr3+ and 1.8 × 10−8 cm2/s for CrOH2+. The distribution of chromium ionic species in the solution and on the binding sites was also predicted by the kinetic model.

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