Perhydropolysilazane (PHPS) was chemical modified with alcohol derivative (ROH, R = CH 3 , i-C 3 H 7 , n-C 5 H 11 , n-C 10 H 21 ) at the silicon (Si) of PHPS/ROH molar ratio of 4/1. The alkoxy group-functionalized PHPS was converted into amorphous silica powders by curing at 270°C to promote oxidative crosslinking, followed by pyrolysis at 600°C in air to complete the polymer/amorphous silica conversion. Thermogravimetric analysis in air of the 270°C-crosslinked PHPS showed an approximately 18% weight gain at 200 to 500°C. This weight gain was suppressed consistently with the number of carbon atoms of the alkoxy groups introduced to PHPS. Upon heating to 600°C, the PHPS modified with n-C 5 H 11 OH showed a total weight loss of 12%, and further weight loss of 31% was observed for the PHPS modified with n-C 10 H 21 OH. The nitrogen sorption analysis revealed that micropore volume of the polymer-derived amorphous silica increased consistently with the weight loss during the pyrolysis up to 600°C, and the amorphous silica derived from the PHPS modified with n-C 10 H 21 OH exhibited the highest micropore volume. Further increase in the micropore volume was achieved by increasing the Si/n-C 10 H 21 OH molar ratio from 4/1 to 2/1. The micropore volume and specific surface area of the resulting amorphous silica powders were 0.193 cm 3 /g and 370 m 2 /g, respectively.

Natural zeolite is widely used in removing ammonia via adsorption process because of its superior ion-exchange properties. Ceramic particle size affects the adsorptivity of particles toward ammonia. In this study, hollow fiber ceramic membrane (HFCM) was fabricated from natural zeolite via phase inversion. The effect of natural zeolite particle size toward the properties and performance of HFCM was evaluated. The results show that the HFCM with smaller particle sizes exhibited a more compact morphological structure with better mechanical strength. The adsorption performance of HFCM was significantly improved with smaller particle sizes because of longer residence time, as proven by the lower water permeability. A high adsorption performance of 96.67% was achieved for HFCM with the smallest particle size (36 μm). These findings provide a new perspective on the promising properties of the natural zeolite-derived HFCM for ammonia removal.

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