ABSTRACT
Porous biochar containing graphitic carbon materials have received great attention from various disciplines, especially for environmental pollutant treatment, due to their cost-effective and specific textural properties. This study exhibited a two-step strategy to compose lignin-porous biochar containing graphitic carbon (LPGC) from pitch pine sawdust and investigated its adsorptive removal for diclofenac sodium (DCF) from an aqueous solution. Sulfuric acid (H2SO4) was utilized to obtain lignin content from biomass and potassium ferrate (K2FeO4) and was adopted to fulfill the synchronous carbonization and graphitization of LPGC. Through slow pyrolysis in atmospheric N2 (900°C - 2 h), the structure of the as-prepared sample was successfully modified. Using SEM images, a stripped layer structure was observed on the H2SO4-treated sample for both one-step and two-step activated samples, indicating the pronounced effect of H2SO4 in the layering of materials. K2FeO4 acted as an activator and catalyst to convert biomass into the porous graphitic structure. The BET surface area, XRD and Raman spectra analyses demonstrated that LPGC possessed a micro/mesoporous structure with a relatively large surface area (457.4 m2 g-1) as well as the presence of a graphitic structure. Further adsorption experiments revealed that LPGC exhibited a high DCF adsorption capacity (qmax = 159.7 mg g-1 at 298 K, pH = 6.5). The effects of ambient conditions such as contact time, solution pH, temperature, ionic strength, electrolyte background on the uptake of DCF were investigated by a batch adsorption experiment. Results indicated that the experimental data were best fitted with the pseudo second-order model and Langmuir isotherm model. Furthermore, the adsorption of DCF onto the LPGC process was spontaneous and endothermic. Electrostatic interaction, H-bonding interaction, and π-π interaction are the possible adsorption mechanisms. The porous biochar containing graphitic carbon obtained from the lignin content of pitch pine sawdust may be a potential material for eliminating organic pollutants from water bodies.
ABSTRACT
The removal of 17ß-estradiol (E2) from contaminated water on nanoscale Fe-Mn binary oxide-loaded multiwalled carbon nanotubes (MWCNTs/FMBO) was evaluated in this work. The characterizations of the mesoporous adsorbent were analyzed by using SEM, TEM, VSM, XRD, XPS, and FTIR measurements. The effects of experimental conditions in E2 removal, including stabilizer additional level, adsorption time, initial E2 concentration, solution pH, reaction temperature, and foreign ions, were examined. The maximum monolayer adsorption capacity (qm) of MWCNTs/FMBO for E2 in the experiment was 47.25 mg/g as verified by the Langmuir sorption isotherm study. The adsorption process was pH-sensitive with an optimum pH of 7.0. On the kinetics study, the adsorption data could be satisfactorily fitted by the pseudo-second-order kinetics. Thermodynamic parameters indicated that the adsorption process was spontaneous and exothermal. In addition, the foreign ions did not show any noticeable inhibition for E2 removal from the water solution except for PO43- that was adversely affected for E2 uptake than other anions in a certain concentration. The adsorption capacities of the mesoporous adsorbent remained at 86.16% even after five adsorption-desorption cycles without significant loss of capacity, which demonstrated the stability and reusability for further removal of E2. Moreover, both hydrogen bond and π-π interaction might be the dominating adsorption mechanisms for E2 adsorption onto MWCNTs/FMBO.
