As an alternative solution to the limitations in adsorption properties of natural diatomite caused by its physicochemical structure defects and modification effects to diatomite using conventional physical/chemical methods, the diatomite was pillared using poly-hydroxy-aluminum to improve its adsorption properties. The change in physicochemical characteristics of the diatomite before and after pillaring were analyzed by Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD). The difference in surface properties of diatomite and its adsorption characteristics of Cu2+, Zn2+ before and after pillaring were analyzed at the same time. The obtained results showed that the optimal conditions for diatomite pillaring were 2.2 of the [OH-]/[Al3+] molar ratio, 1.8 mol·L-1 of potassium chloride, 10 mmol·g-1 of the Al/diatomite ratio, 60℃ of the pillaring temperature, 24 h of the pillaring time, 200℃ of the aging temperature, and 0.5 h of the aging time. After pillaring, the poly-hydroxy-aluminum was successfully exchanged into the diatom shell, forming available pillars, which increased channel spacing, expanded adsorption reaction interface, increased the number of microporous surface hydroxy groups and enhanced the microporous surface activity. The Cu2+, Zn2+ adsorption data obtained both before and after pillaring well fitted the Langmuir isotherm model and the pseudo-second-order kinetics model. After pillaring, the adsorption capacity of Cu2+, Zn2+ onto diatomite reached 7.491, 11.312 mg·g-1, with an increasing percentage of 32.9%, 33.3% respectively, the diatomite adsorption capacity got great improvement.
Keywords: Cu2+; Zn2+; adsorption; diatomite; pillaring; polyglycolic aluminum.