Oxidized biochar obtained from pine needles as a novel adsorbent to remove caffeine from aqueous solutions

Revolutionizing wastewater treatment: A review on the role of advanced functional bio-based hydrogels

Water contamination poses a significant challenge to environmental and public health, necessitating sustainable wastewater treatment solutions. Adsorption is one of the most widely used techniques for purifying water, as it effectively removes contaminants by transferring them from the liquid phase to a solid surface. Bio-based hydrogel adsorbents are gaining popularity in wastewater treatment due to their versatility in fabrication and modification methods, which include blending, grafting, and crosslinking. Owning to their unique structure and large surface area, modified hydrogels containing reactive groups like amino, hydroxyl, and carboxyl, or functionalized hydrogels with inorganic nanoparticles particularly graphene nanomaterials, have demonstrated promising adsorption capabilities for both inorganic and organic contaminants. Bio-based hydrogels have excellent physicochemical properties and are non-toxic, environmentally friendly, and biodegradable, making them extremely effective at removing contaminants like heavy metal ions, dyes, pharmaceutical pollutants, and organic micropollutants. The versatility of hydrogels allows for various forms to be used, such as films, beads, and nanocomposites, providing flexibility in handling different contaminants like dyes, radionuclides, and heavy metals. Additionally, researchers also have shown the potential for recycling and regenerating post-treatment hydrogels. This approach not only addresses the challenges of wastewater treatment but also offers sustainable and effective solutions for mitigating water pollution.

Efficient Decaffeination with Recyclable Magnetic Microporous Carbon from Renewable Sources: Kinetics and Isotherm Analysis

Rapid global urbanization and population growth have ignited an alarming surge in emerging contaminants in water bodies, posing health risks, even at trace concentrations. To address this challenge, novel water treatment and reuse technologies are required as current treatment systems are associated with high costs and energy requirements. These drawbacks provide additional incentives for the application of cost-effective and sustainable biomass-derived activated carbon, which possesses high surface area and low toxicity. Herein, we synthesized microporous activated carbon (MAC) and its magnetic derivative (m-MAC) from tannic acid to decaffeinate contaminated aqueous solutions. Detailed characterization using SEM, BET, and PXRD revealed a very high surface area (>1800 m2/g) and a highly porous, amorphous, heterogeneous sponge-like structure. Physicochemical and thermal analyses using XPS, TGA, and EDS confirmed thermal stability, unique surface moieties, and homogeneous elemental distribution. High absorption performance (>96 %) and adsorption capacity (287 and 394 mg/g) were recorded for m-MAC and MAC, respectively. Mechanistic studies showed that the sorption of caffeine is in tandem with multilayer and chemisorptive mechanisms, considering the models' correlation and error coefficients. π-π stacking and hydrogen bonding were among the interactions that could facilitate MAC-Caffeine and m-MAC-Caffeine bonding interactions. Regeneration and reusability experiments revealed adsorption efficiency ranging from 90.5-98.4 % for MAC and 88.6-93.7 % for m-MAC for five cycles. Our findings suggest that MAC and its magnetic derivative are effective for caffeine removal, and potentially other organic contaminants with the possibility of developing commercially viable and cost-effective water polishing tools.

Characterization and Performance of Peanut Shells in Caffeine and Triclosan Removal in Batch and Fixed-Bed Column Tests

Peanut shells' adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The parameters examined included peanut shell particle size (120-150, 300-600, and 800-2000 µm), adsorbent dose (0.02-60 g/L), contact time (up to 180 min), bed height (4-8 cm), and hydraulic loading rate (2.0 and 4.0 m3/m2-day). After determining the optimal adsorption conditions, kinetics, isotherm, and breakthrough curve models were applied to analyze the experimental data. Peanut shells showed an irregular surface and consisted mainly of polysaccharides (around 70% lignin, cellulose, and hemicellulose), with a specific surface area of 1.7 m2/g and a pore volume of 0.005 cm3/g. The highest removal efficiencies for caffeine (85.6 ± 1.4%) and triclosan (89.3 ± 1.5%) were achieved using the smallest particles and 10.0 and 0.1 g/L doses over 180 and 45 min, respectively. Triclosan showed easier removal compared to caffeine due to its higher lipophilic character. The pseudo-second-order kinetics model provided the best fit with the experimental data, suggesting a chemisorption process between caffeine/triclosan and the adsorbent. Equilibrium data were well-described by the Sips model, with maximum adsorption capacities of 3.3 mg/g and 289.3 mg/g for caffeine and triclosan, respectively. In fixed-bed column adsorption tests, particle size significantly influenced efficiency and hydraulic behavior, with 120-150 µm particles exhibiting the highest adsorption capacity for caffeine (0.72 mg/g) and triclosan (143.44 mg/g), albeit with clogging issues. The experimental data also showed good agreement with the Bohart-Adams, Thomas, and Yoon-Nelson models. Therefore, the findings of this study highlight not only the effective capability of peanut shells to remove caffeine and triclosan but also their versatility as a promising option for water treatment and sanitation applications in different contexts.

