Batch and fixed bed adsorption of levofloxacin on granular activated carbon from date (Phoenix dactylifera L.) stones by KOH chemical activation

Efficient adsorptive removal of levofloxacin using sulfonated graphene oxide: Adsorption behavior, kinetics, and thermodynamics

Water pollution by antibiotic residues poses a potential threat to environmental and human health. Graphene-based materials are highly stable, recyclable and effective adsorbents for efficiently removing antibiotics from polluted water. In this study, the adsorption behavior of levofloxacin onto sulfonated graphene oxide (SGO) was investigated by varying the contact period, solution pH, adsorbent quantity, levofloxacin concentration, inorganic ions, and solution temperature. Spectroscopic and microscopic techniques were employed to confirm the adsorptive interaction between levofloxacin and SGO. The adsorption process was most accurately characterized by the pseudo-second-order kinetic model and the Langmuir isotherm model, as indicated by their high correlation coefficients (R 2) and low root-mean-square error (RMSE) values. The maximal quantity of levofloxacin that can be adsorbed onto SGO was determined to be 1250 μmol/g at pH 4 and 25 °C using the Langmuir model. Thermodynamic studies reveal that the process of levofloxacin adsorption onto SGO is endothermic and spontaneous in nature. Taking into consideration the results of adsorption, desorption and regeneration studies, it is proposed that SGO can be applied as an economic viable agent for the adsorptive removal of levofloxacin from the aqueous environment.

Conversion of locally available materials to biochar and activated carbon for drinking water treatment

For environmental sustainability and to achieve sustainable development goals (SDGs), drinking water treatment must be done at a reasonable cost with minimal environmental impact. Therefore, treating contaminated drinking water requires materials and approaches that are inexpensive, produced locally, and effortlessly. Hence, locally available materials and their derivatives, such as biochar (BC) and activated carbon (AC) were investigated thoroughly. Several researchers and their findings show that the application of locally accessible materials and their derivatives are capable of the adsorptive removal of organic and inorganic contaminants from drinking water. The application of locally available materials such as lignocellulosic materials/waste and its thermo-chemically derived products, including BC and AC were found effective in the treatment of contaminated drinking water. Thus, this review aims to thoroughly examine the latest developments in the use of locally accessible feedstocks for tailoring BC and AC, as well as their features and applications in the treatment of drinking water. We attempted to explain facts related to the potential mechanisms of BC and AC, such as complexation, co-precipitation, electrostatic interaction, and ion exchange to treat water, thereby achieving a risk-free remediation approach to polluted water. Additionally, this research offers guidance on creating efficient household treatment units based on the health risks associated with customized adsorbents and cost-benefit analyses. Lastly, this review work discusses the current obstacles for using locally accessible materials and their thermo-chemically produced by-products to purify drinking water, as well as the necessity for technological interventions.

Arsenic removal adsorbent using limonite-polyethersulfone composite fiber via continuous flow column process

This research introduces an enhanced limonite-based composite fiber adsorbent for arsenic (As) removal. The modification involves creating polyethersulfone (PES)-limonite composite fibers loaded with 60 wt% limonite powders, designed to be applicable in water flow environments. The fibers were prepared using a wet-spinning process based on phase inversion, with varying concentrations (10, 20, and 30 wt%) of PES in NMP solution. The composite fiber with 10 wt% NMP exhibited a porous structure and demonstrated efficient absorption of both As(III) and As(V). Adsorption followed the Langmuir model, with qm values of 1.5 mg/g for As(III) and 3.2 mg/g for As(V) at pH 6. In column experiments, As removal rates increased with contact time, attributed to decreased flow rates (1 mL/min). Moreover, increasing fiber column height led to enhanced removal rates, as indicated by the Adams-Bohart model. The mechanism for As(V) removal involved the formation of an inner-sphere complex through ion exchange between α-FeOOH and HAsO4 - and H2 AsO4 2- in an aqueous solution at pH 6.8. PRACTITIONER POINTS: Changing the polyethersulfone ratio in the composite leads to variations in the appearance of limonite within each composite fiber. Limonite composite fibers effectively remove As(III) and As(V) at neutral pH. The adsorption behavior follows Langmuir kinetic model, the qm of 1.5 mg/g for As(III) and 3.2 mg/g for As(V). Longer columns and contact times enhance arsenic (As) removal in practical water treatment systems. Adam-Bohart model aids in predicting breakthrough and saturation time in As adsorption column design.

