Removal of nitrite from aqueous solution by Bacillus amyloliquefaciens biofilm adsorption

A newly verified adsorbent biofilm produced by Bacillus amyloliquefaciens DT was investigated for nitrite removal from aqueous solutions. The biofilm’s characteristics and adsorption mechanism were determined, with results indicating that nitrite ions were adsorbed onto the protonated amine sites of biofilm under acidic conditions. Analysis of various factors showed that higher nitrite adsorption capacities occurred at pH < 3.0 and higher temperatures as well as higher initial nitrite concentrations, with a maximum nitrite removal capacity of 116.84   mg/g. Furthermore, nitrite adsorption was well fitted to the pseudo second-order and Weber–Morris kinetic models, and the Freundlich and Sips isotherm models. Simultaneously, thermodynamic analysis demonstrated that nitrite adsorption is a spontaneous endothermic process. In summary, the adsorption of nitrite was complex, and mainly resulted from electrostatic attraction and intraparticle diffusion. Consequently, the B. amyloliquefaciens biofilm can be considered as a promising adsorbent for nitrite removal from wastewater.