Study On Adsorption Of Copper Ions?Chromium Ions By Organic Modified Bentonite

Bentonite minerals is abundant in China,it is widely used in various industries because of its special crystal structure with many excellent characteristics,such as dispersive suspension,thixotropism,absorbability and cation exchange,etc.In recent years,treating the heavy metal ions in waste water by using bentonite has been widely applied at home and abroad.In this experiment,Na₂CO₃ was used as sodium agent,cetyltrimethyl ammonium bromide and octadecyl trimethyl ammonium chlorid was used as organic modifiers to Ca-bentonit by Na-modification and organic modification was used to treate the waste water containing copper ion and chromium ion,the effects of pH value,adsorbent dosage,adsorption time on the adsorption effect were investigated;the isothermal adsorption model and kinetics equation of two kinds of organic bentonite for waste water adsorption containing copper ion and chromium ion were studied,the experiment results showed that:The bentonite samples are-200 mesh,Na₂CO₃ is used as sodium agent,the effect of Na-modification is the best when the sodium time is 30 minutes and the dosage of sodium agent is 6%?Na₂CO₃:bentonite?;Na-bentonite was organic modified by using cetyltrimethyl ammonium bromide and octadecyl trimethyl ammonium chlorid,the dosage of two organic modifiers were calculated through the cation exchange capacity of bentonite,the organic modified bentonites are prepared under the conditions of stirring time is two hours and temperature is 60?.The optimum adsorption conditions of various bentonites were determined through the study of adsorption of waste water adsorption containing copper ion and chromium ion by Ca-bentonite,CTAB organic bentonite and STAB organic bentonite.The adsorption rate of Ca-bentonite on copper ion reached 95.74%under the conditions of pH values is about 4.00,adsorbent dosage is 2.5g/L and adsorbing time is 30min;the adsorption rate of CTAB organic bentonite and STAB organic bentonite on copper ion reached 97.6%and 98.4%separately under the conditions of pH values is about 4.00,adsorbent dosage is 3.0g/L and adsorbing time is 30min;the adsorption rate of CTAB organic bentonite and STAB organic bentonite on chromium ion reached 83.8%and 87.1%separately under the conditions of pH values is about4.45,adsorbent dosage is 3.0g/L and adsorbing time is 30 min.Isothermal adsorption was studied by Freundlich isotherm model and Langmuir isotherm model.The results show that the adsorption of CTAB organic bentonite and STAB organic bentonite to copper ion and chromium ion is more in line with Freundlich isothermal model.It shows that the adsorption of organic modified bentonites to copper ion and chromium ion is between single-layer and multi-layer adsorption,and the adsorption surface of organic modified bentonites are not equal.The kinetics equation of adsorption of copper ion and chromium ion on CTAB organic bentonite and STAB organic bentonite showed that the organic bentonite had good adsorption performance for copper ion and chromium ion,and met the pseudo-second-order kinetic,the adsorption rate constant k₂ shows that the adsorption rates of two kinds of organic bentonite on copper ion and chromium ion are fast.The above results show that the organic modified bentonite can effectively remove copper ion and chromium ion in the waste water.