Rice husk coated with copper oxide nanoparticles for 17α-ethinylestradiol removal from an aqueous solution: adsorption mechanisms and kinetics

The 17 α-ethinylestradiol (EE2) adsorption from aqueous solution was examined using a novel adsorbent made from rice husk powder coated with CuO nanoparticles (CRH). Advanced analyses of FTIR, XRD, SEM, and EDSwere used to identify the classification parameters of a CRH-like surface morphology, configuration, and functional groups. The rice husk was coated with CuO nanoparticles, allowing it to create large surface area materials with significantly improved textural qualities with regard to functional use and adsorption performance, according to a detailed characterization of the synthesized materials. The adsorption process was applied successfully with elimination effectiveness of 100% which can be kept up to 61.3%. The parameters of adsorption were affecting the adsorption process significantly. Thermodynamic data stated that the process of adsorption was endothermic, spontaneous, chemisorption and the molecules of EE2 show affinity with the CRH. It was discovered that the adsorption process controlled by a pseudo-second-order kinetic model demonstrates that the chemisorption process was controlling EE2 removal. The Sips model is regarded as optimal for representing this practice, exhibiting a significantly high determination coefficient of 0.948. This coefficient implies that the adsorption mechanism indicates the occurrence of both heterogeneous and homogeneous adsorption. According to the findings, biomass can serve as a cheap, operative sorbent to remove estrogen from liquified solutions.

Sustainable functionalized smectitic clay-based nano hydrated zirconium oxides for enhanced levofloxacin sorption from aqueous medium

In this study, the functionalized smectitic clay (SC)-based nanoscale hydrated zirconium oxide (ZrO-SC) was successfully synthesized and utilized for the adsorptive removal of levofloxacin (LVN) from an aqueous medium. The synthesized ZrO-SC and its precursors (SC and hydrated zirconium oxide (ZrO(OH)₂)) were extensively characterized using various analytical methods to get insight into their physicochemical properties. The results of stability investigation confirmed that ZrO-SC composite is chemically stable in strongly acidic medium. The surface measurements revealed that ZrO impregnation to SC resulted in an increased surface area (six-fold higher than SC). The maximum sorption capacity of ZrO-SC for LVN was 356.98 and 68.87 mg g^-1 during batch and continuous flow mode studies, respectively. The mechanistic studies of LVN sorption onto ZrO-SC revealed that various sorption mechanisms, such as interlayer complexation, π-π interaction, electrostatic interaction, and surface complexation were involved. The kinetic studies of ZrO-SC in the continuous-flow mode indicated the better applicability of Thomas model. However, the good fitting of Clark model suggested the multi-layer sorption of LVN. The cost estimation of the studied sorbents was also assessed. The obtained results indicate that ZrO-SC is capable of removing LVN and other emergent pollutants from water at a reasonable cost.

Evaluation of acyclovir adsorption on granular activated carbon from aqueous solutions: batch and fixed-bed parametric studies

The present study is aimed to assess the adsorptive potential of carbonaceous material for the acyclovir (ACVR) removal from the aquatic environment using batch and fixed-bed processes. In batch mode, the impact of various process conditions (contact time, pH, adsorbent dose, initial ACVR concentration, and temperature) on ACVR adsorption was investigated. Experimental results revealed that Langmuir isotherm and the pseudo-second-order kinetic model adequately represent the ACVR adsorption mechanism, indicating homogeneous adsorption. The process was found exothermic and spontaneous. Thermodynamic studies concluded that adsorption is a result of both physisorption and chemisorption. To understand the dynamic regime for the design of large-scale column studies, experimental data obtained from breakthrough curve were fitted to various analytical kinetic models. Yan model followed by Thomas model demonstrated a greater correlation of breakthrough data, confirming that the results are significant and are in line with Langmuir isotherm and pseudo-second-order kinetic. G-AC exhibits sufficient adsorption capacity for ACVR. Hence, it is concluded that it can be used in a fixed-bed column in continuous mode for the treatment of ACVR-contaminated wastewater.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-023-02810-7.

