Nickel Oxide Grafted Andic Soil for Efficient Cesium Removal from Aqueous Solution: Adsorption Behavior and Mechanisms

An andic soil, akadama clay, was modified with nickel oxide and tested for its potential application in the removal of cesium from aqueous solution. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and powder X-ray diffraction (XRD) results revealed the nickel oxide was successfully grafted into akadama clay. N2 adsorption–desorption isotherms indicated the surface area decreased remarkably after modification while the portion of mesopores increased greatly. Thermogravimetric-differential thermal analysis (TG-DTA) showed the modified akadama clay had better thermostability than the pristine akadama clay. Decreases in cation exchange capacity (CEC) and ζ-potential were also detected after the modification. Adsorption kinetic and isotherm studies indicated the adsorption of Cs+ on the modified akadama clay was a monolayer adsorption process. Adsorption capacity was greatly enhanced for the modified akadama clay probably due to the increase in negative surface charge caused by the modification. The adsorption of Cs+ on the modified akadama clay was dominated by an electrostatic adsorption process. Results of this work are of great significance for the application of akadama clay as a promising adsorbent material for cesium removal from aqueous solutions.