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.
Highlights
The jujube (Ziziphus jujuba Mill., 1768) tree is widely distributed in southern and eastern Asia, Europe, Americas, and Australia [1], and can be a valuable resource of biomass energy owing to its high heating value and environmental resilience [2]
The total content of jujube biochar (JB) surface functional groups decreases with an increase in the pyrolysis temperature
When the temperature is higher than 600 ◦ C, the change of TG and derivative thermogravimetric (DTG) curves tended to be flat and almost straight, indicating that the jujube biomass was completely pyrolyzed and the structure was rearranged, and the type of material was dominated by messy amorphous carbon
Summary
The jujube (Ziziphus jujuba Mill., 1768) tree is widely distributed in southern and eastern Asia, Europe, Americas, and Australia [1], and can be a valuable resource of biomass energy owing to its high heating value and environmental resilience [2]. A large amount of jujube branches are discarded during pruning and metabolisms due to the lack of innovative product development technologies, and the utilization of jujube biomass is very low in many areas [4,5]. Because of the excessive application of artificial fertilizer in agricultural production, nitrogen is not completely utilized and absorbed, causing non-point source pollution that in turn leads to water eutrophication and groundwater pollution [25]. This outcome endangers the health of humans and growth of plants and animals, and decreases the quality of water resources and increases the cost of their remediation [26]. The adsorption of NO3 − and NH4 + on JB was analyzed by batch adsorption experiments, and the pyrolysis and adsorption mechanisms were elucidated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
