Magnetically modified biochar for organic xenobiotics removal Ivo Šafar ̌ ík, Zdenka Made ̌ rová, Kristýna Pospíšková, Hans-Peter Schmidt, Eva Baldíková, Jan Filip, Michal Kr ̌ ížek, Ondr ̌ ej Malina and Mirka Šafar ̌ íková ABSTRACT Large amounts of biochar are produced worldwide for potential agricultural applications. However, this material can also be used as an efficient biosorbent for xenobiotics removal. In this work, biochar was magnetically modified using microwave-synthesized magnetic iron oxide particles. This new type of a magnetically responsive biocomposite material can be easily separated by means of strong permanent magnets. Magnetic biochar has been used as an inexpensive magnetic adsorbent for the removal of water-soluble dyes. Five dyes (malachite green, methyl green, Bismarck brown Y, acridine orange and Nile blue A) were used to study the adsorption process. The dyes adsorption could be usually described with the Langmuir isotherm. The maximum adsorption capacities reached the value 137 mg of dye per g of dried magnetically modified biochar for Bismarck brown Y. The adsorption processes followed the pseudo-second-order kinetic model and the thermodynamic studies indicated spontaneous and endothermic adsorption. Extremely simple magnetic modification of biochar resulted in the formation of a new, promising adsorbent suggested for selected xenobiotics removal. Ivo Šafař ík (corresponding author) Mirka Šafař íková Department of Nanobiotechnology, Biology Centre, ISB, ASCR, Na Sádkách 7, C ̌ eské Budě jovice 370 05, Czech Republic E-mail: ivosaf@yahoo.com Ivo Šafař ík Kristýna Pospíšková Jan Filip Michal Kř ížek Ondř ej Malina Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, Olomouc 783 71, Czech Republic Ivo Šafař ík Zdenka Madě rová Eva Baldíková Mirka Šafař íková Global Change Research Institute, ASCR, Na Sádkách 7, C ̌ eské Budě jovice 370 05, Czech Republic Hans-Peter Schmidt Ithaka Institute for Carbon Strategies, Ancienne Eglise 9, Arbaz CH-1974, Switzerland Key words | adsorption, biochar, magnetic iron oxide particles, magnetic modification, organic dyes ABBREVIATIONS ADP advanced data processing b constant related to the affinity of the binding sites (L/mg) B Cþ positive coercivity B C– negative coercivity BET(3) Brunauer Emmet Teller (model) BJH Barrett Joyner Halenda (model) C 0 total (initial) concentration of dye used in the experiment (μg/mL) C eq equilibrium liquid-phase concentration of the unadsorbed (free) dye in the supernatant (μg/ mL; mg/L) C t concentration of dye in solution (mg/L) in time t (min) DFT density functional theory EDS energy dispersive X-ray spectrometry FC field-cooled magnetization curve ΔG o Gibbs free energy change (J/mol) ΔH o standard enthalpy change (J/mol) HK Horvath and Kawazoe (model) k 1 the first-order rate constant (1/min) k 2 the second-order rate constant (g/mg min) K d thermodynamic equilibrium constant M maxþ (5 T) maximum magnetization at 5 T M max– (– 5 T) maximum magnetization at –5T M Rþ positive remanent magnetization M R– negative remanent magnetization MD molecular dynamics 1706 © IWA Publishing 2016 Water Science & Technology | 74.7 | 2016 doi: 10.2166/wst.2016.335 Downloaded from https://iwaponline.com/wst/article-pdf/74/7/1706/458749/wst074071706.pdf by guest on 26 May 2020