Control on shape, porosity and surface hydrophilicity of hematite particles by using polymers

The shape, porosity, and surface hydrophilicity of hematite particles formed from a forced hydrolysis reaction of acidic FeCl₃ solution were controlled by using a trace of polymers (0.001 and 0.003 wt%). The spherical particles were produced on the systems with polyvinyl alcohol (PVA) and polyaspartic acid (PAS). In the case of polyacryl amide (PAAm), slightly small spherical particles were precipitated at 0.003 wt%. However, polyacrylic acid (PAAc) and poly-γ-glutamic acid (PGA) gave ellipsoidal particles. This morphological change on hematite particles depended on the order of functional groups of polymers as -OH<-CONH₂<-COOH<-COOH and ⟩C=O, corresponding to the order in extent of polymer molecules for complexation to Fe³⁺ ions and adsorption onto particle surface. Accompanying this order, the hematite particles produced were changed from less porous to microporous. On the other hand, only the system with 0.003 wt% of PAAm produced mesoporous hematite particles. Choosing the kinds of polymers also controlled the ultramicroporosity and surface hydrophilicity of the particles.