Journal of Colloid and Interface Science 217, 137–141 (1999)

Adsorption by activated red mud (ARM) is investigated as a possible alternative to the conventional methods of Cr(VI) removal from aqueous synthetic solutions and industrial effluents. Adsorption characteristics suggest the heterogenous nature of the adsorbent surface sites with respect to the energy of adsorption. Various factors such as pH, contact time, Cr(VI) concentration, amount of adsorbent, and temperature are taken into account, and promising results are obtained.
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Journal of Colloid and Interface Science 217, 137–141 (1999) Journal of Colloid and Interface Science 217, 137–141 (1999)Article ID jcis.1999.6288, available online at http://www.idealibrary.com on Adsorption of Hexavalent Chromium from Aqueous Solution by Using Activated Red Mud Jyotsnamayee Pradhan, Surendra Nath Das, and Ravindra Singh Thakur 1 Regional Research Laboratory (CSIR), Bhubaneswar 751013, India Received January 7, 1999; accepted April 14, 1999 ing its adsorption on activated carbon (2), starch xanthate (3), Adsorption by activated red mud (ARM) is investigated as a alumina (4), low-grade manganese ore (5), crushed coconutpossible alternative to the conventional methods of Cr(VI) re- shell (6), fly ash (7), sawdust (8, 9), rice husk carbon (10),moval from aqueous synthetic solutions and industrial effluents. wood charcoal (11), bituminous coal (12), and lignite (13).Adsorption characteristics suggest the heterogenous nature of the Removal of chromium by different physical and chemicaladsorbent surface sites with respect to the energy of adsorption. methods has been reviewed (14). In the present study theVarious factors such as pH, contact time, Cr(VI) concentration, material used is an industrial waste/byproduct of the aluminumamount of adsorbent, and temperature are taken into account, and industry. Here, an attempt is made to prepare activated red mudpromising results are obtained. The applicability of the Langmuir and to study its feasibility as an adsorbent for removal ofas well as Freundlich adsorption isotherms for the present system hexavalent chromium from aqueous solution/industrial efflu-is tested. The loading factor (i.e., milligrams of Cr(VI) adsorbedper gram of ARM) increased with initial Cr(VI) concentration, ents. The process is investigated as a function of pH, time,whereas a negative trend was observed with increasing tempera- concentration of adsorbate, amount of adsorbent, and temper-ture. The influence of the addition of anions on the adsorption of ature. The effects of other extraneous anions on the adsorptionCr(VI) depends on the relative affinity of the anions for the surface of Cr(VI) is also investigated.and the relative concentrations of the anions. © 1999 Academic Press Key Words: activated red mud; adsorption; hexavalent chro- EXPERIMENTALmium removal. Activated red mud is prepared (15) by simple acid dissolu- tion followed by ammonia precipitation and drying at 110°C. INTRODUCTION Procedural details are given in our earlier paper (16). Analyt- ical grade reagents are used to prepare KCl solution and buffer Rapid industrialization and usage of heavy metals in indus- solution to maintain the ionic strength and pH of the medium.trial processes have resulted in an unprecedented increase in The solutions of Cr(VI) are prepared from AR qualitythe heavy metal flux into groundwater and industrial effluents. K 2Cr 2O 7.Like many heavy metals, chromium in traces is necessary for Adsorption experiments for Cr(VI) were carried out inlife processes. However, with higher concentration of this 100-ml stoppered conical flasks by taking appropriate amountselement in environment and the consequent increase in human ...