title: [Adsorption of calcium ion from aqueous solution using Na(+)-conditioned clinoptilolite for hot-water softening].
abstract: This work investigated adsorptive removal of calcium ion (Ca2+) by virtue of Na(+) -conditioned clinoptilolite simulating the process of softening for industrial hot-water system. Influential factors such as the activation/regeneration of sorbent and solution pH were tested. The kinetics/thermodynamics for adsorption of Ca2+ were analyzed and discussed. Results showed that: (1) The adsorption rate was in good agreement with the pseudo-second order kinetic models, and the process of adsorption better followed the Langmuir model; (2) Higher solution temperature allowed an enhanced efficiency on Ca2+ removal, albeit the maximum adsorption capacity of Na(+)-conditioned clinoptilolite was hardly affected; (3) The process of adsorption was dominated by chemisorption, and also characterized by entropy increase with spontaneous/endothermic nature; (4) Solution temperature was suggested to be controlled within the range of 6 to 10, and more than 9 times of sorbent regeneration could be ensured for an effective adsorption towards Ca2+ with initial concentration less than 20 mg x L(-1). It was demonstrated that the activated clinoptilolite should be a promising alternative adsorbent for industrial hot-water softening.
authors.forename: Shuo
authors.initials: S
authors.lastname: Zhang
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.forename: Yuan-Chao
authors.initials: YC
authors.lastname: Chen
authors.forename: Xing-Wen
authors.initials: XW
authors.lastname: Zhang
authors.forename: Gui-Jun
authors.initials: GJ
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D002118:Calcium / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D014867:Water; D014874:Water Pollutants, Chemical; D018508:Water Purification; D014880:Water Softening / Q000379:methods*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D007477:Ions; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; C083175:clinoptilolite; D017641:Zeolites; D002118:Calcium