Evaluation of hydrochar from peach stones for caffeine removal from aqueous medium and treatment of a synthetic mixture

The presence of micropollutants, such as caffeine (CAF), has been detected throughout the world, since conventional treatment plants are not able to properly degrade them. CAF is a widely consumed stimulant, and has been demanding the development of efficient methodologies for its removal. Aiming at the agriculture waste valorization, a new hydrochar was developed based on chemical and thermal modification of peach stones (mod-PS) for CAF removal from water and from a synthetic mixture. The morphology, functional groups and surface electrical charge of the adsorbent were characterized by SEM, FTIR and zeta potential, respectively. Regarding CAF adsorption performance, the equilibrium time was reached at 480 min and the pseudo-second-order model presented the best fit for the experimental data. The maximum adsorption capacity was 68.39 mg g-1 (298 K) and the Langmuir model exhibited a better fit for the isothermal data. The thermodynamic properties confirmed that the process was exothermic, spontaneous and reversible. The main adsorption mechanisms were hydrogen bonds and π-interactions. The global removal efficiency was satisfactory in the synthetic mixture simulating real wastewater (67%). Therefore, the proposed new hydrochar has potential application as a low-cost adsorbent for CAF removal.

A critical review on biochar production from pine wastes, upgradation techniques, environmental sustainability, and challenges

Pine wastes, including pine needles, cones, and wood, are abundantly produced as an agroforestry by-product globally and have shown tremendous potential for biochar production. Various thermochemical conversion technologies have exhibited promising results in converting pine wastes to biochar, displaying impressive performance. Hence, this review paper aims to investigate the possibilities and recent technological advancements for synthesizing biochar from pine waste. Furthermore, it explores techniques for enhancing the properties of biochar and its integrated applications in various fields, such as soil and water remediation, carbon sequestration, battery capacitor synthesis, and bio-coal production. Finally, the paper sheds light on the limitations of current strategies, emphasizing the need for further research and study to address the challenges in pine waste-based biochar synthesis. By promoting sustainable and effective utilization of pine wastes, this review contributes to environmental conservation and resource management.

Theoretical verification on adsorptive removal of caffeine by carbon and nitrogen-based surfaces: Role of charge transfer, π electron occupancy, and temperature

Eliminating an emerging water pollutant, caffeine molecules, from an aqueous solution using carbon and nitrogen-based adsorbents is of significant interest to public health. These adsorbents have been shown to have decent adsorption capacity toward caffeine due to their surface functionality. Therefore, screening various carbon and nitrogen-based surfaces can be a better option for high-performance adsorbents to remove caffeine efficiently from wastewater. Herein, we present combined first principles and molecular dynamics quantification of the adsorption enthalpies of caffeine molecules on the possible active sites of carbon and nitrogen-based adsorbents (graphene, phagraphene, graphdiyne, single-wall carbon nanotube, fullerene, and graphitic carbon nitride) with the incorporation of Van der Waals interactions. From the DFT calculations, N-doped carbon surfaces show the highest adsorption energies of single and dimer CAF compared to pristine carbon-based adsorbents. A charge density difference and Bader charge analysis display that high charge transfer occurs between the caffeine's oxygen and the surface's nitrogen atoms. An abundance of π-electrons from the nitrogen atoms, composed of large electron clouds of aromatic rings on the graphitic carbon surface, tends to favor extensive π-π interactions with the caffeine molecule. The high value of pz electron occupancy (1.445) of N in the hexagonal ring of the graphitic surface transfers additional charge transfer, which leads to strong adsorption energy of CAF than pristine surfaces. Also, the g-C3N4 surface adsorbs the CAF molecule with higher adsorption than other N-doped carbon surfaces due to the high pz_eo (1.5448) of N atoms on the surface. At 310 K, the water molecules' kinetics aids the single and dimer caffeine molecules to adsorb with the highest adsorption energies on the active sites of g-C3N4 surfaces than graphene adsorbent.

