SOLID PHASE EXTRACTION OF HEAVY METALS USING LOW COST SORBENTS

Abstract

The aim of present work is to investigate the sorption capacity of salvadora persica, activated carbon, chitosan and chemically modified chitosan for heavy metals from dilute solutions. Salvadora persica was converted into powdered form and characterized by using Infrared spectroscopy. It has various organic compounds and these compounds contain sulphur, oxygen and nitrogen in their skeletons and behave superbly as coordinating ligands for cations present in the aqueous solution and hence causing effective sorption. Activated carbon was also prepared from salvadora persica under vacuum at 673 K with different soacking time. The prepared activated carbons were characterized using Surface Area Analyzer. Percentage yield of the prepared activated carbons in different heating times prior to washing was different. The activated carbon yields obtained at 673 K were 54.78 %, 52.27 % and 50.31 % at 30, 45 and 60 min heating time, respectively. The yield of activated carbons decreased as the heating duration increased. Surface area decreased from 375 to 27 m2/g. 4-Acryloylmopholine was reacted with chitosan to alter it chemically .The aim of treatement was to enhance binding sites for heavy metals ions. The amended chitosan holds different binding sites (chelating centers) in the form of oxygen and nitrogen. Different techniques were applied to illustrate the amended chitosan. Activated carbons, powdered salvadora persica, chitosan and the chemically modified chitosan were used as sorbents for different cations (Cu 2+, Cd 2+, Pb 2+ and Ni 2+ ). Among these cations copper showed highest sorption ability as compared to other and the sorption properties were in agreement with that of the Langmuir model. The activated carbon prepared at 30 min heating time, showed maximum sorption capacities for cations due to its larger surface area. The Freundlich, Langmuir and Temkin models (both linear and non linear methods) were used to assess the experimental statistics. For activated carbon and powdered salvadora persica, lower errors were shown by type one (I) of the Langmuir model as compared to Freundlich and Temkin models, so it is the appropriate model to explain the sorption phenomenon. Among the linear forms of the Langmuir isotherms, low error values were given by type four (IV) than other linear forms of Langmuir and the Freundlich model but higher than that of Temkin model, which shows that Temkin model fits better to the experimental data of chemically modified chitosan.