REV. CHIM. (Bucharest) ♦ 65♦ No.7 ♦ 2014 http://www.revistadechimie.ro 750 Chitosan and Chitosan Modified with Glutaraldehyde Microparticles for Pb(II) Biosorption II. Equilibrium and kinetic studies CLAUDIA MARIA SIMONESCU 1 *, IRINA MARIN 1 , CHRISTU TARDEI 2 , MIOARA DRAGNE 3 , CAMELIA CAPATINA 4 1 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Analytical Chemistry and Environmental Engineering, 1 – 7 Polizu Str., 011061, Bucharest, Romania 2 National Institute for R&D in Electrical Engineering ICPE-CA, 313 Splaiul Unirii, 031066, Bucharest, Romania 3 SC KEMWATER CRISTAL SRL, 51 Muncii Str., 915200, Fundulea, Cãlãraºi, Romania 4 University „Constantin Brâncuºi” of Târgu-Jiu, Engineering Faculty, 3 Geneva Str., 210152, Târgu-Jiu, Gorj, Romania This paper presents a comparative study regarding the use of chitosan and cross-linked with glutaraldehyde (GLA) chitosan microparticles in the retention of Pb(II) ions from aqueous solutions with low Pb(II) levels. Initial Pb(II) ion concentration, contact time, and pH are parameters considered. Sorption capacity value reaches 43.78 mg Pb(II)·g -1 for chitosan particles, and 41.68 mg Pb(II)·g -1 for chitosan-GLA particles, respectively. Equilibrium sorption data for Pb(II) removal onto chitosan, and chitosan-GLA were consistent with the Langmuir isotherm. Kinetic parameters for the pseudo-first and pseudo-second orders and intraparticle diffusion equations were determined. Pb(II) sorption on chitosan microparticles can be expressed as a pseudo-second order kinetic which characterizes a chemical process. A different kinetic behaviour function of Pb(II) concentration was observed for chitosan-GLA microparticles. Results show that microparticles obtained can be successfully used for remediation of wastewater with low lead content. Keywords: chitosan microparticles, chitosan-GLA microparticles, lead removal from wastewater, equilibrium and kinetic studies * email: claudiamaria_simonescu@yahoo.com Water quality represents a major concern worldwide. Water effluents contaminated with heavy metals have been extensively studied due to their negative effects on natural ecosystems equilibrium and living organisms. The main sources of heavy metals pollution are: metal cleaning and plating facilities, mining, corrosion and electronic device manufacture, paints, battery manufactures, petroleum refining, fertilisers, leather industry [1, 2]. Among all heavy metals, special attention has given to lead due to its negative effects on humans such as mental retardation, kidney diseases, semi- permanent brain damage and many other symptoms [3- 5]. As a result, lead has to be removed from wastewater in order to prevent natural waters pollution. Many conventional treatment methods such as chemical precipitation, ion exchange, sorption, electrochemical technologies, and membrane separation were applied to remove lead from wastewaters [6-21]. All these methods show several disadvantages such as high operating costs, incomplete lead removal, low selectivity, inadequate for lead removal from wastewater with low lead level, and production of large quantities of wastes [22-25]. The most popular method for the removal of heavy metal from aqueous solutions is sorption using biomaterials. Several biomaterials like grape stalk waste [26], three wastes [27], the aquatic plant, Lemna perpusilla Torr. [28], ethylene- diamine-modified yeast biomass coated with magnetic chitosan microparticles (EYMC) [29], native and chemically treated olive stone [30] were used for lead removal from aqueous solutions. The use of natural biomaterials is a promising alternative due to their low cost and their relative abundance. The adsorption capacities of these adsorbents are dependent on the porosity, surface area-to-volume ratio, and number of active binding sites [31]. Polysaccharide biopolymers are mainly used as adsorbents of heavy metals from aqueous solutions. They are generally derived from agricultural or shell waste from crustaceans. Chitin is a biopolymer found in crustaceans, fungi, insects, annelids, molluscs and coelenterata [31]. Chitin abundance is second to cellulose and it is used to obtain chitosan by deacetylation. Metal ions chelating capacity of chitosan depends on chitin deacetylation degree. Increasing the deacetylation degree of chitin leads to the increasing of chitosan metal chelating capacity [32]. This property is related to the content of the amino groups in the polymer chain, and the degree of polymerisation of oligochitosan. The main disadvantages of use of chitosan for heavy metals removal from wastewaters are low porosity and its low stability in acidic media (pH<2) that determines inconveniencies in adsorbent removal from treated effluents. Physical and chemical modifications of chitosan are used to overcome this disadvantage. For this purpose, chitosan microparticles were previously obtained by physical modification of chitosan flakes. Chemically modified chitosan microparticles were obtained by cross- linking with GLA to improve its solubility in acidic media (pH<2) [33]. These microparticles previously obtained were characterized and tested for resistance against acid, alkali and other chemicals [33]. Results obtained showed that physical modification of chitosan flakes has as results improving the mechanical strength, and chemical modification enhances its resistance against acid solutions.