Performance and mechanism of U(vi) removal from solution by humic acid-coated Fe₃O₄ nanoparticle-modified biochar...

The adsorbent material humic acid-coated Fe₃O₄ nanoparticle-modified biochar from filamentous green algae was fabricated by introducing the composites of humic acid-coated Fe₃O₄ nanoparticles onto biochar from filamentous green algae using the co-precipitation method. Then, the removal of U(vi) from solution by humic acid-Fe₃O₄/BC was carried out through batch experiments. The results of the characterization showed that the reaction conditions had an important influence on U(vi) removal by humic acid-Fe₃O₄/BC. The pseudo-second-order kinetic model and Langmuir model better illustrate the adsorption process of U(vi) on the surface of humic acid-Fe₃O₄/BC. The adsorption processes were dominated by chemisorption and monolayer adsorption. The maximum adsorption capacity of U(vi) by humic acid-Fe₃O₄/BC could be calculated, and it could reach 555.56 mg g^-1. The probable mechanisms of U(vi) removal by humic acid-Fe₃O₄/BC were reduction reaction, inner-sphere surface complexation and electrostatic adsorption. The high stability and reusability of humic acid-Fe₃O₄/BC made it more promising in U(vi) removal applications.