Preparation of a spherical biochar colloidal probe and its application in deciphering the mechanism of biochar mitigating membrane fouling

•Biochar microspheres and spherical biochar colloidal probes were prepared.•Spherical biochar had superior properties to irregular biochar.•Dosing biochar can efficiently mitigate protein (BSA) fouling.•Biochar’s influence on membrane fouling was predicted using force measurements.