Characterization of High-Performance Zinc Chloride Activated Biochar Modified by Thermal Chemical Vapor Deposition (CVD) and Its Removal Mechanism of Aqueous Nitrate Ions

摘要

Although zinc chloride (ZnCl2) has been a well-known efficient activate agent for char, there are few precedents that biochar can efficiently remove nitrate ions with a high adsorptive capacity from aqueous solution. In this study, an efficient biomass (bamboo) activated carbon was developed by ZnCl2 activation. Lignin removed Moso bamboo was activated by 3 times mass ratio of ZnCl2, followed by 500 celcius pyrolysis for 1 h, named BZ3. For improving the adsorption capacity of BZ3 for nitrate ions, thermal chemical vapor deposition (CVD) was used to treat BZ3 for optimizing the surface structure. Among the tested procedures, the sample treated by the order of an acetonitrile vapor doping nitrogen at 800 celcius, then 950 celcius heating for 30 min followed by steam treatment at 800 celcius was proven the most high-spec sample. The obtained activated biochar was proven as BZ3-8AN20-9.5HT30-8ST30. It showed the maximum nitrate adsorption capacity of 0.57 mmol/g in nitrate concentration of 200 mg/L at solution pH 3 with the surface area 900 m(2)/g, tested by Brunauer-Emmett-Teller method. In the weak acidic to weak alkali solution pH range 6-8, the adsorption capacity of 0.28 mmol/g on BZ3-8AN20-9.5HT30-8ST30 was higher than that of BZ3-8AN20-8ST30. For the kinetic test, BZ3-8AN20-9.5HT30-8ST30 could fit to both pseudo-first-order (R-2 = 0.957) and pseudo-second-order well (R-2 = 0.993).