Preparation Of Cellulose Nanocrystals Based Adsorbent For The Adsorption Of Heavy Metals From Aqueous Solution

Nowadays, heavy metal pollution become a prominent issue of environmental pollution. Heavy metal pollution of water will not only resulting economic losses, but also bring huge threat to the ecological environment and life. So find fast and efficient methods of removing heavy metals, improve water quality is still a very important research direction. In this paper, we extracted cellulose nanocrystals?CNC? from microcrystalline cellulose?MCC?, and synthesized two new composites based on carboxylated cellulose nanocrystals?CCN?. Then, the materials were tested for its ability to adsorption of Pb??? and Cr??? from aqueous solution. The main contents and results are as following:?1? Cellulose nanocrystals extracted from microcrystalline cellulose was modified by citric acid, then used for the adsorption of Pb??? from fish sauce. Batch experiments were carried out to investigate the effect of contact time, initial concentration of Pb???, temperature, sodium chloride and amino acid concentration on Pb??? adsorption. The results showed that Pb??? adsorption on CCN reached equilibrium in 48 h. The maximum adsoption capacity of experiment was 149.59±2.33 mg/g at an initial concentration of 50 mg/L and adsorbent dosage of 0.1 g in 500 mL. Sodium chloride and glutamic acid would inhibit the adsorption of Pb??? from fish sauce. The equilibrium data fitted Langmuir isotherm better than Freundlich isotherm, and they were well explained by pseudo-second-order kinetic model. Thermodynamic studies indicated that the adsorption of Pb??? onto CCN was spontaneous and endothermic in nature.?2? Carboxylated cellulose nanocrystals?CCN? and polyethyleneimine?PEI? composite adsorbent?CCN-PEI? was prepared as adsorbent for the adsorption of Cr??? from aqueous solution. Batch experiments were carried out to investigate the effect of contact time, pH, initial concentration of Cr??? and temperature on Cr??? adsorption. The results showed that Cr??? adsorption on CCN-PEI reached equilibrium in 240 min. The maximum adsoption capacity of experiment was 243.39±2.67 mg/g at an initial concentration of 100 mg/L, pH 3 and adsorbent dosage of 0.005 g in 50 mL. The equilibrium data fitted Langmuir isotherm better than Freundlich isotherm, and they were well explained by pseudo-second-order kinetic model. Thermodynamic studies indicated that the adsorption of Cr??? onto CCN-PEI was spontaneous and exothermic in nature.?3? A novel magnetic cellulose nanocrystal?CCN-Fe₃O₄? was prepared as adsorbent for the adsorption of Pb??? from aqueous solution. Batch experiments were carried out to investigate the effect of contact time, adsorbent dose, pH, initial concentration of Pb??? and temperature on Pb??? adsorption. The results showed that Pb??? adsorption on CCN-Fe₃O₄ reached equilibrium in 240 min. The maximum adsoption capacity of experiment was 49.35±0.38 mg/g at an initial concentration of 50 mg/L, pH 5 and adsorbent dosage of 0.05 g in 50 mL. The equilibrium data fitted Langmuir isotherm better than Freundlich isotherm, and they were well explained by pseudo-second-order kinetic model. Thermodynamic studies indicated that the adsorption of Pb??? onto CCN-Fe₃O₄ was spontaneous and endothermic in nature.?4? The obtained materials were characterizated by fourier-transform infrared spectroscopy?FT-IR?, scanning electron microscopy?SEM?, transmission electron microscopy?TEM? and X-ray photoelectron spectroscopy?XPS?. And the adsorption mechanism of heavy metal ions adsorption onto the adsorbents were revealed.