Preparation, characterization, and efficient chromium (VI) adsorption of phosphoric acid activated carbon from furfural residue: an industrial waste

Adsorption of crystal violet on activated bamboo fiber powder from water: preparation, characterization, kinetics and isotherms

Biomass-activated carbon has made a great contribution as an adsorbent in the field of dye wastewater treatment. In this study, the response surface method (RSM) based on the Box-Behnken design was used to optimize the preparation process. Bamboo fiber activated carbon (BAC) with a specific surface area of 2892 m² g^-1 and a pore volume of 1.80 cm³ g^-1 was prepared. Various characterization methods (SEM, XPS, XRD, and Raman spectroscopy) were used to analyze the micro-structure of BAC. In the microscopic state, the BAC is fibrous and maintains the originally connected pores of the bamboo fiber. After high-temperature activation, the microcrystallinity of BAC decreases, and the degree of graphitization is low, indicating the presence of amorphous carbon. The adsorption capacity of BAC to crystal violet in simulated wastewater was evaluated via an adsorption experiment. Under the following conditions: the dosage of BAC was 0.04 g, the concentration was 600 mg L^-1, the adsorption temperature and time were 25 °C and 30 min, respectively, and the as-prepared BAC had a 99.96% removal rate. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process of CV on BAC belonged to monomolecular layer adsorption. The adsorption process occurs spontaneously and is accompanied by heat release, and the maximum adsorption capacity of BAC within a given concentration range could reach 1353.09 mg g^-1. SEM-EDS characterization before and after adsorption showed that ion exchange and the presence of oxygen-containing functional groups played an important role in promoting the adsorption process. The results show that BAC considerably affects CV removal, which has great application prospects.

Magnetic biochar based on furfural residue as an excellent candidate for efficient adsorption of Tetracycline, Bisphenol A, Congo red, and Cr6

Magnetic porous adsorbent materials are widely favored for their large specific surface area, good adsorption performance, and ease of separation. This work provided a magnetic biochar derived from furfural residue (M-FRAC) with excellent adsorption properties for various pollutants, including Congo red (CR), Tetracycline (TC), Bisphenol A (BPA), and Cr⁶⁺. The influence of experimental parameters, such as pollutant concentration, contact time, and pH, on the adsorption properties of M-FRAC was studied in detail. The adsorption process was highly dependent on pH and initial contaminant concentration. All pollutant adsorption was favorable under acidic conditions. The optimal pH of the CR, TC, and Cr⁶⁺ adsorption was 5, 4, and 2, respectively, while that of BPA was in the range of 2-5. The experimental equilibrium adsorption amount of CR, TC, BPA, and Cr⁶⁺ by M-FRAC was 110.89, 602.81, 157.76, and 265.31 mg/g, respectively. The adsorption processes of pollutants on M-FRAC were in accordance with the Langmuir isotherm model. The adsorption kinetics fitted the pseudo-second-order (PSO) kinetics model. In addition, M-FRAC could be readily separated from solution by applying an external magnetic field. Therefore, the M-FRAC has a good application prospect in practical industrial wastewater treatment.

Optimized preparation of activated carbon from furfural residue using response surface methodology and its application for bisphenol S adsorption

Furfural residue (FR), a solid waste, was applied as the precursor to prepare activated carbon by steam activation. The Box-Behnken design (BBD) approach-based response surface methodology (RSM) was utilized to optimize the preparation conditions to evaluate their effects on the performance of activated carbon from furfural residue (FRAC). The optimum preparation conditions of FRAC were found as follows: activation temperature of 922 °C, activation time of 62 min, and the mass ratio of char to H₂O of 1:4.5, resulting in 1,501.84 mg/g of iodine adsorption capacity and 1,662.41 m²/g of specific surface area. The FRAC was characterized and then the adsorption performance of bisphenol S (BPS) on FRAC was investigated. Langmuir and Koble-Corrigan isotherm models were well fitted to the experimental data, and the adsorption kinetics process was perfectly described by the pseudo-second-order model. Thermodynamic parameters showed that the adsorption of BPS was a spontaneous exothermic process. Besides, the regeneration efficiency of FRAC was over 97% after five consecutive cycles. The maximum monolayer adsorption capacity of FRAC for BPS was 3.2848 mmol/g at 298 K, indicating that the FRAC was an excellent adsorbent for the removal of BPS from aqueous solutions.