title: Utilization of magnetically responsive cereal by-product for organic dye removal.
abstract: BACKGROUND
  Barley straw, an agricultural by-product, can also serve as a low-cost and relatively efficient adsorbent of various harmful compounds. In this case, adsorption of four water-soluble dyes belonging to different dye classes (specifically Bismarck brown Y, representing the azo group; methylene blue, quinone-imine group; safranin O, safranin group; and crystal violet, triphenylmethane group) on native and citric acid-NaOH-modified barley straw, both in magnetic and non-magnetic versions, was studied.
  
  
  RESULTS
  The adsorption was characterized using three adsorption models, namely Langmuir, Freundlich and Sips. To compare the maximum adsorption capacities (qmax), the Langmuir model was employed. The qmax values reached 86.5-124.3 mg of dye per g of native non-magnetic straw and 410.8-520.3 mg of dye per g of magnetic chemically modified straw. Performed characterization studies suggested that the substantial increase in qmax values after chemical modification could be caused by rougher surface of adsorbent (observed by scanning electron microscopy) and by the presence of higher amounts of carboxyl groups (detected by Fourier transform infrared spectroscopy). The adsorption processes followed the pseudo-second-order kinetic model and thermodynamic studies indicated spontaneous and endothermic adsorption.
  
  
  CONCLUSIONS
  The chemical modification of barley straw led to a significant increase in maximum adsorption capacities for all tested dyes, while magnetic modification substantially facilitated the manipulation with adsorbent.
authors.affiliation: Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, 370 05, Ceske Budejovice, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Baldikova
authors.affiliation: Laboratory of Simulation of Industrial Processes, Department of Industrial Management and Technology, University of Piraeus, 18534, Piraeus, Greece.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Politi
authors.affiliation: Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, 370 05, Ceske Budejovice, Czech Republic.
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Maderova
authors.affiliation: Regional Centre of Advanced Technologies and Materials, Palacky University, 783 71, Olomouc, Czech Republic.
authors.forename: Kristyna
authors.initials: K
authors.lastname: Pospiskova
authors.affiliation: Laboratory of Simulation of Industrial Processes, Department of Industrial Management and Technology, University of Piraeus, 18534, Piraeus, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Sidiras
authors.affiliation: Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, 370 05, Ceske Budejovice, Czech Republic.
authors.forename: Mirka
authors.initials: M
authors.lastname: Safarikova
authors.affiliation: Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, 370 05, Ceske Budejovice, Czech Republic.|Regional Centre of Advanced Technologies and Materials, Palacky University, 783 71, Olomouc, Czech Republic.
authors.forename: Ivo
authors.initials: I
authors.lastname: Safarik
mesh_terms: D000327:Adsorption; D018533:Biomass; D004396:Coloring Agents / Q000737:chemistry*; D001467:Hordeum / Q000737:chemistry*; D007220:Industrial Waste; D007700:Kinetics; D008280:Magnetics; D008855:Microscopy, Electron, Scanning; D018547:Plant Stems / Q000737:chemistry*; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D007220:Industrial Waste; D014874:Water Pollutants, Chemical
keywords: barley straw; magnetic adsorbent; magnetic modification; microwave-assisted synthesis; organic dyes