Mechanistic insights of 2,4-D sorption onto biochar: Influence of feedstock materials and biochar properties

Objective of this study was to investigate the mechanisms of 2,4-Dichlorophynoxy acetic acid (2,4-D) sorption on biochar in aqueous solutions. Sorption isotherm, kinetics, and desorption experiments were performed to identify the role of biochars' feedstock and production conditions on 2,4-D sorption. Biochars were prepared from various green wastes (tea, burcucumber, and hardwood) at two pyrolytic temperatures (400 and 700°C). The tea waste biochar produced at 700°C was further activated with steam under a controlled flow. The sorption of 2,4-D was strongly dependent on the biochar properties such as specific surface area, surface functional groups, and microporosity. The steam activated biochar produced from tea waste showed the highest (58.8mgg -1 ) 2,4-D sorption capacity, which was attributed to the high specific surface area (576m 2 g -1 ). The mechanism of 2,4-D removal from aqueous solution by biochar is mainly attributed to the formation of heterogeneous sorption sites due to the steam activation

Fe(III) loaded chitosan-biochar composite fibers for the removal of phosphate from water

Excess phosphorous (P) in aquatic systems causes adverse environmental impacts including eutrophication. This study fabricated Fe(III) loaded chitosan-biochar composite fibers (FBC-N and FBC-C) from paper mill sludge biochar produced under N2 (BC-N) and CO2 (BC-C) conditions at 600 °C for adsorptive removal of phosphate from water. Investigations using SEM/EDX, XPS, Raman spectroscopy, and specific surface area measurement revealed the morphological and physico-chemical characteristics of the adsorbent. The Freundlich isotherm model well described the phosphate adsorption on BC-N, while the Redlich–Peterson model best fitted the data of three other adsorbents. The maximum adsorption capacities were 9.63, 8.56, 16.43, and 19.24 mg P g−1 for BC-N, BC-C, FBC-N, and FBC-C, respectively, indicating better adsorption by Fe(III) loaded chitosan-biochar composite fibers (FBCs) than pristine biochars. The pseudo-first-order kinetic model suitably explained the phosphate adsorption on BC-C and BC-N, while data of FBC-N and FBC-C followed the pseudo-second-order and Elovich model, respectively. Molecular level observations of the P K-edge XANES spectra confirmed that phosphate associated with iron (Fe) minerals (Fe-P) were the primary species in all the adsorbents. This study suggests that FBCs hold high potential as inexpensive and green adsorbents for remediating phosphate in contaminated water, and encourage resource recovery via bio-based management of hazardous waste