Highly efficient activation of sulfite by p-type S-doped g-C3N4 under visible light for emerging contaminants degradation

•The n-type g-C3N4 was converted to p-type by substituting the N2C positions by S.•SCNs showed enhanced photoelectric capability and increased VB potential.•The p-type SCN was for the first time applied in sulfite activation.•The 1:1SCN showed significant advantages in adapting to complex water qualities.•The h+ and SO5•− were identified as the dominant contributors to DCF degradation.