Oyster Shell Modified Tobacco Straw Biochar: Efficient Phosphate Adsorption at Wide Range of pH Values

Abstract

In order to improve the phosphate adsorption capacity of Ca-loaded biochar at a wide range of pH values, Ca (oyster shell) was loaded as Ca(OH)2 on the tobacco stalk biochar (Ca-BC), which was prepared by high-temperature calcination, ultrasonic treatment, and stirring impregnation method. The phosphorus removal performance of Ca-BC adsorption was studied by batch adsorption experiments, and the mechanism of Ca-BC adsorption and phosphorus removal was investigated by SEM-EDS, FTIR, and XRD. The results showed that after high-temperature calcination, oyster shells became CaO, then converted into Ca(OH)2 in the process of stirring impregnation and had activated the pore expansion effect of biochar. According to the Langmuir model, the adsorption capacity of Ca-BC for phosphate was 88.64 mg P/g, and the adsorption process followed pseudo-second-order kinetics. The Ca(OH)2 on the surface of biochar under the initial pH acidic condition preferentially neutralizes with H+ acid-base in solution, so that Ca-BC chemically precipitates with phosphate under alkaline conditions, which increases the adsorption capacity by 3–15 times compared with other Ca-loaded biochar. Ca-BC phosphate removal rate of livestock wastewater (pig and cattle farms) is 91~95%, whereas pond and domestic wastewater can be quantitatively removed. This study provides an experimental basis for efficient phosphorus removal by Ca-modified biochar and suggesting possible applications in real wastewater.

Adsorption properties of Pb(II) and Cd(II) in acid mine drainage by oyster shell loaded lignite composite in different morphologies

“…A large number of layered structures appear on the surface of OS-M(P), and some granular, mycelial and hexagonal structures are observed on the surface of OS-M(P) compared to lignite at 20 k magnification. According to the study of Khan et al 51 and Feng et al 52 , these granular and mycelial structures are the primary crystal seeds of hexagonal crystal calcium hydroxide, which can rapidly grow into calcium hydroxide crystals, connect and accumulate on the surface of OS-M(P) to form a large number of layered structures, increasing its surface area. The surface roughness of OS-M(P) increases, the number of pores increases, the surface area increases, and more adsorption sites are exposed, which is conducive to the adsorption of heavy metals.…”

In Situ Ca‐ and Mg‐ Codoped Biochar Derived from Tobacco Stem for Phosphate Adsorption and Desorption

“…Therefore, biochar could better absorb phosphate through static electricity at a low pH. The surface charge of biochar changed gradually with the initial pH increase, which was not conducive to electrostatic adsorption, and a repulsive interaction occurred between phosphate and biochar; the adsorption capacity of biochar for phosphate decreased significantly [50] . At the same time, to assess the effect of pH changes during phosphate adsorption by biochar, it is essential to measure and monitor the pH of the solution throughout the adsorption process Figure 6b.…”

“…The surface charge of biochar changed gradually with the initial pH increase, which was not conducive to electrostatic adsorption, and a repulsive interaction occurred between phosphate and biochar; the adsorption capacity of biochar for phosphate decreased significantly. [50] At the same time, to assess the effect of pH changes during phosphate adsorption by biochar, it is essential to measure and monitor the pH of the solution throughout the adsorption process Figure 6b. The pH of the solution increased significantly when biochar was added to the solution with initial pH 3-7, the pH of the solution increased slightly when biochar was added to the solution with initial pH values 8 and 9, and the pH value of the solution decreased slightly when biochar was added to the solution with initial pH 10 and 11.…”

High Purity Struvite Recovery from Hydrothermally-Treated Sludge Supernatant Using Magnetic Zirconia Adsorbent

“…The differences in the adsorption kinetics were primarily attributed to the competitive effect of the coexisting ions (e.g., sub-Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ ) and organic matter in the HTSS, which inhibited the reaction [ 34 ]. The adsorption kinetics were fitted using the pseudo-first-order and pseudo-second-order models in Equations (7) and (8), respectively [ 35 ]: where C 0 is the initial concentration (mg/L), C t is the concentration at time t (mg/L), and K 1 is the kinetic constant ( ). where t is the contact time (min), q e is the adsorption capacity at adsorption equilibrium (mg/g), q t is the adsorption capacity at time t (mg/g), and K 2 is the kinetic constant (g/(mg∙min)).…”