Potassium hydroxide-modified algae-based biochar for the removal of sulfamethoxazole: Sorption performance and mechanisms

Hydrothermal N-doping, magnetization and ball milling co-functionalized sludge biochar design and its selective adsorption of trace concentration sulfamethoxazole from waters

This study aimed to design an efficient and easily collected/regenerated adsorbent for trace concentration sulfamethoxazole (SMX) removal to eliminate its negative impacts on human health, reduce the risk of adsorbed SMX release and boost the reusability of adsorbent. Various multiple modified sludge-derived biochars (SBC) were synthesized in this work and applied to adsorb trace level SMX. The results demonstrated that hydrothermal N-doping, magnetization coupled with ball milling co-functionalized SBC (BMNSBC) displayed the greater adsorption ability for SMX. The maximum adsorption capacity of BMNSBC for SMX calculated by Langmuir model was 1.02 × 105 μg/g, which was 12.9 times of SBC. Characterization combined with adsorption experiments (e.g., models fitting) and DFT calculation confirmed that π-π conjugation, Lewis acid-base, pore filling and Fe3O4 complexation were the primary forces driving SMX binding to BMNSBC. These diversified physicochemical forces contributed to the fine anti-interference of BMNSBC to background substances (e.g., inorganic compounds and organic matter) and its remarkable adsorption ability for SMX in diverse real waters. The great magnetization strength of BMNSBC was advantage for its collection and efficient regeneration by NaOH desorption. Additionally, BMNSBC exhibited an outstanding security in view of its low leaching levels of iron (Fe) and total nitrogen (TN). The multiple superiority of BMNSBC enable it to be a prospective material for emerging contaminants (e.g., SMX) purification, also offering a feasible disposal approach for municipal waste (e.g., sludge).

Synthesis, delineation and technological advancements of algae biochar for sustainable remediation of the emerging pollutants from wastewater-a review

The use of algae for value-added product and biorefining applications is enchanting attention among researchers in recent years due to its remarkable photosynthetic ability, adaptability, and capacity to accumulate lipids and carbohydrates. Algae biomass, based on its low manufacturing costs, is relatively renewable, sustainable, environmentally friendly and economical in comparison with other species. High production rate of algae provides a unique opportunity for its conversion to biochar with excellent physicochemical properties, viz. high surface area and pore volume, high adsorption capacity, abundant functional groups over surface, etc. Despite several potential algal-biochar, a detailed study on its application for removal of emerging contaminants from wastewater is limited. Therefore, this technical review is being carried out to evaluate the specific elimination of inorganic and organic pollutants from wastewater, with a view to assessing adsorption performances of biochar obtained from various algae species. Species-specific adsorption of emerging pollutants from wastewater have been discussed in the present review. The promising methods like pyrolysis, gasification, dry and wet torrefaction for the production of algae biochar are highlighted. The strategies include chemical and structural modifications of algae biochar for the removal of toxic contaminants have also been considered in the current work. The overall aim of this review is to confer about the synthesis, technological advancements, delineation and application of algae biochar for the treatment of wastewater.

Effective removal of microplastics by filamentous algae and its magnetic biochar: Performance and mechanism

In recent years, filamentous algae blooms and microplastics (MPs) pollution have become two major ecological and environmental problems in urban water systems. In order to solve these two problems at the same time, this study explored the loading capacity of MPs on fresh filamentous algae, and successfully synthesized magnetic filamentous algae biochar loading with Fe3O4 by hydrothermal method, with the purpose of removing MPs from water. The magnetic filamentous algal biochar was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and so on. Experiments on adsorption kinetics, adsorption isotherms and optimum pH were carried out to explore the adsorption mechanism of MPs on magnetic filamentous algal biochar. The adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was determined by using the residual sum of squares (RSS) and Bayesian information criterion (BIC). Microscope images revealed that fresh filamentous algae could interact with MPs in the form of entanglement, adhesion and encapsulation. The average load of MPs in filamentous algae samples was 14.1 ± 5 items/g dry weight. The theoretical maximum adsorption capacities of polystyrene MPs (PS-MPs) by raw biochar (A500) and magnetic biochar with Fe3O4 (M2A500) were 176.99 mg/g and 215.58 mg/g, respectively. The adsorbent materials gave better reusability because they could be reused up to five times. Overall, these findings have provided new insights into the use of filamentous algae for in situ remediation of fluvial MPs pollution, as well as feasible strategies for the recycling of algal waste.

