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

Abstract

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.

One-Step Carbonization Synthesis of Magnetic Biochar with 3D Network Structure and Its Application in Organic Pollutant Control

“…On the contrary, the correlation coefficients ( R 2 ) of the PSK were 0.9949–0.9996 and 0.9966–0.9991 for BMFH and BMFH/Fe 3 O 4 , respectively, when the adsorbate was MG, and 0.9986–0.9998 and 0.9990–0.9999, respectively, when the adsorbate was TH. At the same time, the q e.cat values calculated theoretically according to PSK were more suitable for the experimental quantification q e , indicating the applicability and potential advantages of Ho–McKay’s model in the adsorption process; that is, the adsorption rate may be controlled by chemical reactions, and similar reactions that form chemisorption bonds between adsorbent and adsorbent through transfer, exchange, or sharing can promote the adsorption process [ 23 , 24 , 25 , 26 , 27 ]. For the IPD model, the correlation coefficients ( R 2 ) were 0.7582–0.9050 (MG) and 0.7178–0.8271 (TH) for BMFH and 0.7824–0.8741 (MG) and 0.7341–0.8163 (Th) for BMFH/Fe 3 O 4 , demonstrating that the IPD model was not able to explain the whole adsorption process.…”

“…The functional groups of the samples were analyzed by FT-IR, as shown in Figure 3 A. The wide band corresponding to the stretching vibration of the hydroxyl functional group at a range of 3400–3500 cm −1 indicates that a large number of oxygen-containing functional groups [ 23 , 24 , 25 , 26 , 27 ] exist on all samples. In the range of 2800–2900 cm −1 , symmetric and asymmetric tensile vibration peaks of -CH groups were found [ 30 , 31 ], which may be caused by the thermal cracking of macromolecules from FH at high temperature and the removal of a large amount of hydrogen [ 31 , 34 ].…”

“…The high-resolution O1s spectrum of the BMFH ( Figure 5 C) and BMFH/Fe 3 O 4 -0.01 ( Figure 5 F) showed three peaks, including the quinones at approximately 530.10 ± 0.22 eV, C=O at approximately 531.21 ± 0.18 eV, and C-O at approximately 532.55 ± 0.10 eV [ 24 , 26 ]. The high-resolution N1s spectrum of the BMFH ( Figure 5 D) and BMFH/Fe 3 O 4 -0.01 ( Figure 5 G) showed two peaks: pyridinic-N at approximately 398.64 ± 0.30 eV and pyrrolic-N at approximately 400.32 ± 0.02 eV [ 27 ]. The high-resolution Fe 2p spectrum of BMFH/Fe 3 O 4 -0.01 ( Figure 5 H) showed three peaks: Fe 2p 3/2 corresponding to 711.02 eV, Fe 2p 1/2 corresponding to 724.28 eV, and shakeup satellite peak at approximately 716.04 eV, which revealed the characteristic peaks of Fe in Fe 3 O 4 [ 25 ].…”

“…Temperature is an important parameter affecting the adsorption process. On the one hand, it can promote the thermal movement of molecules in the reaction system, and on the other hand, it can directly affect the endothermic or exothermic reaction through the thermal energy [ 27 ]. The thermodynamic parameters standard entropy (Δ S ), standard Gibbs free energy (Δ G ), and standard enthalpy (Δ H ) were analyzed to study the adsorption process.…”

“…In order to pursue the extreme performance of materials so as to better cope with water security crises, many scientists have developed a large number of materials with unique structures and excellent performance [ 23 , 24 ]. Among many advanced materials, biochar has received much attention because of its attractive structure, huge specific surface area, rich functional groups, and so on [ 25 , 26 , 27 ]. In general, the characteristics and properties of biochar often determine its application.…”