Yong-Seon Zhang, Jae-E Yang, Gye-Jun Lee, and Seon-Woong Hwang. National Institute of Highland Agriculture, RDA, Hoeng-gye, Doam, Pyeongchang 232-955, Gangweon, South Korea
The natural zeolite, produced in the Young-il Bay area of the Kyungpook province in Korea, contains more than two by-products in the mineralogical compositions. These characteristics have devaluated the practical use of the natural zeolite in many fields. Also lots of powdery zeolite of low quality have been produced as wastes while processing the natural zeolite into the products having a particular particle size. Objective of this research was to develop the heavy metal adsorbent, ZeoAds, with granulation of the powdery zeolite by mixing with Portland cement and treating at high temperature. The most effective conditions for the granular ZeoAds formulations were to mix the powdery zeolite (75%) with Portland cement (25%) as a cementing agent, to granulate using the extruder, to harden for 30 days at 25°C and to treat the granules at 400 °C for 3 hours. Amorphous oxide mineral was formed while formulating the ZeoAds, as proved in the wide spectra of the X-ray diffractogram. The alkali- or thermal-treated natural zeolite showed the pH-dependent charge characteristics. Capacity of the ZeoAds for heavy metal adsorption was increased with deceasing the particle size of the ZeoAds up to 2 mm. Below 2 mm in diameter, adsorption capacity of the ZeoAds was independent of the particle size. The selectivity of the ZeoAds for divalent cations were in the order of Pb > Cu > Zn > Cd. In this experiment, the ZeoAds as a heavy metal adsorbent was developed by employing a simple, easy and cost effective granulation process using the low quality powdery natural zeolite. Adsorption isotherm of ZeoAds for heavy metals followed the Langmuir type. The maximum adsorption capacity of ZeoAds was greater than that of the commercial activated carbon. The ZeoAds was more efficient than the commercial activated carbon in treatment of the heavy metals in the industrial waste water, as proved by breakthrough curve of the column leaching experiments.
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