Rapid and efficient adsorption of tetracycline from aqueous solution in a wide pH range by using iron and aminoacetic acid sequentially modified hierarchical porous biochar

A polyfunctionalized carbon framework composite for efficient decontamination of Cr(VI) and polycyclic aromatic nitrides from acidic wastewater

Developing multifunctional engineered adsorbents is an effective strategy for decontaminating the environment from various pollutants. In this study, a polyfunctionalized carbon-framework composite, MSC-CFM, was synthesized. The composite comprises an aromatic carbon framework enriched with various functional groups, including magnetic nanoparticles, hydroxyl, and amino groups. MSC-CFM was used to decontaminate Cr(VI) and polycyclic aromatic nitrides (p-dimethylaminoazobenzene sulfonate (DAS) and diphenyl-4, 4 '-di [sodium (azo-2 -) -1-amino-naphthalene-4-sulfonate] (DANS)) from acidic wastewater. The adsorption capacities of MSC-CFM for Cr(VI), DAS and DANS, quantified using the Langmuir isotherm model, were 161.28, 310.83, and 1566.09 mg/g, respectively. Cr(VI) and PAHs (DAS and DANS) were monolayer adsorbed controlled by chemisorption. MSC-CFM could maintain good adsorption efficiency after up to 6 adsorption and desorption cycles. The presence of polycyclic aromatic nitrides promoted the adsorption of Cr(VI) in the Cr(VI)-DAS/DANS binary systems. Removal of pollutants by MSC-CFM involved a variety of unreported reaction mechanisms, such as electrostatic attraction, redox reaction, anion exchange, intermolecular hydrogen bonding, complexation reaction, π-π interaction, and anion-π interaction. MSC-CFM, enriched with a variety of functional groups, is a promising new material for environmental protection. It has good potential for practical application in treating polluted wastewater.

Preparation of highly adsorptive biochar by sequential iron impregnation under refluxing and pyrolysis at low temperature for removal of tetracycline

Iron-doping modification is a prevailing approach for improving adsorption capability of biochar with environmental friendliness, but usually requires high temperature and suffers from iron aggregation. Herein, a highly adsorptive biochar was manufactured via sequential disperse impregnation of iron by refluxing and pyrolysis at low temperature for eliminating tetracycline (TC) from aqueous solution. Iron oxides and hydroxides were impregnated and stably dispersed on the carbon matrix as pyrolyzed at 200 °C, meanwhile abundant oxygen and nitrogen functional groups were generated on surface. The iron-doped biochar exhibited up to 891.37 mg/g adsorption capacity at pH 5, and could be recycled with high adsorption capability. The adsorption of TC should be mostly contributed to the hydrogen bonding of N/O functional groups and the hydrogen bonding/coordination of iron oxides/hydroxides. This would provide a valuable guide for dispersedly doping iron and conserving functional groups on biochar, and a super iron-doped biochar was prepared with superior recyclability.

Seeking the adsorption of tetracycline in water by Fe-modified sludge biochar at different pyrolysis temperatures

The composite material SBC-Fe-x with sludge and Fe3+ was developed by different calcination temperatures (600, 700, and 800 °C) for the removal of tetracycline (TC). The adsorption rates of SBC-Fe-600, SBC-Fe-700, and SBC-Fe-800 were 77.5%, 89%, and 91%, respectively. Furthermore, the Langmuir model indicated that the maximum adsorption capacity of SBC-Fe-700 (157.93 mg/g) was three times greater than that of SBC-Fe-600. The conclusions were confirmed by a series of characterizations that SBC-Fe-700 showed a larger specific surface area, well-developed pore structure, rich oxygen-containing functional groups and a high degree of graphitization. The results of pH experiments indicated the broad applicability of SBC-Fe-700 for TC adsorption. In addition, SBC-Fe-700 suggested outstanding performance in different water environments. This work produced a feasible adsorbent for the removal of TC, and a new direction for sludge resource utilization was proposed.

