Abstract
Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually disposed of in landfills directly, and recycling has rarely been reported. In this study, the spent MTP catalyst was moderately dealuminized with organic acids and etched with alkali solvent to increase its specific surface area, further silanized by octyl triethoxy silane (OTS). A novel superhydrophobic adsorbent covered with –Si(CH2)7CH3 groups was obtained. The characterization of XRD, SEM, FTIR and XPS shows that the adsorbent maintains a typical ZSM-5 zeolite structure, and the –Si(CH2)7CH3 group is successfully grafted into the sample, not only on the surface but also in some pore space. Taking high chemical oxygen demand (COD) wastewater as the object, the influence of contract time, pH and temperature on COD removal was investigated. The removal process could be better depicted by the Langmuir isotherm model and the pseudo second-order dynamic model. Furthermore, the results of the thermodynamic study (∆G is − 79.35 kJ/mol, ∆S is 423.68 J/mol K, and ∆H is 46.91 kJ/mol) show that the adsorption was a spontaneous and endothermic process. These findings indicate that the modified spent MTP catalyst has potential application for the removal of COD from wastewater.
Highlights
Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually disposed of in landfills directly, and recycling has rarely been reported
After treatment with acid and alkali, the spent MTP catalyst was modified using octyltriethoxysilane (OTS), and the –Si(CH2)7CH3 group was successfully grafted onto the surface of the adsorbent
The characterization of BET and XPS indicated that the silane group has been grafted on the surface and pore channel of the ZSM-5 zeolite and occupied the internal space of the pore channel
Summary
Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually disposed of in landfills directly, and recycling has rarely been reported. The spent MTP catalyst has a large specific surface area, high porosity, and good adsorption performance.
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