Performance of hybrid biofilter based on rice husks/sawdust treating grey wastewater

An innovative nature-based technology for wastewater treatment is the hybrid biofiltration, which combines complex symbiotic relationships between plants, earthworms and microorganisms with adequate support components. This latter could be optimized using organic supports. The aim of this research was to evaluate the performance of hybrid biofilters based on rice husks/sawdust treating grey wastewater from mining camps. Four biofilters using an active layer (rice husks/sawdust: 50/50%, v/v) at 60(B₆₀) and 45(B₄₅) cm height and operating for 64 days at a hydraulic loading rate between 1 and 5 m³/m²d were monitored. Eisenia foetida Savigny and Cyperus papyrus L. were used as a biotic component. COD, N-NH₄⁺, NO₃^-, NO₂^-, PO₄^3- and fecal coliforms were weekly monitored. Results showed that the most efficient HB was using 60 cm as an active layer and operating at 3 m³/m²d, which reported average removal efficiencies for COD, NH₄⁺, NO₃^-, PO₄^3- and fecal coliforms up to 85, 89, 47, 49 and 99.9%, respectively. Organic support improved the rate growth for Cyperus papirus L. and E. foetida Savigny up to 50%. Hybrid biofiltration using organic residues is low-cost, providing all-encompassing operational and performance features, improving the wastewater reclamation opportunities.

Cellulosic pine needles-based biorefinery for a circular bioeconomy

Pine needles (PNs) are one of the largest bio-polymer produced worldwide. Its waste, i.e., fallen PNs, is mostly responsible for forest fires and is a major challenge. In present article, we have reviewed differenteffortsmadeto tackle this situation. PNs have been used in various fields such asin composite, water purification industries,electronic devices, etc. Gasification is one of the appealing processes for turning PNs into bio-energy; pyrolysis technique has been employed to create various carbon-based water purification materials; saccharification combined with fermentation produced good yields of bio-ethanol; Pd or Ni/PNs biocatalyst showed good catalytic properties in variousreactionsand pyrolysis with or without catalyst is an alluring technique to prepare bio-fuel. Nano cellulose extracted from PNs showed appealing thermal and mechanical strength. The air quality of nearbyenvironment was examinedby studying the magnetic properties of PNs. Packing materials made of PNs showed exceptional ethylene scavenging abilities.

Biochar-mediated removal of pharmaceutical compounds from aqueous matrices via adsorption

Pharmaceutical is one of the noteworthy classes of emerging contaminants. These biologically active compounds pose a range of deleterious impacts on human health and the environment. This is attributed to their refractory behavior, poor biodegradability, and pseudopersistent nature. Their large-scale production by pharmaceutical industries and subsequent widespread utilization in hospitals, community health centers, and veterinary facilities, among others, have significantly increased the occurrence of pharmaceutical residues in various environmental compartments. Several technologies are currently being evaluated to eliminate pharmaceutical compounds (PCs) from aqueous environments. Among them, adsorption appears as the most viable treatment option because of its operational simplicity and low cost. Intensive research and development efforts are, therefore, currently underway to develop inexpensive adsorbents for the effective abatement of PCs. Although numerous adsorbents have been investigated for the removal of PCs in recent years, biochar-based adsorbents have garnered tremendous scientific attention to eliminate PCs from aqueous matrices because of their decent specific surface area, tunable surface chemistry, scalable production, and environmentally benign nature. This review, therefore, attempts to provide an overview of the latest progress in the application of biochar for the removal of PCs from wastewater. Additionally, the fundamental knowledge gaps in the domain knowledge are identified and novel strategic research guidelines are laid out to make further advances in this promising approach towards sustainable development.

