Facile preparation of magnetic porous biochars from tea waste for the removal of tetracycline from aqueous solutions: Effect of pyrolysis temperature

Effective Use of Sugarcane-Bagasse-Derived KOH-Activated Biochar for Remediating Norfloxacin-Contaminated Water

Bagasse-derived biochar (SCB750) was prepared at 750 °C using Chinese sugarcane bagasse as a carbon source and then modified with KOH for the removal of the antibiotic norfloxacin (NOR) from aqueous solutions. 3K-SCB750, prepared using a solid-to-liquid mass ratio of bagasse:KOH = 1:3, was found to have the best adsorption performance for NOR. Under the conditions of pH 5, 25 °C, 2.4 g L-1 adsorbent, and 300 mg L-1 NOR, its adsorption of NOR reached equilibrium (97.5% removal) after 60 min. The adsorption behaviours were in line with the quasi-second-order kinetic and Langmuir isotherm models, respectively. The maximum theoretical adsorption capacity reached up to 157.4 mg·g-1 at 40 °C. The thermodynamic parameters showed that the adsorption of NOR onto 3K-SCB750 was a spontaneous, endothermic, and physical process. In addition, Brunauer-Emmett-Teller analysis (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy were conducted to investigate the structural and adsorption properties of 3K-SCB750. Fourier transform infrared spectroscopy (FTIR) was also applied to understand the mechanism of adsorption of NOR onto 3K-SCB750. All of the results indicated that 3K-SCB750 had a large specific surface area of 1038.8 m2·g-1, an average pore size of 1.9 nm, and hierarchical structures with random pores and cracks for efficient removal of NOR. NOR adsorption mechanisms on 3K-SCB750 were related to the pore-filling effect and electrostatic attraction. Therefore, 3K-SCB750 biochar may be used as a promising adsorbent of antibiotics in wastewaters.

Tetracycline Adsorption Performance and Mechanism Using Calcium Hydroxide-Modified Biochars

Tetracycline is frequently found in various environments and poses significant ecological risks. Calcium hydroxide-modified biochar has shown potential as a material for removing multiple classes of pollutants from wastewater streams. The tetracycline-adsorption performance and mechanism of alkali-modified biochars derived from nine wastes (corn straw, rice straw, swine manure, cypress powder, wheat straw, peanut shell, walnut shell powder, soybean straw, and corncobs) were investigated in the study. Among the four alkalis tested, calcium hydroxide exhibited the most effective modification effects at a pyrolysis temperature of 500 °C. Straw biomass was most suitable to be modified by calcium hydroxide, and calcium hydroxide-modified biochar showed the highest adsorption performance for tetracycline. The maximum adsorption capacities were 8.22 mg g-1 for pristine corn straw biochar and 93.46 mg g-1 for calcium hydroxide-modified corn straw biochar. The tetracycline adsorption mechanism by calcium hydroxide-modified corn straw biochar involved hydrogen bonding, oxygen-containing functional groups, Ca2+ metal complexation, and electrostatic attraction. Consequently, calcium hydroxide-modified corn straw biochar emerges as an environment-friendly, cost-effective, and efficient tetracycline adsorbent.

Preparation of Biochar with Developed Mesoporous Structure from Poplar Leaf Activated by KHCO3 and Its Efficient Adsorption of Oxytetracycline Hydrochloride

The effective removal of oxytetracycline hydrochloride (OTC) from the water environment is of great importance. Adsorption as a simple, stable, and cost-effective technology is regarded as an important method for removing OTC. Herein, a low-cost biochar with a developed mesoporous structure was synthesized via pyrolysis of poplar leaf with potassium bicarbonate (KHCO₃) as the activator. KHCO₃ can endow biochar with abundant mesopores, but excessive KHCO₃ cannot continuously promote the formation of mesoporous structures. In comparison with all of the prepared biochars, PKC-4 (biochar with a poplar leaf to KHCO₃ mass ratio of 5:4) shows the highest adsorption performance for OTC as it has the largest surface area and richest mesoporous structure. The pseudo-second-order kinetic model and the Freundlich equilibrium model are more consistent with the experimental data, which implies that the adsorption process is multi-mechanism and multi-layered. In addition, the maximum adsorption capacities of biochar are slightly affected by pH changes, different metal ions, and different water matrices. Moreover, the biochar can be regenerated by pyrolysis, and its adsorption capacity only decreases by approximately 6% after four cycles. The adsorption of biochar for OTC is mainly controlled by pore filling, though electrostatic interactions, hydrogen bonding, and π-π interaction are also involved. This study realizes biomass waste recycling and highlights the potential of poplar leaf-based biochar for the adsorption of antibiotics.

