The Effect Of Modified Natural Clinoptilolite On Its Adsorption Properties To K~+ In Seawater

Because China is a predominately agricultural country,potassium as an indispensable nutrient element for crop growth,has a very important special status in the agricultural production at our country.As a non-renewable resources,potassium reserves in China accounts for only a small portion of the world and it’s difficult to be mined.There is a large amount of potassium in seawater and China is rich in seawater resources,so the development of extracting potassium from seawater to solve the acute shortage of potassium resources is a potential technology in china from a long-term and sustainable development.Due to its characteristics of the well selective adsorption performance for K~+ and non-pollution for marine environment,natural clinoptilolite is considered to be more promising adsorbent in extracting potassium from seawater.But the natural clinoptilolite have a high silica alumina ratio and a lower adsorption capacity of K~+ in seawater.Therefore,natural clinoptilolite need to be modified to improve its adsorption performance.Through desilication and realuminization modification and salt modified composite process,the adsorption capacity to K~+ in seawater of the natural clinoptilolite was improved.The optimal modified clinoptilolite to adsorp K~+ in simulated seawater was studied.The modified zeolite with high adsorption capacity was characterized by the thermal gravimetric analyzer,X-ray fluorescence analyser,X-ray powder diffractometer,the specific surface area and pore size analyzer,scanning electron microscope,and the adsorption principle of K~+ was explored.The modified zeolite was analysized and it is demonstrated that when the 40-80 mesh natural clinoptilolite was calcinated for 1.5h at 200 ℃ ultrasonic processed with 0.2mol/L NaOH for 2.0h,followed by ultrasonic processing by 0.5mol/L AlCl3 for 2.0h,and then boiled by 20%(co)NaCl for 30min.When the modified zeolite was adsorpted at 25 ℃ for 6.Oh,it reached equilibrium.The optimum equilibrium adsorption capability to K~+(25.64mg/g)was obtained which was 4.2 times of natural clinoptilolite.The the adsorption to K~+ in the seawater of the optimal modified clinoptilolite was studied.It is concluded that the adsorption dynamics process of the best modified zeolite adsorbent K~+ in seawater can be better fit by the pseudo-second-order model equation and the linear correlation coefficient was 0.99.The adsorption isothermal curve well conform to the Langmuir isothermal adsorption model and Freundlich isothermal adsorption model,and the adsorption process of the modified zeolite to K~+ is a chemical monolayer adsorption process.After the modified clinoptilolite and nature clinoptilolite was characterized,the results showed that the channel of the modified zeolite was clear,its pore become loose,its specific surface area was increased,the silica alumina ratio was reduced,the ion exchange ability was improved,and it did not affect on the skeleton structure of modified clinoptilolite.