Abstract
According to its characteristics, biochar originating originating from biomass is accepted as a multifunctional carbon material that supports a wide range of applications. With the successfully used in reducing nitrate and adsorbing ammonium, the mechanism of biochar for nitrogen fixation in long-term brought increasing attention. However, there is a lack of analysis of the NH4+-N adsorption capacity of biochar after aging treatments. In this study, four kinds of acid and oxidation treatments were used to simulate biochar aging conditions to determine the adsorption of NH4+-N by biochar under acidic aging conditions. According to the results, acid-aged biochar demonstrated an enhanced maximum NH4+-N adsorption capacity of peanut shell biochar (PBC) from 24.58 to 123.28 mg·g−1 after a H2O2 modification. After the characteristic analysis, the acid aging treatments, unlike normal chemical modification methods, did not significantly change the chemical properties of the biochar, and the functional groups and chemical bonds on the biochar surface were quite similar before and after the acid aging process. The increased NH4+-N sorption ability was mainly related to physical property changes, such as increasing surface area and porosity. During the NH4+ sorption process, the N-containing functional groups on the biochar surface changed from pyrrolic nitrogen to pyridinic nitrogen, which showed that the adsorption on the surface of the aged biochar was mainly chemical adsorption due to the combination of π-π bonds in the sp2 hybrid orbital and a hydrogen bonding effect. Therefore, this research establishes a theoretical basis for the agricultural use of aged biochar.
Highlights
Excessive fertilization is one of the main reasons for low nutrient use efficiency, which may lead to the high risk of non-point source pollution, especially in intensive vegetable cultivation areas [1,2]
The surface area and pore volume of the micropores were measured with the CO2 gas method and calculated by the density functional theory (DFT) method, while the other pore structures were measured by the N2 gas method and calculated by the BJH method [41]
Hydrogen peroxide-aged biochar had the highest amount of NH4 + -N (123.23 mg·g−1 ) sorption among the five kinds of prepared biochar
Summary
Excessive fertilization is one of the main reasons for low nutrient use efficiency, which may lead to the high risk of non-point source pollution, especially in intensive vegetable cultivation areas [1,2]. In China, the yield of commercial vegetables mostly depends on the application of a high quantity of nitrogen fertilizer. Long-term fertilization application, the overuse of nitrogen fertilizers, has caused nitrogen discharge from farmland into underground water and the aquatic ecological system, which has been confirmed to be the main reason for eutrophication and has further resulted in both soil and water quality deterioration. Nitrogen leaching leads to the loss of soil fertility and causes damage to the environment and human health [4,5,6]. When the rate of nitrogen fertilizer application exceeds the nitrogen requirement of a plant for a long time, it will cause the accumulation of ammonium nitrogen
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