Colloidal stability of nanosized activated carbon in aquatic systems: Effects of pH, electrolytes, and macromolecules

New Insights into Aggregation Behaviors of the UV-Irradiated Dissolved Biochars (DBioCs) in Aqueous Environments: Effects of Water Chemistries and Variation in the Hamaker Constant

“…Larger k fast and lower CCC appeared in the CaCl 2 solution (Figures S12i and Figure b), indicating that Ca 2+ had a stronger capacity to destabilize DBioCs. According to the Schulze-Hardy rule, CCC is proportional to z n (n = −6 to −2; z is ion valence). , Counterions with higher valence possess more efficient charge screening capability, which echoes the above discussion on zeta potentials. CCC Ca /CCC Na ratios were 2 –4.13 , 2 –3.92 , 2 –4.35 , 2 –4.51 , 2 –4.82 , 2 –5.17 , and 2 –5.38 for W0d, W6h, W12h, W1d, W3d, W5d, and W7d, respectively (Table S5), well obeying the Schulze-Hardy rule (TEXT S7).…”

“…Obviously, acidic conditions were more favorable for DBioCs aggregation, whereas the opposite was true for the alkaline counterpart. This phenomenon also appeared in particles reported elsewhere. , The reason may be manifold. For one thing, under acidic conditions, excess free H + served as a counterion compressing the electric double layer (EDL) and protonated the DBioCs surface groups (e.g., −OH and −COOH), which made the DBioCs surface less negatively charged (Figures a and S8).…”