水质条件对膜-羧基官能团之间微观作用力的影响特征

为了探讨pH值、离子强度及膜材料对膜-污染物间相互作用力的影响特征,利用自制的典型膜污染物羧基官能团胶体探针,结合原子力显微镜定量考察了羧基官能团与PVDF及EVOH超滤膜间的相互作用力随pH值及离子强度的变化特征.结果表明:带有羧基基体的污染物与PVDF及EVOH超滤膜之间的相互作用力皆随着pH值的增大而减小;但是上述作用力随着离子强度的增加呈现特殊的变化趋势:在离子强度为0~10mmol/L时,膜-带有羧基基体的污染物之间相互作用力随着离子强度的增加而增大;在离子强度为10~500mmol/L时,膜-羧基之间相互作用力随着离子强度的增大而减小.在特定的水质条件下,EVOH-羧基间的作用力远小于PVDF-羧基之间的作用力.

Influence of solution chemistry on the interaction forces between membranes and carboxyl groups

To further clarify the effects of pH and ionic strength on the interaction forces between typical membrane materials and the carboxyl group, which is a typical functional group of membrane foulants, the interaction forces between the PVDF or EVOH membrane and carboxyl group were measured by atomic force microscopy in conjunction with a self-made carboxyl colloidal probe. Results show that the PVDF-carboxyl and EVOH-carboxyl adhesion forces weakened with increasing pH, whereas they firstly increased and then decreased with an increase in ionic strength. The interaction forces between membranes and carboxyl groups increased with an increase at low ionic strength (0~10mmol/L). However, the forces decreased with an increase at high ionic strength (10~500mmol/L). Moreover, the PVDF-carboxyl adhesion force was much stronger than the EVOH-carboxyl interaction force for given solution conditions.