Preparation of a Mesoporous Ceramic Adsorbent Based on Iranian Domestic Kaolin to Utilize as Slow-Release Urea Fertilizer Medium

Overusing nitrogen fertilizer causes some serious problems for water resources, soil, and agriculture products. Researchers have been trying to develop effective means which may use less amount of fertilizers containing nitrogen. In this work, cost-effective ceramic granule adsorbent was prepared to be used as a fertilizer carrier of controlled release behavior. A mixture of ۷۰ wt.% domestic kaolin and ۳۰ wt.% gibbsite was used to produce the granules. By utilizing thermal analysis of raw granule, the calcination temperatures were obtained and the effect of various calcination temperatures of ۵۰۰, ۶۰۰, and ۷۰۰˚C on the water adsorption was studied. The characteristics of granules were investigated by XRD, BET, FTIR, and SEM analyses. The results showed that by increasing the calcination temperature, the crystal structure of the granules was transformed into a dehydrated form and by calcination at ۶۰۰°C the specific surface area of granules increased from ۷.۵۰ to ۵۳.۴۵m۲/g. The granules were soaked in a ۵۰۰g/lit solution of urea, where they adsorbed about ۱۰wt.% urea. The dried urea-loaded granules were placed in water where the release of urea was measured by UV-vis spectrophotometry. Finally, different portions of urea-loaded granules were evaluated as fertilizer in the growing bed of corn plant where the height and the stem diameter of samples were compared with a control sample as well as a sample fertilized by urea directly. The results showed that by using the loaded granules, the urea consumption can be reduced by ۵۰%.

Keywords:

ceramic adsorbent , clay , gibbsite , nitrogen fertilizer , calcination , slow-release fertilizer