A comparative study of arsenic(V), tetracycline and nitrate ions adsorption onto magnetic biochars and activated carbon

[Display omitted] •Magnetic biochars and magnetic activated carbon were successfully synthesized.•One-step magnetic biochar showed the highest sorption capacity for As(V) and NO3−.•Magnetization reduced the sorption capacity of tetracycline onto activated carbon.•Magnetic sorbents are promising materials to be applied in co-contaminated environment. The removal of contaminants in co-solute systems is a pressing issue. Herein, the adsorption capacities of magnetic biochars and activated carbon were investigated and compared for various aqueous anions, including As(V), tetracycline (TC) and NO3−, existed alone or as a mixture. One-step (pre-treating biomass with FeCl3 before pyrolysis (FB)) and two-step (pyrolysing biomass before modification with FeCl3 (BF)) magnetization methods were applied to synthesize magnetic biochars. Magnetic activated carbon (AF) was also prepared with the two-step magnetization method. FB presented the highest adsorption capacities for As(V) and NO3− respectively at 6.77 and 6.31mgg−1. AC (612.38mgg−1) showed the highest adsorption capacity for TC, which decreased by 189.76% after magnetization. Magnetization was proved to be a promising method to improve the adsorption of both As(V) and NO3− on adsorbents through enhanced electrostatic attraction, while the adsorption of TC depended mainly on high specific surface area of the adsorbent. Results from competitive adsorption in the co-solute systems suggested that FB had a great potential for application in the co-contaminated environment (heavy metal and inorganic anions), and AF could be a promising adsorbent to remediate multiple-contaminated environment (i.e. organic pollution and heavy metal/inorganic anions).