title: Coupled factors influencing detachment of nano- and micro-sized particles from primary minima.
abstract: This study examined the detachments of nano- and micro-sized colloids from primary minima in the presence of cation exchange by laboratory column experiments. Colloids were initially deposited in columns packed with glass beads at 0.2 M CaCl(2) in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Then, the columns were flushed with NaCl solutions with different ionic strengths (i.e., 0.001, 0.01, 0.1 and 0.2 M). Detachments were observed at all ionic strengths and were particularly significant for the nanoparticle. The detachments increased with increasing electrolyte concentration for the nanoparticle whereas increased from 0.001 M to 0.01 M and decreased with further increasing electrolyte concentration for the micro-sized colloid. The observations were attributed to coupled influence of cation exchange, short-range repulsion, surface roughness, surface charge heterogeneity, and deposition in the secondary minima. The detachments of colloids from primary minima challenge the common belief that colloid interaction in primary minimum is irreversible and resistant to disturbance in solution ionic strength and composition. Although the significance of surface roughness, surface charge heterogeneity, and secondary minima on colloid deposition has been widely recognized, our study implies that they also play important roles in colloid detachment. Whereas colloid detachment is frequently associated with decrease of ionic strength, our results show that increase of ionic strength can also cause detachment due to influence of cation exchange.
authors.affiliation: Key Laboratory of Plant-Soil Interactions, Ministry of Education of the People's Republic of China, Department of Soil and Water Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Chongyang
authors.initials: C
authors.lastname: Shen
authors.forename: Volha
authors.initials: V
authors.lastname: Lazouskaya
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.forename: Baoguo
authors.initials: B
authors.lastname: Li
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Ma
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Zheng
authors.forename: Yuanfang
authors.initials: Y
authors.lastname: Huang
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D009994:Osmolar Concentration; D010087:Oxides / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D012965:Sodium Chloride; D012972:Sodium Hydroxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D017610:Calcium Compounds; D002412:Cations; D003102:Colloids; D010087:Oxides; D011137:Polystyrenes; D012965:Sodium Chloride; C004569:soda lime; D012972:Sodium Hydroxide; C024075:styrofoam