Adsorption of caffeine using steel wastes

Caffeine is the most widespread active pharmaceutical compound in the world, generally studied as a tracer of human pollution, since caffeine levels in surface water correlate with the anthropogenic load of domestic wastewater. This work investigated the use of different steel wastes named as SW-I, SW-II, SW-II, SW-IV, SW-V, and SW-VI in the adsorption of caffeine. These materials were pretreated and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and point of zero charge. The samples are mainly composed of iron (hematite and magnetite). The caffeine adsorption test indicated that SW-VI (steel slag dust) is the most efficient and promising (removal around 51.68%) in relation to the other residues, which it was selected for further studies. Equilibrium time was reached within 96 h of contact between the adsorbent and the adsorbate, with removal of 84.00%, 81.09%, and 73.19% for the initial concentrations of 10 mg L-1, 20 mg L-1, and 30 mg L-1 of caffeine. The pseudo-first-order, pseudo-second-order, and Elovich models presented a good fit to the experimental data. However, the pseudo-first order model described better the experimental behavior. Adsorption isotherms were performed at three temperatures (298, 308, and 318 K). The maximum adsorption capacity was 17.46 ± 2.27 mg g-1, and experimental data were better fitted by the Sips isotherm. Values of ΔG° and parameters equilibrium of the models of Langmuir, Sips, and Temkin were calculated from the standard enthalpies and standard entropies estimated. The values of ΔG° were negative for the temperatures studied indicating that the adsorption process is viable and spontaneous. Negative values for ΔH° were also found, indicating that the process of caffeine adsorption by SW-VI is an exothermic process (0 to -40 kJ mol-1). Thus, the adsorption of caffeine by SW-VI is a physical process. The SW-VI material showed economic viability and promising for the adsorption of caffeine in aqueous media.

Mechanism and behavior of caffeine sorption: affecting factors

Caffeine is one of the emerging pollutants with a diverse chemical composition. It is mixed with the hydrobiota as a result of its high consumption, and when certain dose intervals are exceeded, it re-enters the human body through indirect routes such as plants, animals, soil, water, and the food chain, causing health problems that are difficult or impossible to treat, and irreversible environmental problems. This situation raises concerns about the presence of pollutants emerging in water resources, igniting interest in water treatment processes and the development of alternative methods. Although there are several methods for removing caffeine from aqueous media, adsorption is the most popular because it is less expensive than other methods and has the highest removal efficiency. Furthermore, it has the benefit of selectively attaching the molecules in solution. In this article, studies on the caffeine adsorption process have been examined, and the caffeine adsorption efficiency of various adsorbents has been summarized by compiling information such as pH, contact time, temperature, and concentration of adsorbent and adsorbate, which are considered as optimum processing conditions. The binding mechanism was investigated, and it was clearly stated how caffeine adheres to the adsorbent surface. Among the equilibrium adsorption isotherms, the isotherm model with the best agreement with the experimental data was attempted to be determined. Many studies clearly show that the process of developing environmentally friendly and high-capacity adsorbents in sustainable processes and in harmony with the circular economy is increasing day by day.

Highly effective adsorption of caffeine by a novel activated carbon prepared from coconut leaf

The disposal of coconut wastes is costly and damaging to the environment, but its uses are advantageous activated carbons production. Coconut leaves waste were used for activated carbon production by pyrolysis at 500° C and activation with potassium carbonate. The activated carbon was used for caffeine removal from aqueous solution. The coconut leaves activated carbon showed a predominantly amorphous structure from X-ray diffraction analysis and a pH at the zero charge point of 7.9. From the N₂ adsorption/desorption method, the adsorbent showed a predominance of mesopores, with average pore size of 45.48 ηm and a surface area of 678.03 m²/g. From kinetic studies the data followed the pseudo-second order, where the intraparticle diffusion can be neglected. The adsorption isotherms were satisfactorily adjusted for the Redlich-Peterson model and a type curve L was identified. The thermodynamic parameters showed that adsorption occurred spontaneously, was exothermic and governed by physical adsorption. The artificial neural networks developed were capable of predicting both kinetics and equilibrium adsorption data under different operating conditions and was comparable to the traditional models available in literature in the training experiments, encouraging its use for data generalization when an efficient dataset is used. In conclusion, coconut leaves waste showed to be a promising feedstock to produce activated carbon aiming caffeine removal from water and wastewater.

