Adsorption studies of As(III) from wastewater with a novel adsorbent in a three-phase fluidized bed by using response surface method

Abstract

Existing overviews of arsenic removal include technologies that have traditionally been used (oxidation, precipitation/coagulation/membrane separation/adsorption) in static bed, with far less attention paid to fluidized bed. The objective of this study is to investigate the possibility of using cashew nut shale waste as an alternative adsorbent for the removal of arsenic (III) ions from aqueous solutions by using gas–liquid–solid fluidized bed. The effect of gas velocity, liquid velocity, initial static bed height and average particle size on the adsorption of arsenic (III) by cashew nut shale waste is investigated using batch methods. The single and combined effects of operating parameters such as gas velocity, liquid velocity, initial static bed height and average particle size on the adsorption of arsenic (III) from wastewater are analyzed using response surface methodology (RSM). A 24 full factorial central composite experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2=0.9611) and satisfactory prediction second-order regression model was derived. The optimum operating conditions were determined as gas velocity, 12.5m/s; liquid velocity, 0.04m/s; initial static bed height, 0.1m and average particle size of 1.27mm. At optimum adsorption conditions, the adsorption of arsenic (III) from wastewater in a three phase fluidized bed is found to be 92.5464%.