Performance of lignin impregnated biochar on tetracycline hydrochloride adsorption: Governing factors and mechanisms

Removal of tetracycline in the water by a kind of S/N co-doped tea residue biochar

Tetracycline (TC) is widely present in the environment, and adsorption technology is a potential remediation method. S/N co-doped tea residue biochar (SNBC) was successfully prepared by hydrothermal carbonization method using tea residue as raw material. S was doped by Na2S2O3·5H2O, and N was doped by N in tea residue. The adsorption efficiency of SNBC could reach 94.16% when the concentration of TC was 100 mg L-1. The adsorption effect of SNBC on TC was 9.38 times more than that of unmodified biochar. Tea biochar had good adsorption effect at pH 4-9. The maximum adsorption capacity of 271 mg g-1 was calculated by the Langmuir isotherm model. The adsorption mechanism involved many mechanisms such as pore filling, π-π interaction and hydrogen bonding. The adsorbent prepared in this study could be used as an effective adsorbent in the treatment of TC wastewater.

Endogenous iron-enriched biochar derived from steel mill wastewater sludge for tetracycline removal: Heavy metals stabilization, adsorption performance and mechanism

Steel mill wastewater sludge, as an iron-enriched solid waste, was expected to be converted into iron-enriched biochar with acceptable environmental risk by pyrolysis. The purpose of our study was to evaluate the chemical speciation transformation of heavy metals in biochar under various pyrolysis temperatures and its reutilization for tetracycline (TC) removal. The experimental data indicated that pyrolysis temperature was a key factor affecting the heavy metals speciation and bioavailability in biochar, and biochar with pyrolysis temperature at 450 °C was the most feasible for reutilization without potential risk. The endogenous iron-enriched biochar (FSB450) showed highly efficient adsorption towards TC, and its maximum adsorption capacity could reach 240.38 mg g-1, which should be attributed to its excellent mesoporous structure, abundant functional groups and endogenous iron cycling. The endogenous iron was converted to a stable iron oxide crystalline phase (Fe3O4 and MgFe2O4) by pyrolysis, which underwent a valence transition to form a coordination complex with TC by electron shuttling in the FSB450 matrix. The study provides a win-win approach for resource utilization of steel wastewater sludge and treatment of antibiotic contamination in wastewater.

Insight into the wheat residues-derived adsorbents for the remediation of organic and inorganic aquatic contaminants: A review

Wheat is a major grain crop of the world that provides a stable food for human consumption. Large amounts of by-products/waste materials are produced after the harvesting and processing of wheat crop. Such materials can cause an environmental issue if not disposed of properly. Several studies have shown that wheat residues can be efficient precursors for adsorbents because of their availability, renewability, lignocellulosic composition, and surface active groups enriched structure. In the literature, there are few review articles that address wheat residues-based adsorbents. However, these reviews were specific in terms of adsorbate or adsorbent and did not provide detailed information about the modification, properties, and regeneration of these adsorbents. This article extensively reviews the utilization of wheat biomass/waste including straw, bran, husk, and stalk as precursors for raw or untreated, chemically treated, carbonaceous, and composite adsorbents against various environmental pollutants. The influences of inlet pollutant amount, adsorbent dose, pH, temperature, and time on the performance of adsorbents against pollutants were considered. The maximum uptakes, equilibrium time, and adsorption nature were identified from isotherms, kinetic, and thermodynamic studies. The highest adsorbed amounts of most tested contaminants were 448.20, 322.58, and 578.13 mg/g for lead, chromium, and copper, 1374.6 and 1449.4 mg/g for methylene blue and malachite green, and 854.75, 179.21, and 107.77 mg/g for tetracycline, phosphate, and nitrate, respectively. For the studied adsorbate/adsorbent systems the adsorption mechanism and regeneration were also discussed. Significant results and future directions are finally presented.