Bioremoval of toxic malachite green from water through simultaneous decolorization and degradation using laccase immobilized biochar

In this study, decolorization and degradation of malachite green dye was studied using the laccase immobilized pine needle biochar. Successful immobilization of biochar was achieved by adsorption and confirmed through scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX), Fourier transform infrared spectroscopy (FTIR). High laccase binding of 64.4 U/g and high immobilization yield of 78.1% was achieved using 4U of enzyme at pH3 and temperature 30 °C. The immobilized laccase retained >50% relative activity in the pH range 2-7, >45% relative activity at 65 °C and >55% relative activity at 4 °C for 4 weeks. The re-usability of immobilized enzyme was checked with 2, 2'-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) substrate and enzyme retained 53% of its activity after 6 cycles. Immobilized laccase was used for the degradation and decolorization of azo dye malachite green in aqueous solution. More than 85% removal of malachite green dye (50 mg/L) was observed within 5 h. FTIR and high performance liquid chromatography (HPLC) analysis clearly indicated the breakdown of dye and presence of metabolites (leuco malachite green, methanone, [4-(dimethyl amino)pheny]phenyl and 3-dimethyl-phenyl amine) in gas chromatography-mass spectrometry (GC-MS) analysis confirmed the dye degradation. Phytotoxicity analysis indicated that the enzymatic degradation resulted in lesser toxic metabolites than the original dye. Thus, laccase immobilized biochar can be used as an efficient biocatalytic agent to remove dye from water.

Removing Pollutants from Sewage Waters with Ground Apricot Kernel Shell Material

For the first time, a comprehensive review of the literature data on the use of apricot (Prunus armeniaca) biomass components as a sorption material for the treatment of wastewater and environmental water from various pollutants is carried out in the present study. In addition to a comprehensive analysis of contemporary studies, the current work carried out its own microstructural and energy dispersive studies. It shows that apricot kernel shell is a promising raw material for obtaining sorption materials that can be used to extract various pollutants from aqueous media. The parameters of sorption interaction are presented, at which the highest rate of removal of pollutants was achieved. It is shown that the sorption capacity of apricot biomass components can be increased by modifying it with various chemical reagents, as well as other physical and physicochemical methods. We reveal that most publications consider the use of the latter as a raw material for the production of activated carbons. It is established that the surface area and total pore space of activated carbons from apricot kernel shells depend on the modes of carbonization and activation. It is shown that activated carbons are effective adsorbents for removing various pollutants (metal ions, dyes, oil and oil products) from aqueous media. It was found that the adsorption isotherms of pollutants in most cases are best described by the Langmuir and Freundlich models, and the process kinetics is most often described by the pseudo-second-order model. The possibility of improving the sorption characteristics of apricot biomass during chemical or physicochemical treatment is also shown.

Caffeine adsorptive performance and compatibility characteristics (Eisenia foetida Savigny) of agro-industrial residues potentially suitable for vermifilter beds

The caffeine adsorptive performance and compatibility characteristics (Eisenia foetida Savigny) of rice husk, peanut shell, corn cob and coconut fiber were studied, aiming to assess the suitability of these residues for vermifilter beds. For this purpose, the agro-industrial residues were characterized and the E. foetida Savigny compatibility was determined by acute and chronic toxicity tests. Batch adsorption tests were performed using caffeine solutions. Optimal adsorption conditions, kinetic models, isotherm type and the influence of three particle sizes (120-150, 300-600, 800-2000 μm) in the caffeine removal were determined. Coconut fiber (120-150 μm) proved to be the most efficient residue for the caffeine removal (94.2%), requiring 4 g/L for 30 min. However, coconut fiber was the less compatible for earthworms (14d-LC₅₀ = 82%). The results obtained allow to define adequate strategies, such as mixing highly adsorptive residues with the more compatible ones, to choose the most effective materials for vermifiltration technologies.

A Review of Caffeine Adsorption Studies onto Various Types of Adsorbents

A systematic literature review of publications from 2000 to 2020 was carried out to identify research trends on adsorbent materials for the removal of caffeine from aqueous solutions. Publications were retrieved from three databases (Scopus, Web of Science, and Google Scholar). Words "adsorption AND caffeine" were examined into titles, abstracts, and keywords. A brief bibliometric analysis was performed with emphasis on the type of publication and of most cited articles. Materials for the removal of caffeine were classified according to the type of material into three main groups: organic, inorganic, and composites, each of them subdivided into different subgroups consistent with their origin or production. Tables resume for each subgroup of adsorbents the key information: specific surface area, dose, pH, maximum adsorption capacity, and isotherm models for the removal of caffeine. The highest adsorption capacities were achieved by organic adsorbents, specifically those with granular activated carbon (1961.3 mg/g) and grape stalk activated carbon (916.7 mg/g). Phenyl-phosphate-based porous organic polymer (301 mg/g), natural sandy loam sediment (221.2 mg/g), composites of MCM-48 encapsulated graphene oxide (153.8 mg/g), and organically modified clay (143.7 mg/g) showed adsorption capacities lower than those of activated carbons. In some activated carbons, a relation between the specific surface area (SSA) and the maximum adsorption capacity (Q max) was found.

