Efficient removal of formaldehyde by polyethyleneimine modified activated carbon in a fixed bed

Polyethyleneimine modified activated carbon (PEI-AC) was prepared through a treatment of immersion, and used for the adsorption of formaldehyde. The adsorption capacity of formaldehyde by unmodified AC is 190.1 mg g^-1, and the adsorption capacity of formaldehyde can reach to 317.6 mg g^-1 after 10 g L^-1 of PEI modified, being about 1.67 times than unmodified activated carbon (AC: 191.2 mg g^-1). And the 10 g L^-1 of PEI modified AC (PAC-30) has the highest adsorption capacity of formaldehyde, reached to 650 mg g^-1, with an increasing magnitude of 240% in comparison with that without modified AC. This is mainly due to changes in the pore structure and surface functional groups after modification. However, as the PEI concentration increases, the adsorption performance is inhibited. Through kinetic studies, it was found that all adsorption curves follow the second-order kinetics, and the breakthrough curves follow the Boltzmann model, and the adsorption process can also be described by the intraparticle diffusion model.