Adsorption Characteristics of Ball Milling-Modified Chinese Medicine Residue Biochar Toward Quercetin

Using traditional Chinese medicine residues as raw materials, different biochars (BC) were prepared through oxygen-limited pyrolysis at 300 °C, 500 °C, and 700 °C, and BC was ball-milled to produce ball-milled biochar (BMC). Using these adsorbents to adsorb the allelopathic autotoxic substance quercetin. The physical and chemical properties of various biochars derived from traditional Chinese medicine residues were characterized using the Brunauer-Emmett-Teller-N2 surface areas (BET), scanning electron microscopy (SEM), Fourier transform IR spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy (Raman). The study investigated the effects of the initial pH value, different humic acid concentrations, and multiple adsorption-desorption experiments on the removal of quercetin from the solution. The article discusses the adsorption mechanism of quercetin in solution by biochar from a traditional Chinese medicine residue, based on the results of adsorption kinetics and adsorption isotherm fitting. The findings indicate that increasing the pyrolysis temperature reduces the oxygen-containing functional groups of BC, enhances the aromaticity, and stabilizes the carbon structure. The pore structure of BMC becomes more complex after ball milling, which increases the number of oxygen-containing functional groups on the surface. Among the samples tested, BMC700 exhibits the best adsorption performance, with an adsorption capacity of 293.3 mg·g-1 at 318 K. The adsorption process of quercetin by BMC700 follows the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model. The process is primarily a form of multimolecular layer adsorption. Its mechanism involves the pore-filling effect, hydrogen-bonding interaction, electrostatic interaction, and π-π coexistence, as well as the yoke effect. Additionally, they are highly recyclable and show promise in addressing continuous cropping issues.

One-step synthesis of iron and nitrogen co-doped porous biochar for efficient removal of tetracycline from water: Adsorption performance and fixed-bed column

Here, Fe/N co-doped porous biochars (FeNKBCs) were obtained by grinding corncob, CH3COOK, FeCl3·6H2O, and C3H6N6 via one-step synthesis and were applied to remove antibiotics from wastewater. Notably, CH3COOK had an excellent porous activation ability. The developed nanotubular structure of Fe1N2KBC had a high pore volume (Vtotal) (1.2131 cm3/g) and specific surface areas (SSA) (2083.54 m2/g), which showed outstanding sorption abilities for TC (764.35 mg/g), OTC (560.82 mg/g), SMX (291.45 mg/g), and SMT (354.65 mg/g). The adsorption process of TC was controlled by chemisorption. Moreover, Fe1N2KBC has an excellent dynamic adsorption performance (620.14 mg/g) in a fixed-bed column. The properties of SSA, Vtotal, and the content of graphite N and Fe-N were positively correlated with TC adsorption capacity. The high performance of TC removal was related to π-π stacking, pore-filling, hydrogen bond, and electrostatic interaction. Fe1N2KBC possessed stable sorption amounts in pH 2-12 and actual water, and well reuse performance. The results of this work present an effective preparation method of Fe/N porous biochar for TC-contaminated water remediation.

Fabrication of two novel amino-functionalized and starch-coated CuFe2O4-modified magnetic biochar composites and their application in removing Pb2+ and Cd2+ from wastewater

Novel magnetic biochar composites (SFeCu@SBCO and FeCu@SBCO-NH2) were fabricated by modifying oxidized sawdust biochar (SBCO) with Fe/Cu loading, starch-coating/amination, characterized (FTIR, XRD, BET, SEM-EDS and XPS) and applied in capturing Pb2+ and Cd2+ from wastewater. Adsorption experiments revealed that SFeCu@SBCO and FeCu@SBCO-NH2 exhibited extraordinary adsorption performance toward Pb2+/Cd2+ with the maximum adsorption capacity reaching 184.26/173.35 mg g-1 and 201.43/190.81 mg g-1, respectively, which were >5 times higher than those of SBC. The great increase in adsorption capacity of the two adsorbents was ascribed to the introduction of CuFe2O4 and starch/amino groups. Pb2+ and Cd2+ adsorption was an endothermic reaction controlled by monolayer chemisorption. Complexation and electrostatic attraction were the two predominant mechanisms. Besides, ion exchange together with physical adsorption also occurred during the adsorption. Additionally, the both adsorbents displayed favorable stability and reusability as well as desirable anti-interfering ability to other metal cations. Taken together, the both adsorbents could be utilized as reusable magnetic adsorbents with promising prospect in the effective remediation of Pb2+/Cd2+ contaminated water. The study not only contributed to the better understanding of biochar modification strategy and the application of modified biochar in heavy metals pollutants removal, but also realized resource utilization of biomass waste.