Tuning cationic/anionic dyes sorption from aqueous solution onto green algal biomass for biohydrogen production

Global water security and energy demands associated with uncontrollable population growth and rapid industrial progress are one of the utmost serious needs dangerously confronting humanity. On account of waste as a wealth strategy; a multifunctional eco-friendly sorbent (MGAP) from green alga was prepared successfully for remediation of cationic/anionic organic dyes and biohydrogen production. The structural and morphological properties of sorbent were systematically scrutinized by a variety of spectral analyses. The loading capacity of MGAP towards rhodamine B (RhB) and methyl orange (MO) dyes was inclusivity inspected under variable experimental conditions. The adsorption kinetics of both dyes onto MGAP was in good agreement with pseudo-second-order theory, whereas adsorption isotherms could fit well with the Langmuir model, with satisfactory loading capacities of 144.92 and 196.04 mg g^-1 for RhB and MO molecules, respectively. Moreover, ultra-sonication treatment admirably decreased the sorption equilibrium time from 180.0 min to 30.0 min. Furthermore, spent sorbent was managed particularly for biohydrogen production with a measured yield of 112.89, 116.59, and 128.17 mL-H₂/gVS for MGAP, MGAP-MO, and MGAP-RhB, respectively. Overall, the produced MGAP can potentially be offered up as a promising dye scavenger for wastewater remediation and biohydrogen production, thereby fulfilling waste management and circular economy.

rGO-WO3 Heterostructure: Synthesis, Characterization and Utilization as an Efficient Adsorbent for the Removal of Fluoroquinolone Antibiotic Levofloxacin in an Aqueous Phase

Herein, the heterostructure rGO-WO₃ was hydrothermally synthesized and characterized by HRTEM (high-resolution transmission electron microscopy), FESEM (field emission scanning electron microscopy), XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron microscopy), nitrogen physisorption isotherm, Raman, TGA (thermogravimetric analysis) and zeta potential techniques. The HRTEM and FESEM images of the synthesized nanostructure revealed the successful loading of WO₃ nanorods on the surface of rGO nanosheets. The prepared heterostructure was utilized as an efficient adsorbent for the removal of a third-generation fluoroquinolone antibiotic, i.e., levofloxacin (LVX), from water. The adsorption equilibrium data were appropriately described by a Langmuir isotherm model. The prepared rGO-WO₃ heterostructure exhibited a Langmuir adsorption capacity of 73.05 mg/g. The kinetics of LVX adsorption followed a pseudo-second-order kinetic model. The adsorption of LVX onto the rGO-WO₃ heterostructure was spontaneous and exothermic in nature. Electrostatic interactions were found to have played a significant role in the adsorption of LVX onto the rGO-WO₃ heterostructure. Thus, the prepared rGO-WO₃ heterostructure is a highly promising material for the removal of emerging contaminants from aqueous solution.

Fixed bed column performance of Al-modified biochar for the removal of sulfamethoxazole and sulfapyridine antibiotics from wastewater

In this study, biochar derived from bamboo pretreated with aluminum salt was synthesized for the removal of two sulfonamide antibiotics, sulfamethoxazole (SMX) and sulfapyridine (SPY), from wastewater. Batch sorption experiments showed that Al-modified bamboo biochar (Al-BB-600) removed both sulfonamides effectively with the maximum sorption capacity of 1200-2200 mg/kg. The sorption mechanism was mainly controlled by hydrophobic, π-π, and electrostatic interactions. Fixed bed column experiments with Al-modified biochar packed in different dosages (250, 500 and 1000 mg) and flow rates (1, 2 and 4 mL/min) showed the dosage of 1000 mg and flow rate of 1 mL/min performed the best for the removal of both SMX and SPY from wastewater. Among the breakthrough (BT) models used to evaluate the fixed bed filtration performance of Al-BB-600, the Yan model best described the BT behavior of the two sulfonamides, suggesting that the adsorption process involved multiple rate-liming factors such as mass transfer at the solid surface and diffusion Additionally, the Bed Depth Service Time (BDST) model results indicated that Al-BB-600 can be efficiently used in fixed bed column for the removal of both SMX and SPY in scaled-up continuous wastewater flow operations. Therefore, Al-modified biochar can be considered a reliable sorbent in real-world application for the removal of SMX and SPY from wastewater.

