Adsorption Isotherm and Thermodynamic Profile of Hexavalent Chromium onto Lumbang (Aleurites moluccana) Activated Carbon Chitosan Composite Crosslinked with Epichlorohydrin
Nelson R. Villarante
Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila, Manila, Philippines.
Angelo Patrick R. Bautista
Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila, Manila, Philippines.
Derick Erl P. Sumalapao *
Department of Biology, College of Science, De La Salle University, Manila, Philippines and Department of Medical Microbiology, College of Public Health, University of the Philippines Manila, Manila, Philippines.
*Author to whom correspondence should be addressed.
Abstract
Adsorption isotherm and thermodynamic profile of hexavalent chromium onto lumbang (Aleurites moluccana) activated carbon chitosan composite crosslinked with epichlorohydrin were studied. The optimum conditions were identified at pH 3, contact time of 75 min, adsorbent dose of 3 g/L, initial concentration of 60 ppm, and 30ºC temperature resulted to a removal efficiency of 93%. The composite has a round and elliptical adsorption sites, contains –OH and –NH2 functional groups, and has increased stability with epichlorohydrin crosslinking. The adsorption process is best characterized by the Langmuir isotherm suggesting a monolayer adsorption nature of Cr(VI). The adsorption kinetics obeyed the pseudo-second order model and the adsorption process is exothermic. The investigated adsorption phenomenon described a chemisorption process, with 21.32 kJ mol-1 mean free energy, due to the functional groups identified and the high porosity of the adsorbent surfaces.
Keywords: Adsorption isotherm, thermodynamics, carbon chitosan composite, chromium, lumbang, Aleurites moluccana.