Caffeine removal from aqueous media by adsorption: An overview of adsorbents evolution and the kinetic, equilibrium and thermodynamic studies

Caffeine is an emerging pollutant and is considered the most representative pollutant of the Pharmaceutical Active due to its high consumption by the general population. It can be used to track pollution caused by humans. Different technologies have been employed to remove the caffeine from aqueous media, however the adsorption has been preferred due to its simplicity, high removal efficiency, operational and implementation facility and low cost. This paper provides a systematic review of the published peer-reviewed literature concerned with caffeine removal by the adsorption process. The Scopus and ScienceDirect databases were used to identify relevant articles researches on caffeine removal. Many authors have studied caffeine's adsorption equilibrium in aqueous media, different conditions, and different adsorbents. This paper aims to uncover the overall trend of adsorbent used, kinetic and thermodynamic studies. The impact of pH, temperature, adsorbent dosage and competitive effect were presented and analyzed. It was observed that the adsorption capacities ranged between 10 and 1000 mg g^-1, according to the nature and properties of the adsorbent. The pseudo-second order (kinetic model) and the Langmuir isotherm model showed the best adjustment of the experimental data from caffeine adsorption in most studies. The mechanistic understanding of adsorption and the development of new adsorbents are still a matter of future research, as well as the use of other kinetic models based on statistical factors and the thermodynamic studies should be considered.

Immobilization and retention of caffeine in soil amended with Ulva reticulata biochar

The goal of the present study was to evaluate the immobilization and retention of caffeine (CFN) in soil and the influence of biochar for the CFN transport in agricultural soil. The biochar was produced from the Ulva reticulata seaweed biomass (ULBC) under the slow-pyrolysis with a heating rate of 7 °C/min at 500 °C and characterized using XRD and FTIR. The CFN retention and transport abilities in loamy sand and ULBC amended (2.5%) soil were evaluated under various pH values range of 3-10 and at various CFN concentrations using batch and column experiments. The surface orientation of ULBC was portrayed as the randomized distribution of hetero and homogeneous nature. The highest retention capacity (40 μg/g) was obtained at pH 4.0. Soil amendment with ULBC shows a higher retention affinity towards CFN, of up to 150 μg/g than soil, with minimal pH dependence. The maximum CFN adsorption capacities of soil and amended soils were 420 and 820 μg/g, respectively, based on the Langmuir model. Batch experiments suggested the adsorption of CFN by the biochar amended loamy soil is governed by the electrostatic attraction. The column experiment data demonstrated a high transport potential of CFN in the loamy sand; however, a strong cumulative reduction of transport (58%) was observed with the application of ULBC into the loamy sand. Thus, the addition of seaweed biochar as an amendment in soils with biosolids and wastewater irrigation may reduce the mobilization of CFN to the aquatic system and possibly reduce plant uptake.

Caffeine removal by Gliricidia sepium biochar: Influence of pyrolysis temperature and physicochemical properties

The present study aimed to envisage the effect of physicochemical properties on the performance of Gliricidia sepium biochar (GBC) pyrolyzed at 300, 500, and 700 °C in the removal caffeine (CFN); a pharmaceutical and personal care product, from water. The physicochemical properties of GBC were characterized by proximate and ultimate analysis, BET, SEM, FTIR, and Raman spectroscopy. The adsorption batch experiment was carried out at various pH values (pH 3-10), mixing times (up to 24 h), and initial CFN concentration (10-500 mg/L). The FTIR analysis revealed the loss of polar functional groups on the surface of GBC derived at high temperatures. The red-shifted and blue-shifted Raman peaks indicate the condensation of small molecules on GBC. The GBC derived at 700 °C demonstrated high CFN adsorption capacity (16.26 mg/g) due to its high surface area and aromaticity. The highest adsorption of CFN was occurred at acidic pH range from 3.5 to 4.5 due to the existence of non-specific attraction between CFN and GBC. The kinetics and isotherm experimental data were fitted with Elovich and fractional power kinetic regression, Freundlich, and Temkin isotherm models, which suggested the adsorption of CFN on the GBC by mixed mechanisms; physisorption and chemisorption including π-π interactions, hydrogen bonding, n-π interactions, electrostatic attraction, and electron donor-acceptor attraction. Moreover, both surface area and aromaticity index have demonstrated a high positive correlation for CFN adsorption, signifying the importance of controlling physicochemical properties based on the end-user purpose of biochar.