Oxytetracycline co-metabolism with denitrification/desulfurization in SRB mediated system

Aquaculture wastewater contained a high remnant of oxytetracycline (OTC) and nitrate. In this study, OTC co-metabolized with denitrification/desulfurization was investigated in terms of kinetic analysis, pathway, microbial communities and produces analysis in sulfate-reducing bacteria (SRB) mediated system. Long-term acclimatization with sulfate (300 mg-S/L) could markedly accelerate the removed rate of OTC from 0.9 to 1.4 mg/g-SS/d, with the kinetic constants increasing from 0.2760 to 0.5232 d^-1, mainly via enzymes including adenosine-5'-phos-phosulfate reductase and cytochrome P450, and non-enzymatic process related to intermediates (adenosine-5'-phos-phosulfate and S⁰). Furthermore, OTC was likely detoxified by SRB enriched sludge mainly via hydrolysis, dehydration, oxidation and reduction. The denitrification process would postpone the OTC degradation via outcompeting electron donors with the desulfurization process. Redundancy analysis suggested that sulfur-oxidizing bacteria (Acidithiobacillus, Ochrobactrum) were highly related to OTC degradation processes. This study provides deep insight and a new opportunity for the treatment of aquaculture wastewater containing OTC, sulfate and nitrate by SRB sludge.

Comparative study on characteristics and mechanism of levofloxacin adsorption on swine manure biochar

This study evaluated the relationship between pyrolysis temperature (300-900 ℃), characteristics of swine manure (SM)-derived biochar (BC), and its adsorption of levofloxacin (LEV). The surface structure and chemistry of SM-derived BCs were characterized using Brunauer-Emmett-Teller analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. According to the characteristic analysis, the surface area and graphitization degree of SM-derived BC increased as temperature rose. The highest adsorption capacity was achieved by BC-900 (158 mg/g); this level was higher than that achieved in previous studies and comparable to that of commercial activated carbons. Characterization and adsorption experiments indicated that pore-filling, π-π stacking interaction, π-π electron donor-acceptor, H-bonding, and hydrophobic interactions each played a critical role in the adsorption of LEV on SM-derived BC. Collectively, this study confirms the potential utility of SM-derived BC for the removal of antibiotics.

Adsorbent Minimization for Removal of Ibuprofen from Water in a Two-Stage Batch Process

Pharmaceutical products in water, also known as personal pharmaceutical products or PCPPs, are developing contaminants that have the potential to impair human health and the environment in a variety of ecosystems. In this work, waste date stones, a waste product obtained from the seedless dates manufacturing industry, were used to make acid-activated carbon. This material has been utilized to extract the medicinal component ibuprofen from water, with a high adsorption capacity of 126 mg ibuprofen per g of waste date stone-generated activated carbon. A design study was conducted to minimize the amount of activated carbon required, utilizing a two-stage batch adsorption system to optimize the usage of the activated carbon. To test the model and compare the quantities of adsorbent required in the two-stage and single-stage systems under various conditions, several variables were entered into the design model.

Three porous shapeable three-component hydrogen-bonded covalent-organic aerogels as backfill materials in a simulated permeable reactive barrier (PRB) for trapping levofloxacin

Levofloxacin (LEV) infiltrated in groundwater has threatened the safety of drinking water. For in-situ remediation of LEV-contaminated groundwater, there exists a main challenge of exploiting proper high efficient backfill medium in utilizing charming permeable reactive barriers (PRBs). Herein, three porous shapeable three-component hydrogen-bonded covalent organic aerogels (H_COA-1, H_COA-2 and H_COA-3) were fabricated based on a multiple-linking-site strategy to evaluate for adsorptive removal of LEV. The three H_COAs exhibited satisfactory performance in LEV adsorption that could integrate high adsorption capacity, good antiion interference, excellent recyclability and wide pH tolerance. The different regularity of kinetics and isotherms of three H_COAs signified that electrostatic effect, pore preservation, hydrogen bonding probably govern the adsorption process in combination, coupling with π-π electron-donor-acceptor (EDA), dipole-dipole and hydrophobic-hydrophobic interaction besides. In addition, the response surface methodology (RSM) was employed for studying the single and synergetic effects of selected variables and optimizing operation conditions. Furthermore, a laboratory PRB column packed with processable H_COA-2 was set up to investigate the LEV removal, and the breakthrough data was explained by Adams-Bohart, Thomas, BDST and Yoon-Nelson models. We believe could hopefully bring H_COAs into the real in-situ remediation of such challenging and persistent LEV-polluted groundwater with further massive-scale efficiently.