Magnetic biochar enhanced copper immobilization in agricultural lands: Insights from adsorption precipitation and redox

Biochar has exceeded expectations for heavy metal immobilization and has been prepared from widely available sources and inexpensive materials. In this research, coconut shell biochar (CSB), bamboo biochar (BC), magnetic coconut shell charcoal (MCSB), and magnetic bamboo biochar (MBC) were manufactured via co-pyrolysis, and their adsorption properties were tested. The pseudo-secondary (R2 = 0.980-0.985) adsorption kinetic fittings for the four biochas were superior to the pseudo-primary kinetics (R2 = 0.969-0.982). Unmodified biochar adsorption isotherms were more consistent with the Freundlich model, while magnetic biochar fitted Langmuir models better. The maximum adsorption capacity of MCSB for Cu(Ⅱ) reached 371.50 mg g-1. The adsorption mechanisms quantitatively analysis of the biochar indicated that chemical precipitation and ion exchange contributed to the adsorption, in which the magnetic biochar metal-π complexation also enhanced the adsorption. The pot experiment revealed that MCSB (2.0 %DW) significantly enhanced the biomass of lettuce, and facilitated the immobilization of DTPA-Cu (p < 0.05). SEM-EDS, XPS, and FTIR were utilized for morphological characterization and functional group identification, and the increased active adsorption sites (-OH, -COOH, CO, and Fe-O) of MCSB enhanced chemisorption and π-π EDA complexation with Cu(Ⅱ). EEM-PARAFAC and RDA analysis further elucidated that magnetic biochar immobilized copper and reduced biotoxicity (efficiency: 76.12%) by adjusting soil pH, phosphate, and SOM release (negative correlation). The presence of iron oxides (FeOx) promoted in situ adsorption of metallic copper and offered new insights into soil remediation.

Straw-derived biochar for the removal of antibiotics from water: Adsorption and degradation mechanisms, recent advancements and challenges

Antibiotics, a kind of containments with the properties of widely distributed and difficult to degrade, has aroused extensive attention in the world. As a prevalent agricultural waste, straws can be utilized to prepare biochar (straw-derived biochar, SBC) to remove antibiotics from aquatic environment. To date, although a number of review papers have summarized and discussed research on biochar application in wastewater treatment and soil remediation, there are few reviews on SBC for antibiotic removal. Due to the limitations of poor adsorption and degradation performance of the pristine SBC, it is necessary to modify SBC to improve its applications for antibiotics removal. The maximum antibiotic removal capacity of modified SBC could reach 1346.55 mg/g. Moreover, the adsorption mechanisms between modified SBC and antibiotics mainly involve π-π interactions, electrostatic interactions, hydrophobic interactions, and charge dipole interactions. In addition, the modified SBC could completely degrade antibiotics within 6 min by activating oxidants, such as PS, PDS, H2O2, and O3. The mechanisms of antibiotic degradation by SBC activated oxidants mainly include free radicals (including SO4•-, •OH, and O2•-) and non-free radical pathway (such as, 1O2, electrons transfer, and surface-confined reaction). Although SBC and modified SBC have demonstrated excellent performance in removing antibiotics, they still face some challenges in practical applications, such as poor stability, high cost, and difficulties in recycling. Therefore, the further research directions and trends for the development of SBC and biochar-based materials should be taken into consideration.

Removal of tetracycline in aqueous solution by iron-loaded biochar derived from polymeric ferric sulfate and bagasse

In this study, the tetracycline (TC) removal performance of iron-loaded biochar (BPFSB) derived from sugarcane bagasse and polymerized iron sulfate was investigated, and the mechanism of TC removal was also explored by study of isotherms, kinetics and thermodynamics and characterization of fresh and used BPFSB (XRD, FTIR, SEM and XPS). The results showed that under optimized conditions (initial pH 2; BPFSB dosage 0.8 g·L-1; TC initial concentration 100 mg·L-1; Contact time 24 h; temperature 298 K), the removal efficiency of TC was as high as 99.03%. The isothermal removal of TC followed well the Langmuir, Freundlich, and Temkin models, indicating that multilayer surface chemisorption dominated the TC removal. The maximum removal capacity of TC by BPFSB at different temperatures was 185.5 mg·g-1 (298 K), 192.7 mg·g-1 (308 K), and 230.9 mg·g-1 (318 K), respectively. The pseudo-second-kinetic model described the TC removal better, while its rate-controlling step was a combination of liquid film diffusion, intraparticle diffusion, and chemical reaction. Meanwhile, TC removal was also a spontaneous and endothermic process, during which the randomness and disorder between the solid-liquid interface was increased. According to the characterization of BPFSBs before and after TC removal, H-bonding and complexation were the major interactions for TC surface adsorption. Furthermore, BPFSB was efficiently regenerated by NaOH. In summary, BPFSB had the potential for practical application in TC removal.