Trends in removal of pharmaceuticals in contaminated water using waste coffee and tea-based materials with their derivatives

The introduction of large amounts of pharmaceuticals into the environmental waters is well-documented in literature with their occurrence reported in all different water matrices accessible to humans and animals. At the same time, the increasing consumption of coffee and tea-based beverages results in the generation of solid waste, which is mostly disposed-off in the environment. To minimize environmental pollution, coffee and tea-based materials have been proposed as suitable options to remove pharmaceuticals in environmental waters. Therefore, this article provides a critical review on the preparation and applications of coffee and tea-based materials in removing pharmaceuticals from contaminated water. In this context, most studies in literature focused on the applications of these materials as adsorbents, while only limited work on their role in degradation of pharmaceuticals is discussed. The successful application in adsorption studies is attributed to high surface areas of adsorbents and the ability to easily modify the adsorbent surfaces by incorporating functional groups that provide additional oxygen atoms, which promote easy interactions with pharmaceuticals. Hence, the adsorption mechanisms are mostly described by hydrogen bonding, electrostatic and π-π interactions with sample pH playing a dominant role in the adsorption process. Overall, the present article focused on the developments, trends and future research direction on the preparations and applications of coffee and tea-based materials for efficient removal of pharmaceuticals in water. PRACTITIONER POINTS: Review of tea and coffee wastes application for removal of pharmaceuticals in water Key applications in adsorption and degradation of pharmaceuticals in water Removal mostly explained by hydrogen bonding, electrostatic, and π-π interactions Trends, gaps, and future research to be explored are reviewed and highlighted.

Effect of water-washing pretreatment on the enhancement of tetracycline adsorption by biogas residue biochar

Biochar preparation was a feasible strategy for realizing the reduction, harmlessness, and resource utilization of biogas residue (BR) simultaneously. How to enhance the adsorption performance of biogas residue biochar through simple, friendly, and effective way still needs to be investigated. In this study, water-washing pretreatment of BR was adopted before biochar preparation (BRBC-W), and pristine biochar (BRBC) was also produced to serve as control. The adsorption behavior and possible adsorption mechanisms of tetracycline (TC) onto biochars were comprehensively studied. The results showed that water-washing pretreatment could increase the surface area and mesoporous volume of biochar from 358.63 to 391.98 cm³∙g^-1, and 0.459 to 0.488 cm³∙g^-1, respectively. More graphitic structure was observed in BRBC-W. In addition, the surface morphology, element content, minerals composition, and surface functional groups also changed in biochar after water-washing pretreatment. The pseudo-second-order and Redlich-Peterson models better descried the adsorption behavior of TC on BCRBC-W. The maximum adsorption capacity of BRBC and BRBC-W for TC based on Langmuir isotherm was 224.93 and 306.94 mg·g^-1, respectively. The adsorption affinity of BRBC-W toward TC was greater than that of BRBC. BRBC and BRBC-W can effectively remove TC in water within a wide pH range and under the interference of co-existing ions. The adsorption mechanism of TC onto BRBC and BRBC-W included ore filling, π-π interaction, and hydrogen bonding. The enhancement of TC on BRBC-W by water-washing pretreatment was attributable to the strengthening of pore diffusion and π-π interaction. Therefore, water-washing pretreatment effectively enhanced the adsorption performance of BRB, and BRBC-W was an effective eco-friendly adsorbent for the removal of TC from aquatic environment.