Research advances on production and application of algal biochar in environmental remediation

Algae, comprising microalgae and macroalgae, have emerged as a promising feedstock for the production of functional biochar. Recently, the application of algal biochar in environmental remediation gains increasing attention. This review summarizes research advancements in the synthesis and application of algal biochar, a versatile and sustainable material for environmental remediation ranging from wastewater treatment to soil improvement. Algal biochar can be prepared by pyrolysis, microwave-assisted pyrolysis, and hydrothermal carbonization. Physical and chemical modifications have proven to be effective for improving biochar properties. Algal biochar is promising for removing diverse pollutants including heavy metals, organic pollutants, and microplastics. The role in soil improvement signifies a sustainable approach to enhancing soil structure, nutrient retention, and microbial activity. Research gaps are identified based on current understanding, necessitating further exploration into variations in biochar characteristics, the performance improvement, large-scale applications, and the long-term evaluation for environmental application. This review provides a better understanding of algal biochar as a sustainable and effective tool in environmental remediation.

Recent progress in TiO2-biochar-based photocatalysts for water contaminants treatment: strategies to improve photocatalytic performance

Toxic organic pollutants in wastewater have seriously damaged human health and ecosystems. Photocatalytic degradation is a potential and efficient tactic for wastewater treatment. Among the entire carbon family, biochar has been developed for the adsorption of pollutants due to its large specific surface area, porous skeleton structure, and abundant surface functional groups. Hence, combining adsorption and photocatalytic decomposition, TiO2-biochar photocatalysts have received considerable attention and have been extensively studied. Owing to biochar's adsorption, more active sites and strong interactions between contaminants and photocatalysts can be achieved. The synergistic effect of biochar and TiO2 nanomaterials substantially improves the photocatalytic capacity for pollutant degradation. TiO2-biochar composites have numerous attractive properties and advantages, culminating in infinite applications. This review discusses the characteristics and preparation techniques of biochar, presents in situ and ex situ synthesis approaches of TiO2-biochar nanocomposites, explains the benefits of TiO2-biochar-based compounds for photocatalytic degradation, and emphasizes the strategies for enhancing the photocatalytic efficiency of TiO2-biochar-based photocatalysts. Finally, the main difficulties and future advancements of TiO2-biochar-based photocatalysis are highlighted. The review gives an exhaustive overview of recent progress in TiO2-biochar-based photocatalysts for organic contaminants removal and is expected to encourage the development of robust TiO2-biochar-based photocatalysts for sewage remediation and other environmentally friendly uses.

Hydrochloric acid-modified fungi-microalgae biochar for adsorption of tetracycline hydrochloride: Performance and mechanism

Novel biochar (BC) was prepared by pyrolysis using Aspergillus oryzae-Microcystis aeruginosa (AOMA) flocs as raw materials. It has been used for tetracycline hydrochloride (TC) adsorption along with acid (HBC) and alkali modification (OHBC). Compared with BC (114.5 m² g^-1) and OHBC (283.9 m² g^-1), HBC had a larger specific surface area (S_BET=338.6 m² g^-1). Meanwhile, the Elovich kinetic and Sip isotherm models adequately fit the adsorption data, and intraparticle diffusion is the controlling factor for TC adsorption diffusion on HBC. Furthermore, the thermodynamic data indicated that this adsorption was endothermic and spontaneous. The experimental results demonstrated that there are multiple interactions during the adsorption reaction process, including pore filling, H-bonds, π-π interaction, hydrophobic affinity, and van der Waals forces. In general, biochar prepared from flocs of AOMA can be used to remediate tetracycline-contaminated water, and it is of great significance in improving resource utilization.

Adsorption of sulfanilamides using biochar derived from Suaeda salsa: adsorption kinetics, isotherm, thermodynamics, and mechanism

Suaeda biochar (SBC) was prepared by muffle furnace with Suaeda salsa at 600, 700, 800, and 900 ℃. The physical and chemical properties of biochar at different pyrolysis temperatures and the adsorption mechanism of sulfanilamide (SM) were studied by SEM-EDS, BET, FTIR, XRD, and XPS analysis. The adsorption kinetics and adsorption isotherms were fitted. The results showed that the kinetics was in line with the quasi-second-order adsorption model and belonged to chemisorption. The adsorption isotherm conformed to Langmuir adsorption isotherm model and belonged to monolayer adsorption. The adsorption of SM on SBC was spontaneous and exothermic. The adsorption mechanism may be pore filling, hydrogen bonding, and π-π electron donor acceptor (EDA) interaction.