Hydrothermal Pretreatment of KOH for the Preparation of PAC and Its Adsorption on TC

The environment has been heavily contaminated with tetracycline (TC) due to its excessive use; however, activated carbon possessing well-developed pores can effectively adsorb TC. This study synthesized pinecone-derived activated carbon (PAC) with high specific surface area (1744.659 cm²/g, 1688.427 cm²/g) and high adsorption properties (840.62 mg/g, 827.33 mg/g) via hydrothermal pretreatment methods utilizing pinecones as precursors. The results showed that PAC treated with 6% KOH solution had excellent adsorption properties. It is found that the adsorption process accords with the PSO model, and a large amount of C=C in PAC provides the carrier for π-πEDA interaction. The results of characterization and the isothermal model show that TC plays a key role in the adsorption process of PAC. It is concluded that the adsorption process of TC on PAC prepared by hydrothermal pretreatment is mainly pore filling and π-πEDA interaction, which makes it a promising adsorbent for TC adsorption.

Adsorptive decontamination of antibiotics from livestock wastewater by using alkaline-modified biochar

Efficient abatement of antibiotics from livestock wastewater is in urgent demand, but still challenging. In this study, alkaline-modified biochar with larger surface area (130.520 m² g^-1) and pore volume (0.128 cm³ g^-1) was fabricated and explored for the adsorption of different types of antibiotics from livestock wastewater. Batch adsorption experiments demonstrated that the adsorption process was mainly determined by chemisorption and was heterogeneous, which could be moderately affected by the variations of solution pH (3-10). Furthermore, the computational analysis based on density functional theory (DFT) indicated that the -OH groups on biochar surface could serve as the dominant active sites for antibiotics adsorption due to the strongest adsorption energies between antibiotics and -OH groups. In addition, the antibiotics removal was also evaluated in multi-pollutants system, where biochar performed synergistic adsorption towards Zn²⁺/Cu²⁺ and antibiotics. Overall, these findings not only deepen our understandings on the adsorption mechanism between biochar and antibiotics, but also promote the application of biochar in the remediation of livestock wastewater.

Adsorption of Congo red dye in water by orange peel biochar modified with CTAB

In order to improve the adsorption effect of biochar on Congo red dye, this study used hexadecyl trimethyl ammonium bromide (CTAB) to organically modify orange peel biochar (OBC) to produce CTAB-modified orange peel biochar (NOBC), and the biochar before and after modification was analyzed by SEM-EDS, FTIR and BET. The adsorption performance of NOBC on Congo red dye was investigated and the adsorption mechanism was studied. The results showed that the adsorption amount was influenced by the initial concentration, adsorption time and solution pH. NOBC adsorbed 50 mg L^-1 CR with an equilibrium time of 60 min and an equilibrium amount of 290.1 mg g^-1, while the adsorption equilibrium time of OBC was 210 min and an equilibrium amount of 155.2 mg g^-1, the adsorption of CR by NOBC was above 210 mg g^-1 at pH 2 to 11, NOBC can be recycled three times. The experimental results showed that the adsorption data of CR on NOBC were consistent with the Langmuir isothermal adsorption model and the Pseudo-second-order model, and the mechanism of CR adsorption on NOBC mainly included electrostatic attraction and surface adsorption. In conclusion, NOBC is a promising material for dye wastewater adsorption.

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.