In　a　previous　study,　we　used　a　sol-hydrothermal　method　with　a　one-stage　calcination　in　an　air　atmosphere　at　400　degrees　C　to　prepare　composites　of　Bi2O3-TiO2　supported　on　powdered　activated　carbon　(Bi-Ti/PAC-1).　However,　the　photocatalytic　efficiency　of　those　composites　was　relatively　low　due　to　their　high　band　gap　and　the　single　crystal　phase　of　their　TiO2.　To　improve　the　photocatalytic　efficiency,　we　developed　a　two-stage　calcination　method　with　a　first　calcination　in　air　at　300　degrees　C　followed　by　a　second　calcination　in　a　N-2　atmosphere　(at　500,　600,　or　700　degrees　C)　to　form　the　Bi2O3-TiO2　composites　(Bi-Ti/PAC-2).　Compared　with　Bi-Ti/PAC-1,　the　photocatalytic　degradation　efficiency　of　sulfamethazine　(SMT)　by　Bi-Ti/PAC-2-700　increased　by　32　%　under　solar　light　irradiation.　Bi-Ti/　PAC-2-700　contained　two　TiO2　crystal　phases,　ruffle　and　anatase,　and　its　band　gap　was　2.58　eV,　far　less　than　that　of　Bi-Ti/PAC-1.　Electron　paramagnetic　resonance　measurements　and　trapping　experiments　showed　that　the　superoxide　radical,　hole,　and　hydroxyl　radical　each　played　an　important　role　in　the　degradation　of　SMT,　among　which　the　superoxide　radical　predominated.　The　degradation　pathway　of　SMT　included　four　processes:　oxidation　of　hydroxyl　radical,　SO2　extrusion,　N-C　and　S-N　bond　cleavage.　We　also　determined　that　solution　pH,　humic　acid,　and　inorganic　ions　had　varying　effects　on　the　photocatalytic　degradation　capability　of　Bi-Ti/PAC-2-700.　We　measured　the　efficiency　of　Bi-Ti/PAC-2-700　for　SMT　degradation　in　natural　river　and　lake　water　and　found　it　to　be　＞　85　%,　sufficient　for　practical　applications.　This　study　provides　a　green　and　efficient　photocatalyst　that　can　be　applied　to　water　treatment　processes.