This study investigated the effects of SMT on biochar colloid transport using column experiments with five biochars produced from contrasting feedstocks, combined with spectroscopic (2D-COS-FTIR) and statistical analyses (linear regression, principal component analysis and random forest analysis) to identify the dominant controlling mechanisms. The results showed SMT adsorption capacity varied widely among the five biochars (1.86~4.52mg/g), and showed strong linear relationships with their carbon and hydrogen contents (R² > 0.70), highlighting the importance of feedstock-dependent physicochemical properties. The presence of SMT consistently shifted the zeta (ζ) potential of biochar colloids toward more positive values and markedly reduced the electrostatic energy barrier (Φ_max) between biochar colloid and quartz sand. This change substantially decreased colloid mobility (M_eff), indicating enhanced retention within the porous medium. Linear regression analysis showed that M_eff was closely related to the ζ potential (R²=0.88). In contrast, both PCA and random forest model analyses confirmed ζ potential as the most critical factor affecting M_eff. Furthermore, the fitting results from the two-site kinetic model (R²>0.97) showed that both the reversible site adhesion coefficient (k_att) and maximum solid concentration (S_max) increased for all five biochar colloids in the presence of SMT. These findings demonstrate that biochar feedstock types and SMT adsorption jointly influence the mobility of biochar colloid.