Recycled chitosan nanofibril as an effective Cu(II), Pb(II) and Cd(II) ionic chelating agent: Adsorption and desorption performance

Highlights

• Nanofibrillar chitosan exhibited cross-linked and multi-porous networks.

• q_max of heavy metal ions loaded by nanofibrils was much higher than reported chitosan sorbents.

• Nanofibrils could be recycled at about 80% recovery level after three sorption–desorption cycles.

• Cu(II) was the most competitive ions to be chelated by nanofibrils.

Abstract

Mechanically disassembled chitosan nanofibrils were prepared and used as metal ion chelating agents. Structure and morphology of nanofibrils were investigated and ionic adsorption or desorption performance were validated to establish related fitting models. In single metal ion solution, the saturated adsorption capacities of Cu(II), Pb(II), Cd(II), Zn(II), and Ni(II) were 168.66, 118.00 and 60.85, 143.67, and 63.32 mg/g, respectively. In ternary metal ion solution, Cu(II) was more competitive to be adsorbed than Pb(II) and Cd(II) and its removal could arrive at 60%. Ions adsorbed by nanofibrils could be released by EDTA and the recovery could keep above 70% after 3 sorption–desorption cycles. Hence, renewable and recyclable nanofibrillar chitosan exhibited a great promising application in metal treatments attributed to its high adsorption capacity and chelation efficiency.

Introduction

Heavy metals or transition metals emanated from chemical industries are transferred and enriched in water or soil environments (Jeon and Ha Park, 2005, Wang et al., 2010), whereas bring serious problems to living beings (Deng, Liu, Zeng, Qiu, & Li, 2013). Renewable natural resources have been gaining prominence as effective and economical biosorbents to remove toxic metal ions from aqueous environment (Laus and de Fávere, 2011, Muzzarelli, 2011), since these cost-effective adsorbents are known to have high binding capacity on metal ions (Jeon & Ha Park, 2005; Muzzarelli & Sipos, 1971) and many other advantages such as low generation of residues, easy metal recovery, and the possibility of reuse. Chitosan, a partially deacetylated product of chitin, is soluble in acidic media and thereby produces a unique polycationic structure (Gamage and Shahidi, 2007, Popuri et al., 2009; Muzzarelli, Ferrero, & Pizzoli, 1972). It is well known that chitosan is very useful in the aqueous-phase separation of heavy metals (Chen et al., 2008, Muzzarelli, 1973, Wan Ngah et al., 2011).

Environmental fibrillar nanomaterial is one of the most important research topics in recent years due to their interesting characteristics, such as fine diameters (ranging from submicron to several nanometers), large surface area per unit mass, wide-range porosity, high gas permeability, and small interfibrous pore size (Haider and Park, 2009, Liu et al., 2011a, Muzzarelli, 2012). In our former reports, we established a joint mechanical method to defibrillate chitosan or chitin particles into nanofibrils (Liu, Wu, Chang, & Gao, 2011). In continuation with the earlier studies on chitin nanofibrillar adsorbents (Liu, Zhu, et al., 2013), the chitosan nanofibrils was isolated and used as chelating agents of Cu(II), Pb(II) and Cd(II) ions in this work. The adsorption and desorption performance in single and ternary metal ion system was investigated. We tried to provide some meaningful information about this novel chelating agent by predicting the nature of the adsorption and desorption process for further engineering application in metal pollutant treatments.