Influence Exerted by Cross-Linking Effect on Properties of Sorbents Produced from Aspen and Larch Bark

Abstract

Method is suggested for obtaining biochar materials by treatment of a finely dispersed (≤0.1 mm) bark of aspen and(or) larch with a 40% formaldehyde solution and subsequent thermal activation of the activated bark. It was found that keeping the composite at a temperature of 50–80°C for three days makes the binding process complete. Further carbonization at temperatures of 350–900°C yields a biochar with bulk structure. The method of IR spectroscopy confirmed that the functional composition of bark changes under the action of a cross-linking agent and — CH₂ — bonds are additionally formed. It was found that the larch bark containing lignins of predominantly G-type and condensed tannins is more suitable for obtaining porous biochar materials (with specific surface area of 94–161 m² g⁻¹) as compared with the aspen bark. The adsorption properties of biochar materials produced from the modified bark in removal of Cu(II) ions from aqueous solutions. It was found that, on being carbonized at 900°C, a sample of modified aspen bark can extract 122.9 to 220 mg g⁻¹ of copper compounds on raising the sorption temperature from 25 to 45°C.