Sorption-Desorption Hysteresis of Cd and Pb on Alluvial Soils as Affected by Clay Content

Document Type : Original Article

Abstract

ADSORPTION hysteresis in natural sorbents has important …….environmental implications for pollutant transport and bioavailability. The objective was to assess and compare the competitive adsorption and desorption capacities and adsorption hysteresis of Cd2+and Pb2+on four natural soils with different clay contents (10%, 20%, 40% and 50%, hereafter referred to S10, S20, S40 and S50) in terms of their physical and chemical properties. The adsorption-desorption hysteresis of Cd2+and Pb2+ were characterized using linear, Freundlich and Langmuir equations. In all soils Pb2+ was invariably sorbed and retained to a greater extent than Cd2+. Based on hysteresis index, Pb2+ was less mobile than Cd2+ in the studied soils. The adsorption and retention of Cd2+ and Pb2+were most influenced by pH, cation exchange capacity (CEC), total amorphous material percent (TAM%), total organic carbon percent (TOC%) and clay content. In all the soils Cd2+ exhibited greater hysteresis than Pb2+. The amounts of Cd2+ and Pb2+ desorbed from S10 were more than from S50, indicating that S50 was a more effective sorbent for water and wastewater treatment and clay content was the individual soil property most markedly influencing Cd2+ and Pb2+ adsorption and retention.
 
Keywords: Hysteresis, Adsorption, Desorption, Heavy metals.
 
DSORPTION hysteresis in natural sorbents has important …….environmental implications for pollutant transport and bioavailability. The objective was to assess and compare the competitive adsorption and desorption capacities and adsorption hysteresis of Cd2+and Pb2+on four natural soils with different clay contents (10%, 20%, 40% and 50%, hereafter referred to S10, S20, S40 and S50) in terms of their physical and chemical properties. The adsorption-desorption hysteresis of Cd2+and Pb2+ were characterized using linear, Freundlich and Langmuir equations. In all soils Pb2+ was invariably sorbed and retained to a greater extent than Cd2+. Based on hysteresis index, Pb2+ was less mobile than Cd2+ in the studied soils. The adsorption and retention of Cd2+ and Pb2+were most influenced by pH, cation exchange capacity (CEC), total amorphous material percent (TAM%), total organic carbon percent (TOC%) and clay content. In all the soils Cd2+ exhibited greater hysteresis than Pb2+. The amounts of Cd2+ and Pb2+ desorbed from S10 were more than from S50, indicating that S50 was a more effective sorbent for water and wastewater treatment and clay content was the individual soil property most markedly influencing Cd2+ and Pb2+ adsorption and retention.
 
 

Keywords