A Stable Fe-Zn Modified Sludge-Derived Biochar for Diuron Removal: Kinetics, Isotherms, Mechanism, and Practical Research

To remove typical herbicide diuron effectively, a novel sludge-derived modified biochar (SDMBC600) was prepared using sludge-derived biochar (SDBC600) as raw material and Fe-Zn as an activator and modifier in this study. The physico-chemical properties of SDMBC600 and the adsorption behavior of diuron on the SDMBC600 were studied systematically. The adsorption mechanisms as well as practical applications of SDMBC600 were also investigated and examined. The results showed that the SDMBC600 was chemically loaded with Fe-Zn and SDMBC600 had a larger specific surface area (204 m²/g) and pore volume (0.0985 cm³/g). The adsorption of diuron on SDMBC600 followed pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum diuron adsorption capacity of 17.7 mg/g. The biochar could maintain a good adsorption performance (8.88-12.9 mg/g) under wide water quality conditions, in the pH of 2-10 and with the presence of humic acid and six typical metallic ions of 0-20 mg/L. The adsorption mechanisms of SDMBC600 for diuron were found to include surface complexation, π-π binding, hydrogen bonding, as well as pore filling. Additionally, the SDMBC600 was tested to be very stable with very low Fe and Zn leaching concentration ≤0.203 mg/L in the wide pH range. In addition, the SDMBC600 could maintain a high adsorption capacity (99.6%) after four times of regeneration and therefore, SDMBC600 could have a promising application for diuron removal in water treatment.

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.

Comparison of the performance of hydrochar, raw biomass, and pyrochar as precursors to prepare porous biochar for the efficient sorption of phthalate esters

In this study, three high-performance porous biochars were synthesized by the cocarbonization of Pistia stratiotes-derived precursors (raw biomass, hydrochar and pyrochar) with potassium hydroxide and utilized for the sorption of diethyl phthalate from aqueous solution. The developed pore structure, surface functional groups, high hydrophobicity characteristic and graphene structure of porous biochars contributed to the excellent sorption quantity of up to 813 mg g^-1 (C_e, 25 mg L^-1). Among the three precursors, hydrochar-derived porous biochar showed better properties in terms of its specific surface area and hydrophobicity, and it displayed the highest sorption capacity. The sorption kinetics and isotherm experiments confirmed that pore filling and partitioning dominated the sorption capacity while the mass transfer, hydrogen bonding and π-π stacking in the hydrochar limited the sorption rate. This finding helped to propose a feasible method for the efficient utilization of invasive aquatic plants and provided novel insight into the selection of precursors for preparing porous biochars.

Sustainable synthesis of hydroxyl-functional porous organic framework as novel adsorbent for effective removal of organic micropollutants from water

Organic micropollutants (OMPs) in water resources are a growing threat to aquatic ecosystems and human health. Efficient removal of polar OMPs is very challenging because of their high hydrophility. Synthesizing novel adsorbent capable of high-efficiently removing hydrophilic and hydrophobic micropollutants is highly desirable for water remediation. Here, using natural proanthocyanidin as building units, a novel hydroxyl-functional porous organic framework (denoted as PC-POF) with amphiphilic feature was synthesized through facile azo coupling reaction. Five sulfonamide antibiotics were selected as model OMPs for adsorption study. Adsorption experiments demonstrated a more rapid and efficient sulfonamides capture ability of the PC-POF than that of the most reported adsorbents due to strong hydrogen bonding, π stacking and electrostatic interactions. The PC-POF can be easily recovered and reused at least 5 times without obvious decline in adsorption performance. Moreover, experiments conducted at environmentally relevant concentrations (μg L^-1) further confirmed a notable adsorption performance of the PC-POF even when the sulfonamides solution was rapidly passed through the PC-POF packed column. The PC-POF also showed good adsorption performance for other micropollutants like neonicotinoid insecticides, nitroimidazole antibiotics and triazine herbicides, indicating a promising prospect. This work provides a new strategy to construct amphiphilic adsorbent by using renewable resources for pollutants removal.

