New Bioadsorbent Derived from Winemaking Waste Cluster Stalks: Application to the Removal of Toxic Cr(VI) from Liquid Effluents  
[PERSON]  
1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.); [EMAIL_ADDRESS] (F.A.L.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.A.)1 National Center for Metallurgical Research (CENIM), Spanish National Research Council (CSIC), Avda. [PERSON] 8, 28040 Madrid, Spain; alcaraz@cenim.  
Several techniques for chromium removal from wastewaters have been reported, including chemical precipitation [8], electrochemical precipitation [9], solvent extraction [10], ion exchange [11], and adsorption process [5; 12; 13]. Due to its simplicity, effectiveness, and low cost, the adsorption process has been extensively investigated for metal removal from aqueous solutions. However, the great inconvenience in the application of this process by industries is the cost of adsorbents. Generally, the cost of commercial adsorbent is very high, which is a barrier to using the adsorption process [6].  
Activated carbons are useful adsorbent materials for the removal of a large variety of pollutants. It has been reported that it is possible to obtain them from renewable sources, such as from agro-industrial wastes and by new synthesis processes [14]. Among the great variety of wastes, winemaking waste is an attractive option due to the number of grapes produced worldwide and the amount of waste generated for winemaking [15]. Thus, the use of winemaking waste to obtain activated carbon and its use for heavy metals adsorption is an important aim in the scientific community for both heavy metal removal from wastewater and the reuse and recycling of a generated waste.  
In this paper, an activated carbon (AC) derived from a waste generated in wine production, cluster stalks, is described. Cr(VI) removal by adsorption process was assessed. Different parameters that affect the adsorption process such as stirring speed, solution pH, temperature, ionic strength, and adsorbent dosage were evaluated. Adsorption isotherms and kinetic studies were also investigated. Finally, Cr(VI) recovery from Cr(VI)-loaded carbon was addressed in several experimental conditions.