Lignin microspheres: An effective and recyclable natural polymer-based adsorbent for lead ion removal

An increased interest in development of natural polymer-based sorbent for cleanup of heavy metals in water has been seen due to their abundance, low-in cost, and eco-friendliness. Lignin, the second most abundant natural polymer next to cellulose, however, is much limited by low response rate and low adsorption capability to heavy metals. Here, we show a new type of lignin microspheres (LMS) prepared by an inverse suspension copolymerization method for effective removal of Pb(II) in water. The prepared LMS was in diameter of 348 mu m with a large surface area of 9.6 m(2)/g, 5.3 times of lignin, and contained abundant amine functional groups (total N: 7.5 mmol/g). LMS showed a fast response rate and a high adsorption capacity to Pb(II) (33.9 mg/g), 137% and 280% larger than alkaline lignin and poplar lignin, respectively. The adsorption process was endothermic and spontaneous in nature. Moreover, the lead-loading LMS could be easily regenerated with a high adsorption stability, after five adsorption-desorption cycles, the adsorption capacity only decreased by 12.5%. The proposed LMS is eco-friendly, cost-effective and therefore a promising candidate for Pb(II) retention with effective adsorption and reusable abilities. (C) 2016 Elsevier Ltd. All rights reserved.