Oxidative magnetization of biochar at relatively low pyrolysis temperature for efficient removal of different types of pollutants

A novel oxidative magnetization, involving phosphomolybdic acid and Fe(NO3)3 co-promoted pyrolysis, was established to manufacture highly adsorptive magnetic biochars for adsorbing aqueous tetracycline, methylene blue, and Cr6+. The modification of phosphomolybdic acid greatly boosted the formation of γ-Fe2O3 and oxygen containing groups with enhancement of specific surface area and pore volume at 400 °C. Importantly, γ-Fe2O3 was stably fixed on surface in quasi-nanoscale. The oxidized magnetic biochar displayed 631.53, 158.45, 155.13 mg/g adsorption capabilities for tetracycline, methylene blue, and Cr6+ with 22.79 emu/g saturation magnetization, respectively. Oxygen containing groups and quasi-nanoscale γ-Fe2O3 served as key adsorption sites for these pollutants. A general oxidative magnetization was established for manufacturing high-performance magnetic biochar through phosphomolybdic acid/Fe(NO3)3 co-promoted pyrolysis at relatively low temperature.

Adsorption properties and mechanism of suaeda biochar and modified materials for tetracycline

Adsorption was an available way to eliminate Tetracycline (TC) from waste water. Suaeda biochar (800SBC) and iron modified biochar (Fe-800SBC) were prepared using pyrolysis under oxygen-limiting conditions. BET and SEM showed that the surface of Fe-800SBC was rougher, and the specific surface area (SBET) was 7 times that of 800SBC. There existed pore filling, ion exchange, metal ion complexation, hydrogen bonds and cation-π interaction mechanism. Both 800SBC and Fe-800SBC conformed to quasi-second-order kinetics model, belonged to chemisorption. Fe-800SBC conformed to Elovich model too. The adsorption process of 800SBC conformed to Freundlich and Sips L-F models, Fe-800SBC conformed to the Sips L-F and Temkin models, identifying the presence of physical and chemical adsorption during adsorption. Response surface method (RSM) was used to optimize important process parameters. The quadratic model was sufficient to predict TC removal response in the range of studied parameters.

One-pot preparation of layered double oxides-engineered biochar for the sustained removal of tetracycline in water

Tetracycline (TC) and sugarcane bagasse had both exerted enormous strain on environmental security. In this work, new composite adsorbent designed by impregnating bio-waste bagasse with magnesium-aluminum layered double oxides (BC-MA) was innovatively brought forward for TC removal. Benefiting from the abundant adsorption sites supplied by developed pores structure (0.308 cm³·g^-1), enlarged surface area (256.8 m²·g^-1) and reinforced functional groups, the maximum adsorption amount of BC-MA for TC reached 250.6 mg g^-1. Moreover, BC-MA displayed desirable adsorption capacity in diverse water environments coupled with excellent sustainable regeneration ability. The absorption process of TC by BC-MA was spontaneous and endothermic, and the pivotal rate-limiting stage pertained to intraparticle diffusion. The mechanisms proposed here mainly concerned π-π interactions, pore filling, complexation and hydrogen bonding. These findings suggested that the synthesis of modified biochar from bagasse would offer new opportunities for simultaneous waste resource reuse and water pollution control.

Effective removal of tetracycline antibiotics from water by magnetic functionalized biochar derived from rice waste

The effective removal of tetracycline antibiotics (TCs) from water is of great significance and remains a big challenge. In this work, a novel magnetized biochar (magnetic functionalized carbon microsphere, MF-CMS) was prepared by the coupling hydrothermal carbonization and pyrolysis activation of starch-rich rice waste using ZnCl₂ and FeCl₃ as activators. As the MF-CMS dose was 2.0 g/L, the initial concentration of TCs was 100 mg/L, the removal rates of tetracycline, doxycycline, oxytetracycline, and chlortetracycline were 96.02%, 96.10%, 96.52%, and 85.88%, respectively. The best modeled on pseudo second order, Langmuir adsorption model, and intraparticle diffusion kinetic models suggested that both chemisorption and physisorption occurred in all removal processes, in which chemisorption dominated. TCs were efficiently adsorbed through the combined effects of pore filling, electrostatic attraction, π-π interactions, and complexation reactions of surface functional groups (such as γ-Fe₂O₃ and FeOOH). The removal rates of TCs after five cycles approximately decreased by 20%. And the cycling and metal ion release experiments of MF-CMS indicated that MF-CMS had good reusability, stability, and safety. The estimated cost of preparing MF-CMS is 5.91 USD per kg, and 1 kg of MF-CMS (consuming 8 kg of waste rice) can approximately treat 0.55 tons of TCs wastewater. Overall, the magnetic biochar derived from starch-rich rice waste as an adsorbent has promising and effective for the removal of TCs from water, but also provides a new idea for the resourceful treatment of solid waste.