Caffeine removal using Elaeis guineensis activated carbon: adsorption and RSM studies

The palm (Elaeis guineensis), known as dendê, is an important oleaginous Brazilian plant with a high performance of oil production. In this work, a 2³ full experimental design was performed and the response surface method (RSM) was used to indicate the optimum parameter of caffeine adsorption on Elaeis guineensis endocarp activated carbon, since the endocarp is the main by-product from dendê oil production. It was set the adsorbent point of zero charge (pH_pzc), and the material was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The RSM results indicate removal efficiency (%) at the optimal conditions, 0.20 g of adsorbent, and caffeine initial concentration of 20 mg/L, and acidic medium was about 95%. Based on ANOVA and F test (F_calculated > F_standard), the mathematical/statistical model obtained fits well to the experimental data. The overall kinetic studies showed time was achieved after 5 h and caffeine adsorption followed the pseudo-second-order model suggesting chemisorption is a predominant mechanism. Redlich-Peterson and Sips models best represented the experimental data (0.967 < R² < 0.993). Thermodynamic revealed that caffeine adsorption was spontaneous at all temperatures studied, exothermic, and probably with changes in the adsorbate-adsorbent complex during the process. The tests conducted in different water matrixes corroborate the suitability of this adsorbent to be used in caffeine removal even in a complex solution.

Removal of caffeine, nicotine and amoxicillin from (waste)waters by various adsorbents. A review

The fast growth in the anthropogenic activities, that involve a wide use of pharmaceuticals, has led to the appearance of new toxic and hazardous chemical compounds, called "emerging pollutants", which could cause unpredictable consequences to the ecosystems. The current review is focused on emerging pollutants occurring in food or air and include caffeine and nicotine, as well as on pharmaceuticals, in particular amoxicillin, and the concerns caused by its wide usage for medical purposes. This review, for the first time, analyzes and discusses the potential risks and implications of caffeine, nicotine and amoxicillin as emerging environmental pollutants, a field that remains underrepresented to date. Both caffeine and nicotine belong to life style compounds, while pharmaceutical amoxicillin is one of the very popular β-lactam antibiotics used to take care of human and animal infections. The review covers the toxic effect caused by caffeine, nicotine and amoxicillin on humans and animals and describes some of the main adsorbents utilized for their removal (e.g., grape stalk, tea waste, wheat grains, bentonite, activated carbon, acid and base modified grape slurry wastes, graphene oxides, modified graphene oxides, zeolites, etc.). The isotherm and kinetic models for the analysis of caffeine, nicotine and amoxicillin adsorption by different adsorbents are presented. The impact of pH, temperature, adsorbent dosage and thermodynamic studies were deeply analyzed. The review also discusses the mechanism of adsorption for the above-mentioned emerging pollutants, which includes π-π interaction, cation-π bonding, electron-donor and electron-acceptor forces, van der Waals forces, electrostatic interactions, etc. The present review has a potential value for chemists, ecologists, toxicologists, environmental engineers, and other professionals that are involved in environmental protection.

Biochar from Fique Bagasse for Remotion of Caffeine and Diclofenac from Aqueous Solution

Caffeine and diclofenac are molecules with high human intake, and both belong to the ‘emergent’ class of contaminants. These compounds have been found at different concentrations in many sources of water worldwide and have several negative impacts on aquatic life systems; that is why the search for new alternatives for their removal from aqueous media is of transcendental importance. In this sense, adsorption processes are an option to attack this problem and for this reason, biochar could be a good alternative. In this regard, were prepared six different biochar from fique bagasse (FB), a useless agroindustry by-product from fique processing. The six biochar preparations were characterized through several physicochemical procedures, while for the adsorption processes, pH, adsorption time and concentration of caffeine and diclofenac were evaluated. Results showed that the biochar obtained by pyrolysis at 850 °C and residence time of 3 h, labeled as FB850-3, was the material with the highest adsorbent capacity with values of 40.2 mg g⁻¹ and 5.40 mg g⁻¹ for caffeine and diclofenac, respectively. It was also shown that the experimental data from FB850-3 fitted very well the Redlich–Peterson isotherm model and followed a pseudo-first and pseudo-second-order kinetic for caffeine and diclofenac, respectively.