Adsorption of Cr (VI) pollutants in water using natural and modified attapulgite clay

Attapulgite clay also known as palygorskite is a mineral clay which possess good adsorption properties based \non its adsorption capacity, porous structure and moderate cation exchange properties. The study investigated \nthe effectiveness of naturally occurring and hydrochloric acid modified attapulgite as adsorbents for Cr (VI) \nremediation in wastewater. The physical properties of the clay were characterized using a range of \ntechniques. X-ray diffraction confirmed the purity of the clay while BET analysis indicated an increase in \nsurface area from 131.4 to 183.2 m2/g after acid modification. The modified attapulgite was predicted to have \nan adsorption capacity of 75 mg/g compared to 2.1 mg/g for the naturally occurring attapulgite. The increase \nin adsorption capacity was attributed to a change in surface area as well as changes in the surface chemistry \nof the clay. The adsorption isotherms were best described by the Langmuir mono-layer adsorption model \nwhile the kinetics fit the Langren first order kinetics model.