Cow Dung-Based Biochar Materials Prepared via Mixed Base and Its Application in the Removal of Organic Pollutants

Cow dung (CD) is a waste product of livestock production. Improper disposal of a large amount of CD will cause environmental pollution. In this work, three biochar materials based on CD (BMCD) were prepared by using three types of base, including KOH, NaOH, and mixed base (MB, a mixture of equal mass NaOH and KOH) as activators to investigate the different physicochemical properties of BMCDs (BMCD-K, BMCD-Na, and BMCD-MB). The objective was to verify the effectiveness of MB activation in the preparation of biochar materials. The results show that MB has an effect on the structural characteristics of BMCDs. In particular, the surface area and total pore volume, the specific surface area, and the total pore volume of BMCD-MB (4081.1 m² g^-1 and 3.0118 cm³ g^-1) are significantly larger than those of BMCD-K (1784.6 m² g^-1 and 1.1142 cm³ g^-1) and BMCD-Na (1446.1 m² g^-1 and 1.0788 cm³ g^-1). While synthetic dye rhodamine B (RhB) and antibiotic tetracycline hydrochloride (TH) were selected as organic pollutant models to explore the adsorption performances, the maximum adsorption capacities of BMCD-K, BMCD-NA and BMCD-MB were 951, 770, and 1241 mg g^-1 for RhB, 975, 1051, and 1105 mg g^-1 for TH, respectively, which were higher than those of most adsorbents. This study demonstrated that MB can be used as an effective activator for the preparation of biochar materials with enhanced performance.