In this work, the commercial Hombikat UV-100 anatase (A) was calcined at 1000 °C for 4 h to obtain a rutile phase grown on anatase (A), proven by X-ray diffraction pattern. The dry powder of A and A were physically mixed to form A + A samples in different ratios. Although the characterization of A revealed that it had microstructure bigger than A, lower surface area, lower water-molecule absorption, higher surface states and lower charge separation, all mixed A + A samples, which had physically-induced tuning in phase heterojunction, outperformed the commercial TiO P25 in acetaminophen (ATM) photodegradation efficiency. This could be due to effective charge separation and more active sites involved in A + A samples as seen in the depicted Z-scheme mechanism based on their band-edge positions obtained from Mott-Schottky analysis, scavenger tests and ATM photodegradation efficiency. In addition, this work also showed that band-edge positions, band-gap energy and heterojunction were correlated in determining the ATM photodegradation efficiency.