Hierarchical hollow-tubular porous carbon microtubes prepared via a mild method for supercapacitor electrode materials with high volumetric capacitance

In this paper, hollow-tubular porous carbons were synthesized from abundant biomass Cycas fluff (CF) through simple carbonization followed by an NaHCO₃ mild activation process. After activation, the tubular structure of the CF was retained, and a hierarchical structure of micropores, mesopores and macropores was formed. When the optimal mass ratio of NaHCO₃/CF is 2, the obtained porous carbon CF-HPC-2 sample has a large specific surface area (SSA) of 516.70 m² g⁻¹ in Brunauer–Emmett–Teller (BET) tests and a total pore volume of 0.33 cm³ g⁻¹. The C, O, N and S contents of CF-HPC-2 were tested as 91.77 at%, 4.09 at%, 3.54 at%, and 0.6 at%, respectively, by elemental analysis. Remarkably, CF-HPC-2 exhibits a high volume capacitance (349.1 F cm⁻³ at 1 A g⁻¹) as well as a higher rate capability than other biomass carbon materials (289.1 F cm⁻³ at 10 A g⁻¹). Additionally, the energy density of the CF-HPC-2 based symmetric supercapacitor in 2 M Na₂SO₄ electrolyte at 20 kW kg⁻¹ is 27.72 W h kg⁻¹. The particular hollow tubular morphology and activated porous structure determine the excellent electrochemical performance of the material. Hence, this synthetic method provides a new way of storing energy for porous carbon as high volumetric capacitance supercapacitor materials.

In this paper, hollow-tubular porous carbons were synthesized from abundant biomass Cycas fluff (CF) through simple carbonization followed by an NaHCO₃ mild activation process.

New mechanistic insight into rapid adsorption of pharmaceuticals from water utilizing activated biochar

The presence of emerging pollutants especially hazardous chemicals and pharmaceuticals in aquatic environments is a matter of grave concern to human health and the environment. In this study, coffee bean waste (CBW) was utilized to synthesize pristine (CBW₅₅₀) and activated (CBW₅₅₀^HPO) biochars for the elimination of diclofenac (DF) and levofloxacin (LEV) from water. A facile two-step approach was used to synthesize CBW₅₅₀^HPO using chemical pretreatment and pyrolysis under N₂ purging. BET results of CBW₅₅₀^HPO revealed that chemical pretreatment increased surface area by approximately 160 times compared to CBW₅₅₀. The calculated I_D/I_G ratio from Raman spectra confirmed that CBW₅₅₀^HPO had a high functionalized surface. Different operational parameters such as contact time, pH, adsorbent dose, ionic strength, and adsorbate concentration were studied and optimized. Maximum Langmuir adsorption capacity of CBW₅₅₀^HPO was found to be 61.17 and 110.70 mg/g for DF and LVX, respectively. Experimental results demonstrated that presence of NaCl in solution enhanced DF removal efficiency due to the salting-out effect. Electrostatic attraction, π-π bonding, and hydrophobic interaction were prominently responsible mechanisms for the adsorption of DF and LVX. Furthermore, continuous-flow mode studies confirmed that CBW₅₅₀^HPO can be successfully utilized in large-scale treatment applications.

Adsorption of pharmaceuticals in a fixed-bed column using tyre-based activated carbon: Experimental investigations and numerical modelling

Magnetic tyre char (MTC), activated tyre char (ATC) and commercial activated carbon (CAC) were used as packing materials in lab-scale column study for the adsorption of three pharmaceuticals: propranolol (PRO), ciprofloxacin (CIP) and clomipramine (CLO), from aqueous solution. The obtained breakthrough curves (BTCs) suggest that, lower flow rate, greater bed height, higher pH and nano particle size led to increased adsorption of PRO. The lowest adsorption capacity was observed for CIP either from single or ternary solution while it was significantly higher for CLO. Surface area of ATC increased nearly twelve-fold (38.17 to 453.81 m²/g), after thermal and chemical activation and adsorption capacity was comparable to commercial activated carbon. The suitability of Hydrus-1D model incorporating chemical non-equilibrium process to simulate the pharmaceutical transport and fit experimental BTCs was demonstrated (97.29 <R² <99.22) in comparison to other common models (Adams-Bohart, Thomas and Yoon-Nelson). The modelling suggests the existence of non-equilibrium conditions and rate-limited sorption sites and the effect of dispersion and mass transfer mechanisms in the solute transport under dynamic conditions. The cost analysis showed that unit cost for treatment of wastewater using fixed-bed columns of tyre char was calculated to be 1.57 US$/m³ which can be deemed as commercially feasible.