Biochar derived carbonaceous material for various environmental applications: Systematic review

Biochar is the solid material produced from the carbonization of organic feedstock biomass. This material has several unique characteristics such as greater carbon content, good electrical conductivity, high stability and large surface area, which can be applied in several research areas such as generation of power and wastewater treatment. In connection with this, recently, the investigations on biochar significantly focus on the removal of toxic heavy metals since the biochar material is easily available and environmentally friendly. According to an environmental analytical device, biochar-derived carbonaceous material has been additionally applied to the synthesis of an effective, sensitive, and low-cost electrochemical sensor. Biochar with an assessment of electrochemical properties has engaged with different redox reactions in water. In this survey, electrochemical ways of behaving of biochar in light of the electrochemical structures were analytically compiled as well as the impact from biomass sources and manufacturing process including carbonization strategies, pre-treatment/changed techniques. This review emphasizes the various synthesis methods of biochar form organic feedstock, properties and different modulations of biochar for the bioremediation of heavy metals. This review study emphasizes the utilization of biochar as sensing platform and supercapacitor for electrode fabrication in electrochemical biosensor to enhance the remediation of toxic contaminants from water streams and by switching the less ecological traditional materials. Brief information on the techniques employed for packaging biochar as carbon electrode is summarized. Scope in the aspect of environmental concern of biochar, future challenges and prospects are proposed in detail.

Progress in microalgal mediated bioremediation systems for the removal of antibiotics and pharmaceuticals from wastewater

Worldwide demand for antibiotics and pharmaceutical products is continuously increasing for the control of disease and improvement of human health. Poor management and partial metabolism of these compounds result in the pollution of aquatic systems, leading to hazardous effects on flora, fauna, and ecosystems. In the past decade, the importance of microalgae in micropollutant removal has been widely reported. Microalgal systems are advantageous as their cultivation does not require additional nutrients: they can recover resources from wastewater and degrade antibiotics and pharmaceutical pollutants simultaneously. Bioadsorption, degradation, and accumulation are the main mechanisms involved in pollutant removal by microalgae. Integration of microalgae-mediated pollutant removal with other technologies, such as biodiesel, biochemical, and bioelectricity production, can make this technology more economical and efficient. This article summarizes the current scenario of antibiotic and pharmaceutical removal from wastewater using microalgae-mediated technologies.

Retention of sulfamethoxazole by cinnamon wood biochar and its efficacy of reducing bioavailability and plant uptake in soil

The objective of this research was to evaluate the efficacy of cinnamon wood biochar (CWBC) in adsorbing sulfamethoxazole (SUL), which alleviates bioavailability and plant uptake. Batch studies at various pH, contact times, and initial SUL loading were used to study SUL adsorption in CWBC, soil, and 2.5% CWBC amended soil. SUL mitigation from plant uptake were examined using Ipomoea aquatica at different SUL contamination levels in the soil. The kinetic results were described by pseudo-second-order with maximum adsorption capacities (Q_max) of 95.64 and 0.234 mg/g for pristine CWBC and amendment, respectively implying that chemical interactions are rate-determining stages. Hill and Toth's model described the isotherm data for pristine CWBC, soil and CWBC amended soil as Q_max of 113.44, 0.72, and 3.45 mg/g. Column data showed a great mobilization of SUL in loamy sand; however, when CWBC was added to the loamy sand, the mobilization was drastically reduced by 98.8%. The Ipomoea aquatica showed a great potential to SUL uptake and it depended on the contamination level; the SUL accumulation in plant was 9.6-13.8 and 19.1-48 mg/kg when soil was spiked with 5 and 50 mg/kg, respectively. The addition of 2.5% CWBC reduced root and shoot uptake by 30 and 95%, respectively in 5 mg/kg of SUL, whereas with 50 mg/kg of SUL, the root and shoot uptake was reduced by 60 and 61%, respectively. The current study suggested CWBC as a possible adsorbent that may be employed to reduce SUL bioavailability in environmental matrices.

Efficient adsorptive removal of fluoroquinolone antibiotics from water by alkali and bimetallic salts co-hydrothermally modified sludge biochar

