Preparation And Performances Of Modified Cellulosic Material For Cd²⁺ And Pb²⁺ Adsorption From Aqueous Solutions

Heavy metal pollution inflicts adverse effects on organisms and humans and is considered a global environmental issue. Heavy metals such as cadmium(Cd²⁺) and lead(Pb²⁺) are among the most common pollutants found in industrial effluents. Conventional methods employed for the removal of heavy metals fr om effluents mainly include chemical precipitation, ion exchange, membrane separation, reverse osmosis, and electrolysis. Most of these methods are costly or ineffective. Adsorption is considered to be one of the most convenient and cost-efficient methods. Conventional adsorbents such as activated carbon and synthetic nano-particles are costly or nonrenewable. Recently, natural materials have attracted increasing attention as adsorbents for heavy metals because of their abundant availability and renewable properties.In this study, dewaxed cornstalk?LCM? was chemically modified with NTAA which has shown excellent metal binding properties, and the characteristics of the novel material NTAA-LCM were analyzed. Also, the adsorption behavior of NTAA-LCM for Cd²⁺ and Pb²⁺ from aqueous solutions was evaluated by batch tests, and the interaction mechanisms between metals and NTAA-LCM were explored. Three parts was involved in this paper as the following:The first part was the preparation and characterization of the novel adsorbent. In order to improve the synthesis yield of NTAA-LCM, we optimized the modification time and the LCM/NTA ratio by two steps. As a result, the optimal immobilization condition was conducted at: reaction time 20 h and LCM/NTA ration 1:9. Elemental analysis showed that 0.797 mmol of NTA was present in 1 g of the resultant NTAA-LCM. Additionally, FTIR and XRD characterization further suggested that LCM was successfully immobilized by NTA.The effects of reaction time and pH on the sorption of metals by LCM were studied in the second part. Also, desorption behavior was studied. The sorption was first fast and then became slow, and the equilibrium adsorption capacity of LCM was 15.1 mg/g and 29.6 mg/g for Cd²⁺ and Pb²⁺, respectively. The solution pH influenced on the adsorption significantly. In addition, the desorption experiment suggested that the adsorption of metals by LCM might be physical process.In the third part, batch sorption experiments were performed to evaluate the influences of various factors such as contact time, pH, ionic strength, temperature and initial metal concentration on the sorption of metals. Fast adsorption rates were observed, and the maximum sorption capacities of NTAA-LCM for Cd²⁺ and Pb²⁺ reached 143.4 and 303.5 mg/g at 298 K, respectively. Both the pseudo-second-order model and the Langmuir model described the adsorption extremely well. Thermodynamic analysis showed that the sorption was endothermic but spontaneous. NTAA-LCM retained high metal sorption capacity after seven cycles of regeneration by HNO3. Additionally, the sorption was a chemical process involving surface chelation and ion exchange; this was reflected in the metal/NTA ratio.In the whole, a novel chelating material NTAA-LCM was synthesized in this article. NTAA-LCM showed excellent adsorption capacity, and it can be used as a promising adsorbent to remove heavy metals from acidic aqueous solution.