Carbon-based adsorbents for fluoroquinolone removal from water and wastewater: A critical review

This review summarizes the adsorptive removal of Fluoroquinolones (FQ) from water and wastewater. The influence of different physicochemical parameters on the adsorptive removal of FQ-based compounds is detailed. Further, the mechanisms involved in the adsorption of FQ-based antibiotics on various adsorbents are succinctly described. As the first of its kind, this paper emphasizes the performance of each adsorbent for FQ-type antibiotic removal based on partition coefficients of the adsorbents that is a more sensitive parameter than adsorption capacity for comparing the performances of adsorbents under various adsorbate concentrations and heterogeneous environmental conditions. It was found that π-π electron donor-acceptor interactions, electrostatic interactions, and pore-filling were the most prominent mechanisms for FQ adsorption by carbon and clay-based adsorbents. Among all the categories of adsorbents reviewed, graphene showed the highest performance for the removal of FQ antibiotics from water and wastewater. Based on the current state of knowledge, this review fills the gap through methodolically understanding the mechanism for further improvement of FQ antibiotics adsorption performance from water and wastewater.

Elimination of organochlorine pesticides from water by a new activated carbon prepared from Phoenix dactylifera date stones

This work focused on the characterization of activated carbon (AC) prepared by pyrolysis-chemical activation with phosphoric acid (60%) from date stones derived from three categories of date palm Phoenix dactylifera (Ajwa, Anbari, Khudri), and on its feasibility of elimination of organochlorine pesticides (OCPs) in water samples. The obtained results showed that the three-produced AC date stone had developed a porous structure, large specific surface area, and acidic property. Due to the high SBET (> 1200 m²/g), Ajwa stones activated coal was considered as the best AC that can be used for the adsorption of environmental contaminants. The effects of several parameters such as the Ajwa AC dose, the time of contact, the initial concentration of pesticides, and the pH were evaluated. The results showed that the adsorption balance of organochlorine pesticides on this AC was reached after a contact time of 60 min at an optimal pHzpc equal to 2. In addition, 0.4 g of AC was the best quantity found to retain the largest quantity of pesticides while considering the economic part.

Removal of Acid Red 88 Using Activated Carbon Produced from Pomelo Peels by KOH Activation: Orthogonal Experiment, Isotherm, and Kinetic Studies

Activated carbon (PPAC) from pomelo peels was prepared by carbonization and KOH activation. The performance of PPAC was assessed by removing acid red 88 (AR88) in aqueous solution. The most suitable activation processes were found by orthogonal experiments, aimed to achieve the maximum of removal capacity of AR88. Moreover, the possible mechanisms of adsorption were studied through the results of characterization, isotherm fitting, and kinetics simulation. Results showed the preparation parameter that mattered the most to AR88 removal efficiency was the activation temperature of PPAC, followed by impregnation ratio and activation time. The optimal preparation conditions of PPAC were at activation temperature 800°C, activation time 90 min, and impregnation ratio 2.5 : 1. The characterization results showed optimal PPAC had a microporous and amorphous carbon structure whose BET specific area and total pore volume were 2504 m2/g and 1.185 cm3/g, respectively. The isotherm fitting demonstrated that the sorption process followed the Langmuir model, and theoretical maximal sorption value was 1486 mg/g. The kinetics simulation showed that the pseudo-second-order model described the sorption behavior better, suggesting chemisorption seemed to be the rate-limiting step in the adsorption process. This work presented that PPAC was a promising and efficient adsorbent for AR88 from water.

Simultaneous removal of antibiotic and nutrients via Prosopis juliflora activated carbon column: Performance evaluation, effect of operational parameters and breakthrough modeling

In this study, the behavior of mono-component (metronidazole/phosphate/nitrate, MET/PO₄^3-/NO₃^-) and multi-component (MET+PO₄^3-+NO₃^-) adsorption in fixed-bed adsorption column was investigated using Prosopis juliflora activated carbon (PJAC). The influence of column operating parameters such as bed depth (H: 5-15 cm), influent flow rate (Q: 0.5-2 L/h) and adsorbate concentration (C_o: 25-100 mg/L) on breakthrough curves were evaluated. The experimental data was correlated with breakthrough models viz. Thomas, Adams-Bohart, Yoon-Nelson and bed depth service time (BDST) models. The results showed that the Thomas model fitted the experimental data better than other models in predicting the breakthrough characteristics for the removal of MET, PO₄^3- and NO₃^- by PJAC. The maximum adsorption capacity found by Thomas model was 9.70, 8.21 and 5.57 mg/g for MET, PO₄^3- and NO₃^-, respectively. In multi-component systems, antagonistic behavior in sorption of MET, PO₄^3- and NO₃^- was observed and as a result, adsorption capacity was 1.2-1.5 folds lesser than that observed in mono-component system. In conclusion, results of the present study indicate that the PJAC can be successfully employed for the removal of MET, PO₄^3- and NO₃^- using fixed-bed adsorption column; however, the column design for multi-component mixture should be based on rapid breakthrough sorbate.

