One-Step Pyrolysis of Nitrogen-Containing Chemicals and Biochar Derived from Walnut Shells to Absorb Polycyclic Aromatic Hydrocarbons (PAHs)

Abstract

The pyrolysis of biomass is an efficient means of utilizing biomass resources. Biomass can be converted into various high-performance chemicals and functional materials through pyrolysis. However, current pyrolysis technologies suffer from low conversion rates and single products, so the preparation of nitrogen compounds with high economic value remains a challenge. The walnut shell was soaked in three nitrogen-containing compound solutions before carbonization to produce high-value-added nitrogen-containing chemicals (with a nitrogen content of 59.09%) and biochar for the adsorption of polycyclic aromatic hydrocarbons (PAHs). According to biochar analysis, biochar has a porous structure with a specific surface area of 1161.30 m2/g and a high level of rocky desertification. The surface forms a dense pyrrole structure, and the structure produces π–π interactions with naphthalene molecules, exhibiting excellent naphthalene adsorption with a maximum capacity of 214.98 mg/g. This study provides an efficient, rapid, and environmentally friendly method for producing nitrogen-containing chemicals with high-added value and biochar.

Adsorptive Performance of Walnut Shells Modified with Urea and Surfactant for Cationic Dye Removal

“…Few research publications exist on the urea treatment of walnut shells. These studies show that combined urea-acid modification of raw walnut shells is efficient for synthetic dye sorption [15], and carbonized walnut shells N-doped by urea show a very promising results for CO 2 [16][17][18], naphthalene [19] and perchloroethylene [20] adsorption.…”

Preparation of Biomass Biochar with Components of Similar Proportions and Its Methylene Blue Adsorption

“…These are the characteristic absorption peaks of two typical type I lignocelluloses: the former corresponds to the noncrystalline area of cellulose, and the latter is the 101/002 diffraction absorption peak of the crystalline area of cellulose. Some of the crystalline areas in walnut green husk were converted into noncrystalline areas, which increased the number of adsorption sites and helped improve its adsorption capacity [24]. Diffraction peaks appeared near 2θ = 22.1 • , 26.1 • , 50 • , etc., in the spectrum of SBB, corresponding to oxides of elemental Si in the biochar; diffractograms showing diffraction lines indicating the presence of silica (quartz), alumina, calcium oxide, magnesium oxide, iron trioxide, and potassium oxide [25,26], which disappear after CO 2 activation, have been reported.…”