Utilization of Jujube Biomass to Prepare Biochar by Pyrolysis and Activation: Characterization, Adsorption Characteristics, and Mechanisms for Nitrogen

Abstract

The rapid advancement of jujube industry has produced a large amount of jujube biomass waste, requiring the development of new methods for utilization of jujube resources. Herein, medium-temperature pyrolysis is employed to produce carbon materials from jujube waste in an oxygen-free environment. Ten types of jujube biochar (JB) are prepared by modifying different pyrolysis parameters, followed by physical activation. The physicochemical properties of JB are systematically characterized, and the adsorption characteristics of JB for NO3− and NH4+ are evaluated via batch adsorption experiments. Furthermore, the pyrolysis and adsorption mechanisms are discussed. The results indicate that the C content, pH, and specific surface area of JB increase with an increase in the pyrolysis temperature from 300 °C to 700 °C, whereas the O and N contents, yield, zeta potential, and total functional groups of JB decrease gradually. The pyrolysis temperature more significantly effects the biochar properties than pyrolysis time. JB affords the highest adsorption capacity for NO3− (21.17 mg·g−1) and NH4+ (30.57 mg·g−1) at 600 °C in 2 h. The Langmuir and pseudo-second-order models suitably describe the isothermal and kinetic adsorption processes, respectively. The NO3− and NH4+ adsorption mechanisms of JB may include surface adsorption, intraparticle diffusion, electrostatic interaction, and ion exchange. In addition, π–π interaction and surface complexation may also be involved in NH4+ adsorption. The pyrolysis mechanism comprises the combination of hemicellulose, cellulose, and lignin decomposition involving three stages. This study is expected to provide a theoretical and practical basis for the efficient utilization of jujube biomass to develop eco-friendly biochar and nitrogenous wastewater pollution prevention.

Physicochemical and Optical Characterization of Citrus aurantium Derived Biochar for Solar Absorber Applications

“…XRD patterns also show the effect of temperature in the pyrolysis process where the peak at 44° is more evident in SOP800, which suggests that a higher temperature in the pyrolysis process produces a higher degree of carbonization, as was observed in the FTIR analysis and elemental analysis [ 43 ]. Finally, a sharp peak at 29.5° in SOP600 and SOP800 was observed—this peak can be related to the presence of inorganic components such SiO 2 and CaCO 3 , which suggests that with the increase of pyrolysis temperature, it produced a release of ash, for example, ashes contain alkali salts such as calcium carbonate [ 44 , 45 ].…”

“…In a similar way, the peak of K2p starts to appear in SOP400, which gradually increases and is more evident in SOP800. Both peaks are related to the presence of inorganic materials in the raw material and in the pyrolysis process and can be related to the ashes derived from the same process [ 44 ].…”

Computer Analysis of the Effect of Activation Temperature on the Microporous Structure Development of Activated Carbon Derived from Common Polypody

“…Carbonisation is achieved by heating the raw materials without the presence of air or in an inert gas atmosphere [ 22 ]. The physical activation process comprises a partial gasification of the carbonisation product at a temperature of 800–1000 °C with oxidising agents such as water steam or carbon dioxide; the use of a mixture of these agents is also possible [ 23 , 24 ]. The use of oxygen at a temperature below 800 °C is possible but is used less frequently.…”

Computer Analysis of the Porous Structure of Activated Carbons Derived from Various Biomass Materials by Chemical Activation

“…Activation processes are generally divided into two types—namely, physical and chemical activation [ 5 ]. Physical activation consists of partial gasification of the char with oxidising agents, e.g., water vapour or carbon dioxide at a temperature of 800–1000 °C, or, less frequently, oxygen at a temperature below 800 °C; the use of a mixture of these agents is also possible [ 6 , 7 , 8 ]. The reactions taking place in the process bring about the production of gaseous products and a gradual reaction of the carbonaceous substance, which is replaced with empty spaces known as pores, while the specific surface area of the material increases.…”

“…The reactions taking place in the process bring about the production of gaseous products and a gradual reaction of the carbonaceous substance, which is replaced with empty spaces known as pores, while the specific surface area of the material increases. Temperature has the highest impact on the course of the activation process; at relatively low temperatures, the rate of the chemical reaction of the char with the oxidising agent is low, as is the rate of the whole process [ 6 , 7 , 8 ].…”