Pyrolysis temperature affects the physiochemical characteristics of lanthanum-modified biochar derived from orange peels: Insights into the mechanisms of tetracycline adsorption by spectroscopic analysis and theoretical calculations

Biochar (BC) derived from orange peels was modified using LaCl₃ to enhance its tetracycline (TC) adsorption capacity. SEM-EDS, FT-IR, XRD, and BET were used to characterize the physiochemical characteristics of La-modified biochar (La-BC). Batch experiments were conducted to investigate the effects of several variables like pyrolysis temperature, adsorbent dosage, initial pH, and coexisting ions on the adsorption of TC by La-BC. XPS and density functional theory (DFT) were used to elucidate the TC adsorption mechanism of La-BC. The results demonstrated that La was uniformly coated on the surface of the La-BC. The physiochemical characteristics of La-BC highly depended on pyrolysis temperature. Higher temperature increased the specific surface area and functional groups of La-BC, thus enhancing its TC adsorption capacity. La-BC prepared at 700 °C (BC@La-700) achieved the maximum adsorption capacity of 143.20 mg/g, which was 6.8 and 4.6 times higher than that of BC@La-500 and BC@La-600, respectively. The mechanisms of TC adsorption by La-BC were most accurately described by the pseudo-second-order kinetic model. Furthermore, the adsorption isotherm of La-BC was consistent with the Freundlich model. BC@La-700 achieved good TC adsorption efficiencies even at a wide pH range (pH 4-10). Humic acid significantly inhibited TC adsorption by La-BC. The presence of coexisting ions (NH₄⁺, Ca²⁺, NO₃^-) did not significantly affect the adsorption capacity of La-BC, particularly BC@La-700. Moreover, BC@La-700 also exhibited the best recycling performance, which achieved relative high adsorption capacity even after 5 cycles. The XPS results showed that π-π bonds, oxygen-containing functional groups, and La played a major role in the adsorption of TC on La-BC. The result of DFT showed that the adsorption energy of La-BC was the greatest than that of other functional groups on biochar. Collectively, our findings provide a theoretical basis for the development of La-BC based materials to remove TC from wastewater.

Fe-Al bimetallic oxides functionalized-biochar via ball milling for enhanced adsorption of tetracycline in water

The clusters formed by modified materials on its surface makes the application of functionalized biochars in adsorption face a great challenge. Here, a facile ball milling technology was innovatively proposed to tailor Fe-Al oxides-laden bagasse biochar to fabricate a novel adsorbent (BMFA-BC). Benefited from the increased exposure of Fe-Al oxides and, more importantly, enhanced functional groups by ball milling, the adsorption capacity of BMFA-BC for aqueous tetracycline reached up to 116.6 mg g^-1 at 298 K. And the adsorption performance was temperature-dependent. Characterization analysis, batch sorption (thermodynamics, kinetics, isotherms, chemical factors) as well as data modeling illustrated that this superior adsorption ability could be attributed to π-π conjugation, H-bonding, complexation as well as pore filling. BMFA-BC displayed good adsorption capacity in multiple aqueous environments. The excellent regeneration ability, magnetic susceptibility ensured its viability for sustainable pollutants removal. These superiorities revealed that BMFA-BC was a suitable sorbent for antibiotics elimination.

