Abstract:

In order to explore the high-value utilization of agricultural and forestry waste, six common types of agricultural and forestry waste, including corn stalks, rice straw, soybean stalks, pine branches, bamboo branches, and biogas residue, were used as raw materials to prepare biochar by limiting oxygen and temperature controlling carbonization in vacuum tube furnace. The physicochemical properties and structural characteristics of biochar were analyzed by surface area analyzer, scanning electron microscope and Fourier transform infrared spectroscopy, and the adsorption capacity of biomass carbon on ammonia nitrogen and total phosphorus in swine wastewater was investigated. The results showed that six kinds of biomass carbons were alkaline, and the alkalinity of biogas residue biochar was stronger than that of plant biochar. The yield order of six kinds of biochar was as following: biogas residue biochar(64.83%) > soybean stalk biochar(57.22%) > rice straw biochar(48.80%) > corn stalk biochar(46.87%) > bamboo biochar(41.42%) > pine branch biochar(40.01%). Among them, the soybean stalk biochar had a larger specific surface area(5.84 m²/g) and developed pores. All six kinds of biochar contained abundant oxygen-containing functional groups on their surfaces, and both chemically stable C—H and benzene rings had strong stability. The six kinds of biochar had certain adsorption effects on ammonia nitrogen and total phosphorus in aquaculture wastewater, with corresponding adsorption capacities ranging from 20.00 to 31.00 mg/g and 4.00 to 6.69 mg/g, respectively. Soybean stalk biochar had the best adsorption effect on ammonia nitrogen and total phosphorus, with a saturated adsorption capacity of 31.00 mg/g and 6.69 mg/g, respectively.

Key words: agricultural and forestry wastes, biochar, swine wastewater, ammonia nitrogen, total phosphorus