Current State of Porous Carbon for Wastewater Treatment

Porous materials constitute an attractive research field due to their high specific surfaces; high chemical stabilities; abundant pores; special electrical, optical, thermal, and mechanical properties; and their often higher reactivities. These materials are currently generating a great deal of enthusiasm, and they have been used in large and diverse applications, such as those relating to sensors and biosensors, catalysis and biocatalysis, separation and purification techniques, acoustic and electrical insulation, transport gas or charged species, drug delivery, and electrochemistry. Porous carbons are an important class of porous materials that have grown rapidly in recent years. They have the advantages of a tunable pore structure, good physical and chemical stability, a variable specific surface, and the possibility of easy functionalization. This gives them new properties and allows them to improve their performance for a given application. This review paper intends to understand how porous carbons involve the removal of pollutants from water, e.g., heavy metal ions, dyes, and organic or inorganic molecules. First, a general overview description of the different precursors and the manufacturing methods of porous carbons is illustrated. The second part is devoted to reporting some applications such using porous carbon materials as an adsorbent. It appears that the use of porous materials at different scales for these applications is very promising for wastewater treatment industries.

Biocarbon Derived from Opuntia ficus indica for p-Nitrophenol Retention

Activated carbon obtained from Opuntia ficus indica by sodium hydroxide activation was employed for the adsorption of p-nitrophenol from water. The activated carbons obtained were characterized by Fourier transforms infrared spectroscopy, sorption of nitrogen, scanning electron microscopy, and Boehm titration. Effects of pH, contact time, amount of adsorbent, and temperature on the adsorption of p-nitrophenol were studied. Adsorption isotherms were analyzed using Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich models, and the thermodynamic parameters have been determined. The adsorption of p-nitrophenol was spontaneous, exothermic, and propitious at 15 °C and adopted the pseudo-second order model, and the most credible isotherm was Langmuir’s one. The activated carbon used in this work has good p-nitrophenol adsorption characteristics, and the study of the desorption and reuse of this carbon shows that it retains a removal rate greater than 94% after five cycles of adsorption-desorption.

Instantaneous oxidation of levofloxacin as toxic pharmaceutical residuals in water using clay nanotubes decorated by ZnO (ZnO/KNTs) as a novel photocatalyst under visible light source

Kaolinite nanotubes were synthesized by a simple scrolling process and decorated by ZnO nanoparticles as a novel nanocomposite (ZnO/KNTs). The synthetic ZnO/KNTs composite was characterized as an effective photocatalyst in the oxidation of levofloxacin pharmaceutical residuals in the water resources. The composite displays a surface area of 95.4 m²/g, average pore diameter of 5.8 nm, and bandgap energy of 2.12 eV. It is of high catalytic activity in the oxidation of levofloxacin in the presence of visible light source. The complete oxidation for 10 mg/L of levofloxacin was recognized after 55 min, 45 min, and 30 min with applying 30 mg, 40 mg, and 50 mg of ZnO/KNTs as catalyst dosage, respectively. Additionally, it achieved complete oxidation for 20 mg/L and 30 mg/L of levofloxacin after 45 min and 75 min, respectively using 50 mg as catalyst dosage. The degradation efficiency was confirmed by detecting the residual TOC after the treatment tests and the formed intermediate compounds were identified to suggest the degradation pathways. In addition to the oxidation pathway, the mechanism was evaluated based on the active trapping tests that proved the dominance of hydroxyl radicals as the essential active species. Finally, the ZnO/KNTs composite is of promising recyclability properties and achieved better results than several studied photocatalysts in literature.

