ORIGINAL RESEARCH
Chromium (VI) Adsorption Characteristics of Bentonite Under Different Modification Patterns
Wenbin Li1, Zhaofu Meng1,2, Ze Liu1, Huayun Chen3, Qiong Wu1, Shaoe Xu4
 
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1Department of Natural Resource and Environment, Northwest A&F University, Yangling,
Shaanxi, 712100, China
2Key Laboratory of Plant Nutrition and Agri-Environment in Northwest China, Ministry of Agriculture,
Yangling 712100, China
3Department of Agricultural, Northwest A&F University, Yangling, Shaanxi, 712100, China
4Department of Biological and Agriculture Engineering, University of Arkansas,
Fayetteville 72707, USA
Publish date: 2016-05-25
Submission date: 2015-11-23
Final revision date: 2016-01-27
Acceptance date: 2016-01-30
 
Pol. J. Environ. Stud. 2016;25(3):1075–1083
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ABSTRACT
We investigated the Cr(VI) adsorption characteristics of bentonite under different modification patterns by using a mixture of BS-12 (dodecyl dimethyl betaine) and DTAB (dodecyl trimethyl ammonium bromide). DTAB was used to compositely modify 25%, 50%, and 100% BS-12-modifi ed bentonite (three modifi ed modes of bentonite with BS-12). In addition to these modification modes, variations as functions of pH value, temperature, and ionic strength were compared. Results showed:
  1. Cr(VI) adsorption capacity of bentonite compositely modifi ed with BS (short for BS-12) + DT (short for DTAB) rapidly increased compared with that of BS-modifi ed bentonite, and the adsorption capacity of 100%BS+100%DT-modified bentonite was the highest among the samples surveyed and 23-fold higher than that of CK (raw bentonite).
  2. Cr(VI) adsorption on bentonite exhibited saturated adsorption in ion exchange (IE) mode, distributive adsorption in ion exchange and hydrophobic bond coexisting (IE+HB) pattern, and synergistic adsorption in the hydrophobic bond (HB) pattern.
  3. Effects of rising temperature on Cr(VI) adsorption appeared in the IE mode, while negative temperature effect was observed in the HB mode. Higher pH value and ionic strength were unfavorable for Cr(VI) adsorption. 100%BS+100%DT compositely modified bentonite exhibited the optimal adsorption of Cr(VI) at 10ºC, pH = 4, and ionic strength of 0.01 mol L−1.
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