The preparation of opal/TiO2, SiO2/TiO2 composites and application as papermaking filler

Titanium dioxide (TiO 2 ) is widely recognized as a high-performance papermaking filler, yet its extensive industrial application is constrained by its elevated cost. To address this challenge, we developed a sustainable and cost-effective carbonation method to prepare TiO 2 based composite fillers. Using opal as an inorganic support and exploiting the hydrolysis behavior of TiO 2 under CO 2 induction, opal/TiO 2 and SiO 2 /TiO 2 composite materials were successfully synthesized. This approach utilizes inexpensive and renewable carbon dioxide and naturally occurring siliceous minerals, significantly reducing production cost while enhancing the dispersibility and structural stability of TiO 2 . When applied as papermaking fillers, the composites effectively improve paper whiteness, hiding power, and mechanical properties, enabling reduced consumption of pure TiO 2 and promoting environmental and economic benefits. When applied as papermaking fillers, the silica derived from opal imparted a high paper whiteness of up to 94.3%. With increasing TiO 2 content, the opal/TiO 2 composites enhanced paper whiteness from 74.7% to 84.8%. Both composite fillers significantly improved the hiding power of paper, approaching that of pure TiO 2 at high filler loadings. In addition, enhanced filler retention (up to approximately 44.5%) and increased tearing strength (∼106 mN) were achieved, indicating favorable fiber–filler interactions and effective mechanical reinforcement. Beyond practical industrial relevance, this work establishes a novel strategy for fabricating composite materials and elucidates the underlying formation mechanism, offering valuable insights for the development of functional composite fillers. The proposed method demonstrates strong potential for large-scale industrial implementation and contributes to green manufacturing and carbon-utilization technologies.