Similar to chitin, chitosan is not expected to absorb visible light, therefore, the presence of the chitosan layer on HL–chitosan particles effectively enhanced the scattering efficiency of the coating film [32]. The HL–chitosan simultaneous exhibits high opacity and good formaldehyde adsorption ability.These properties of HL–chitosan give it the potential for use as a special white pigment with the capacity to chemically adsorb the indoor air pollutant formaldehyde [14].