Comparative study of adsorption capacity of mesoporous silica materials for molsidomine: Effects of functionalizing and solution pH

• Molsidomine adsorption onto all silica adsorbents decreases with increasing pH.
• Phenyl modified silica materials (PhMS) adsorb the highest molsidomine amount.
• Hydrogen bonding is responsible for the drug adsorption on UMS and MMS.
• Molsidomine adsorption on PhMS occurs due to π–π interaction and hydrogen bonding.
• Molsidomine adsorption on AMS is the lowest and fixed only at pH 7.4.

Adsorption capacities of mesoporous silica materials having various surface functional groups (hydroxyl, phenyl, mercaptopropyl, aminopropyl) at pH values of 4.8, 7.4, and 8.0 were studied. It was found that the maximum amount of adsorbed molsidomine is affected by method of preparation of the silica materials, chemistry of their surfaces and solution pH from where adsorption is carried out. The effects were explained by different states of the adsorbents and molsidomine in solution at the studied pH. The most efficient adsorption of molsidomine is observed onto phenyl modified silica prepared by grafting at pH 4.8. Aminopropyl modified silica adsorbs the lowest amount of molsidomine and the adsorption was observed only at pH 7.4. Interactions responsible for the adsorption were elucidated by spectroscopic studies.