Ultrahigh sorption of sulfamethoxazole by potassium hydroxide-modified biochars derived from bean-worm skin waste

Food processing of bean worm generates copious amount of skin as solid waste posing a serious environmental concern. The present study utilized bean worm skin (BWS) waste to produce KOH-modified biochars (KBWS-BCs) for the removal of sulfamethoxazole (SMX) from aqueous solution for the first time. Characterization of KBWS-BCs was systematically investigated via multiple instrumental analysis techniques. The sorption performance of KBWS-BCs as a function of solution pH, reaction time, initial SMX concentration, and reaction temperature was investigated using batch experiments. The classic kinetics and isotherm models were employed to fit the sorption data. KBWS-BCs exhibited large surface areas (3331-4742 m² g^-1) and ultrahigh sorption performance for SMX (maximum adsorption capacities of 909-2000 mg g^-1), which were comparable to those of other modified biochars and even those of well-designed materials. Thermodynamic study indicated that the sorption of SMX on KBWS-BCs was a spontaneous (△G° < 0) and exothermic (△H° < 0) process. Mechanism analysis showed that both chemisorption and physisorption were responsible for the adsorption of SMX by KBWS-BCs. Overall, recycling BWS for preparation of high-performance biochars can be a "win-win" strategy for both disposal of BWS and removal of SMX from wastewater.

Recent Advances in Carbon-Based Materials for Adsorptive and Photocatalytic Antibiotic Removal

Antibiotics have been a primary environmental concern due to their widespread dispersion, harmful bioaccumulation, and resistance to mineralization. Unfortunately, typical processes in wastewater treatment plants are insufficient for complete antibiotic removal, and their derivatives in effluent can pose a threat to human health and aquatic communities. Adsorption and photocatalysis are proven to be the most commonly used and promising tertiary treatment methods. Carbon-based materials, especially those based on graphene, carbon nanotube, biochar, and hierarchical porous carbon, have attracted much attention in antibiotic removal as green adsorbents and photocatalysts because of their availability, unique pore structures, and superior physicochemical properties. This review provides an overview of the characteristics of the four most commonly used carbonaceous materials and their applications in antibiotic removal via adsorption and photodegradation, and the preparation of carbonaceous materials and remediation properties regarding target contaminants are clarified. Meanwhile, the fundamental adsorption and photodegradation mechanisms and influencing factors are summarized. Finally, existing problems and future research needs are put forward. This work is expected to inspire subsequent research in carbon-based adsorbent and photocatalyst design, particularly for antibiotics removal.

Removal of ofloxacin from water by natural ilmenite-biochar composite: A study on the synergistic adsorption mechanism of multiple effects

The preparation cost is one of the major constraints for adsorbent applied to practical situations. Here, a novel, economical and eco-friendly ilmenite biochar composite (ILM-BC) was successfully prepared by co-cracking of natural ilmenite and corn stover for the removal ofloxacin from water. The adsorption experiments indicated that the removal ofloxacin by ILM-BC was chemisorption and belonged to a spontaneous and entropy-increasing heat absorption process. Among composites, ILM-BC5 had superior adsorption capacity and stability, with a removal rate 1.6 times higher than that of biochar, and it could remove more than 90% ofloxacin in the pH range of 2-10. Multiple characterization results indicated that the adsorption of ILM-BC was the result of the synergistic effect of pore filling, hydrogen bonding, and π-π interactions. The introduction of ilmenite promoted hydrogen bonding formation and π-π interactions by enriching -OH and -COO on the surface of ILM-BC, which could enhance the adsorption capacity of ILM-BC.

Co-doped Fe-MIL-100 as an adsorbent for tetracycline removal from aqueous solution

In the study, Fe-MIL-100 was modified by adding Co²⁺ in the synthesis process; Co/Fe-MIL-100 was successfully synthesized and used to adsorb tetracycline. The addition of Co²⁺ increased the thermal stability of Fe-MIL-100 without changing the crystal structure. It was found that Co/Fe-MIL-100 exhibited satisfactory performance in tetracycline removal, the tetracycline removal efficiency reached almost 100% in the initial concentration range of 10-40 mg/L, and it still reached 82.38% under the condition of 60 mg/L tetracycline. Besides, the factors of tetracycline concentration, pH and inorganic anion on removal efficiency were explored. The coexistence of inorganic anion decreased the adsorption capacity of tetracycline due to the competitive adsorption. CO₃^2- had a more obvious inhibition effect on the adsorption efficiency of tetracycline than Cl^-. The fitting correlation coefficient of Langmuir model was higher and the kinetics better fitted by pseudo-second-order, respectively. As a result of its high removal efficiency and excellent recycling performance, it has great potential in application fields such as removing tetracycline from wastewater.