Dear Abdus, please be aware that biochars usually contain ash, which biases analyses of surface funtionality (e.g. by Böhm tittration) and CEC (Fidel et a., 2013, doi: 10.2134/jeq2013.07.0285; Singh et al, 2010, doi: 10.1071/SR10058). Thus, please check biochar for ash content and remove slightly (...to prevent chemical impact on surface functional groups; Leon y Leon et al. 1992, doi: 10.1016/0008-6223(92)90164-r) prior analysing CEC and surface functionals groups. BR Nils