Fluoroquinolones are one of most commonly used antibiotics for preventing and treating bacterial infections and their unsatisfactory removal by conventional wastewater treatment technology have aroused widespread attention. A novel adsorbent of KMSBC was the first time synthesized and tested to adsorb three typical fluoroquinolone antibiotics of CIP, NOR and OFL from water. The characterization analysis showed that KMSBC possessed the superior porous structure, abundant functional groups and greater graphitic degree. Together with kinetics, isotherms, thermodynamics and critical factors (e.g., biochar dose, reaction time/temperature, fluoroquinolone antibiotics concentration, pH, co-existing ionic strength and HA concentration) analysis suggested that pore filling, π-π conjugation, H-bonding and electrostatic interaction were the key mechanisms for fluoroquinolone antibiotics adsorption by KMSBC. KMSBC exhibited the optimum adsorption performance at pH = 5 despite the adsorbates. The maximum adsorption capacity of KMSBC for CIP, NOR and OFL were 49.9, 55.7 and 47.4 mg/g at 25 °C, respectively. Also, KMSBC exhibited the good magnetic sensitivity and stability with the leaching concentrations of Fe were far below than environmental limit (GB5749-2006) at various pH (from 3 to 12), ionic strength and HA concentrations. Additionally, KMSBC performed a stable sustainable adsorption performance in recycles by NaOH regeneration. Thus, KMSBC had the potential to be a promising adsorbent for fluoroquinolone antibiotics removal with favorable adsorption capacity, environmental security and easy regeneration performance.

Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective

This review gives a proper dedicated understanding of the contamination level, sources, and biological dangers related with different classes of antibiotics in consumable water. The literature on the adsorption of antibiotics is relatively uncommon and developments are still under progression, especially for adsorbents other than activated carbon. Also, adsorption technique has already been applied vastly for water treatment. Notwithstanding significant progressions, designed natural wastewater treatment frameworks are just bearably effective (48-77%) in the expulsion of antibiotics. Hence, the compilation of available literature especially for antibiotic adsorption was much needed. Moreover, the conventional adsorbents have some limitations of their own. In this study, the main focus was laid on unconventional adsorbents such as Biochar, Biopolymers, Carbon Nanotubes, Clays, Metal-Organic Frameworks, Microalgae and some miscellaneous adsorbents. The mechanism of adsorption by the unconventional adsorbents includes electrostatic interactions, π-π bonding, weak Van der Waal forces, H-bonding and surface complexation, which was similar to that of conventional adsorbents and hence these unconventional adsorbents can easily replace the costlier conventional adsorbents with even better adsorption efficiency. This paper also briefly discussed the thermodynamics, adsorption equilibrium; isotherm and kinetics of adsorption. This review paper seizes the critical advances of adsorption phenomenon at various interfaces and lays the foundation for current scenario associated with further progress. Besides, this study would help in understanding the antibiotic adsorption, cost estimation and future goals that will attract the young the researchers of this field.

An efficient, green and sustainable potassium hydroxide activated magnetic corn cob biochar for imidacloprid removal

The extensive use of imidacloprid (IMI) has led to its being frequently detected in natural water, also caused the potential damage to the ecosystem. Development of efficient, green and sustainable technique is demanded to eliminate this problem. A novel biochar (KMCBC) derived from agriculture waste of corn cob was first time co-modified by potassium hydroxide (KOH), ferric chloride (FeCl₃) and zinc chloride (ZnCl₂), which showed the greater adsorption amount (410 mg g^-1 at 298 K) for imidacloprid (IMI). Pseudo-second-order kinetic and Langmuir isotherm models fitted well with the experimental data, together with the physicochemical characterization analysis, demonstrating that the adsorption process of IMI by KMCBC might be mainly controlled by micropore filling, π-π electron donor-acceptor and functional groups interactions (H-bonding and complexation). Additionally, the thermodynamics parameters suggested that IMI adsorption in this study was a spontaneous, endothermic and randomly increasing process. Besides, KMCBC owned the easy separation performance and promising environmental safety, also exhibited a high selective adsorption capacity regardless of solution pH (its optimum adsorption performance for IMI was obtained at pH = 5), inorganic ions strength and humic acid (HA) concentrations. The regenerated KMCBC (synergistic ultrasound/ethanol) could sustainably and efficiently adsorb IMI in the reuse cycles. Therefore, this study provided an efficient, green and sustainable adsorbent of KMCBC for IMI removal.

Biochar based photocatalyst for degradation of organic aqueous waste: A review

The advancement in the treatment technology for wastewater containing recalcitrant pollutants to lower the overall cost and time of the treatment processes is the prime demand. Biochar (BC) based photocatalyst have proved their potential application in the photo-degradation of a wide range of organic pollutants. The structural and chemical properties of the BC enhance the efficacy of photocatalyst, improving its optical properties with increased stability. This review gives an overview of the progress that occurred during the last five years in BC-based photocatalyst for degradation of recalcitrant organic waste in the aqueous system, emphasizing the role of BC in the photocatalytic performance with a brief discussion regarding the various sources of BC and different strategies used to modify the BC. Further, the critical challenges are discussed, which would be confronted during the scaling up and real-time application in wastewater treatment.