This study aimed to prepare zeolite from rice hull, characterize the prepared zeolite and apply it in the removal of nitrate in water. It specifically aimed to prepare zeolite from the pretreated rice hulls prior to ashing, determine the alumina and silica ratio content of the produced zeolite samples and its extra mineral contents by energy dispersive X-ray spectroscopy (EDX), characterize the different zeolite samples by X-ray diffraction (XRD) method and scanning electron microscopy (SEM), and test the ability of the rice hull-derived zeolites in cleaning water which contains nitrates. Distilled water and 1M HCl were used in the pretreatment of rice hull before ashing. Purity of the rice hull ashes obtained in the process was verified by determining their percent carbon content. Using EDX, the alumina and silica ratios were calculated from the data gathered. SEM was used to determine the shape and pore size and XRD method to know the possible crystal lattice of the prepared zeolites. The rice hull washed with water (RHA-W) has 21:16 (Si:Al) framework ratio while that acid-washed (RHA-A) 23:17 (Si:Al) which could mean that the Si-Al framework ratio of the samples are 1.3:1 and 1.4:1, respectively. SEM scans at 7500x magnification revealed that zeolites derived from RHA-W has bigger pore sizes (2 µm) compared to those derived from RHA-A with approximately 1µm diameter. Using XRD spectroscopy, the rice hull-derived zeolites possible lattice was determined and both were not simple cubic crystals. Zeolites are framework aluminum silicates, composed of tetrahedral atomic groups of SiO45- and AlO45-, linked to form complex, three-dimensional networks. The trapping and exchanging capacity of the prepared zeolites were determined by treating a water sample with 69.0 ppm of NO3- and loading it with 0.2 g zeolite per liter of solution. Results show that the zeolite derived from RHA-W was able to decrease the concentration of nitrate in water by 99.11% while that derived from RHA-A by 99.26%. Both prepared zeolites removed higher concentrations of NO3- compared to the commercial zeolite which gave only 98.77% nitrate removal.
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