title: Adsorptive removal of Pb2+ form aqueous solution by macrocyclic calix[4]naphthalene: kinetic, thermodynamic, and isotherm analysis.
abstract: BACKGROUND
  The adsorption characteristics of Pb(2+) ions from aqueous solutions onto calix[4]naphthalene have been investigated.
  
  
  METHODS
  Calix[4]naphthalene was prepared by the condensation of 1-naphthol and formaldehyde (1:2) in presence of hydrochloric acid at 80 °C. The effect of various operation parameters, such as solution pH, initial metal ion concentration, contact time, and temperature, on the adsorption capacity of calix[4]naphthalene for Pb(2+) have been investigated.
  
  
  RESULTS
  Experimental results showed that the adsorption of Pb(2+) ions increased with the increase in solution pH and temperature. Langmuir and Freundlich isotherms models were used to describe the adsorption behavior of Pb(2+) by calix[4]naphthalene. Equilibrium data fitted well with the Langmuir isotherm model and the maximum adsorption capacity of calix[4]naphthalene for Pb(2+) at 30 °C was found to be 29.15 mg g(-1). Kinetic studies indicated that the adsorption followed pseudo-second order model and the thermodynamic studies revealed that the adsorption process was spontaneous and endothermic in nature. The obtained results demonstrated that calix[4]naphthalene can be used as an effective adsorbent for Pb(2+) ions removal from water.
authors.affiliation: Environmental Research Laboratory, Department of Applied Chemistry, Aligarh Muslim University, Aligarh 202002, India.
authors.forename: Rais
authors.initials: R
authors.lastname: Ahmad
authors.forename: Rajeev
authors.initials: R
authors.lastname: Kumar
authors.forename: Mohammad Asaduddin
authors.initials: MA
authors.lastname: Laskar
mesh_terms: D000327:Adsorption; D007477:Ions; D007700:Kinetics; D007854:Lead / Q000032:analysis* / Q000737:chemistry; D009281:Naphthalenes / Q000032:analysis* / Q000737:chemistry; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D007477:Ions; D009281:Naphthalenes; D014874:Water Pollutants, Chemical; C031721:naphthalene; D007854:Lead