Ibuprofen sorptive efficacy of zirconium caged date seed derived steam activated alginate beads in a static bed column

The sorption capability of zirconium coupled sodium alginate beads of steam activated biochar derived from date seed (Zr(DSPB)Al) was explored towards Ibuprofen (IBP) removal from simulated water solution in a static bed column. The impact of governing variables viz. column bed height (5–25 cm), influent (IBP) concentration (10–30 mg L⁻¹) and inflow rate (2–6 mL min⁻¹) was investigated in the present study. The column experimentation reflected that with an increase in column bed length, the breakthrough curve height was increased. The maximum sorbent uptake was found to be 23.33 mg g⁻¹ from an optimal column bed height of 20 cm, influent (IBP) concentration of 30 mg L⁻¹ and inflow rate of 2 mL min⁻¹ with the achievement of 94.86% of IBP removal. The bed depth service model (BDST) was studied to examine the sorbent's efficacy and it was observed that column bed height was one of the effective factors towards effective IBP sorption. The Yoon–Nelson model and Thomas model corroborated extremely well with the experimental findings. The desorption study presented a sorbent efficiency up to 5 cycles for IBP exclusion with 37.59% regeneration of the column. The investigation indicated that the novel sorbent Zr(DSPB)Al with proficient performance could be successfully applied for IBP elimination from aqueous solutions.

The sorption capability of zirconium coupled sodium alginate beads of steam activated biochar derived from date seed (Zr(DSPB)Al) was explored towards Ibuprofen (IBP) removal from simulated water solution in a static bed column.

Prediction of adsorption capacity for pharmaceuticals, personal care products and endocrine disrupting chemicals onto various adsorbent materials

Adsorption is a common process used to remove pharmaceuticals, personal care products and endocrine disrupting chemicals (PPCPs/EDCs) from water. However, as PPCPs/EDCs cover a wide range of molecules and chemical structures, prediction of the adsorption capacity is very challenging. In this study, a novel model was developed to predict adsorption isotherms of PPCPs/EDCs onto various types of adsorbents using a combination of Polanyi potential theory, molecular connectivity indices (MCIs) and molecular characteristics. Polanyi theory provided the basic mathematical form for the correlation. MCIs, hydrophobicity and H-bond count were used to normalize the Polanyi equation based on the molecular structure and interactions among the chemicals, the adsorbents, and the solution. In total, adsorption data were collected from 158 reports for 55 PPCPs/EDCs onto 306 different adsorbent materials. The correlation was first trained with 46 PPCPs/EDCs adsorbed onto 162 carbonaceous adsorbents (CAs), with 44.8% SDEV. Then the model was employed to predict 46 PPCPs/EDCs onto 118 other CAs and 9 new PPCPs/EDCs onto 23 CAs in ultrapure water, with error from 42 to 48% SDEV. When applying to non-carbonaceous adsorbents, the models can still predict the adsorption of PPCPs/EDCs with 90.09% SDEV. For the first time, a model, the PD - MCI - hydrophobic - H bond model, was developed to predict adsorption of a wide group of complicated PPCPs/EDCs onto a big variety of carbonaceous and non-carbonaceous adsorbents. The proposed model approach may provide a simple means for predicting adsorption capacities of PPCPs/EDCs onto various adsorbents.

Adsorption and oxidation of ciprofloxacin in a fixed bed column using activated sludge derived activated carbon

In this study, the performance of activated sludge derived granular activated carbon (SGAC) was investigated for ciprofloxacin (CPX) removal from synthetic and simulated wastewaters in a fixed-bed adsorption column operated in continuous mode. The adsorbent was synthesized using chemical activation using ZnCl₂ as activating agent. Its surface area and pore volume were found comparable to that of the commercial granular activated carbon (CGAC). The maximum saturation adsorption capacities for CPX were ~16 mg/g and ~14 mg/g, respectively, with SGAC column under identical operating conditions (CPX concentration = 50 mg/L, bed height = 4 cm and wastewater flow rate = 1.5 mL/min) for synthetic and simulated wastewaters. The presence of other organics reduced CPX adsorption capacity of SGAC. The breakthrough curve data for both wastewaters could be adequately fit in Thomas and Yoon-Nelson kinetic models. The addition of H₂O₂ in wastewater showed no considerable improvement in CPX removal. However, H₂O₂ oxidation of spent adsorbent exhibited better results compared to thermal treatment for adsorbent regeneration. The results showed that sewage sludge can be recycled as an efficient adsorbent for the removal of recalcitrant organic pollutants from wastewater.

Removal of aqueous fluoroquinolones with multi-functional activated carbon (MFAC) derived from recycled long-root Eichhornia crassipes: batch and column studies

Fluoroquinolones (FQs) occur broadly in natural media due to its extensive use, and it has systematic effects on our ecosystem and human immunity. In this study, long-root Eichhornia crassipes was reclaimed as a multi-functional activated carbon (MFAC) to remove fluoroquinolones (FQs) from contaminated water. To get insight into the adsorption mechanism, multiple measurements, including FTIR and XPS analyses, were employed to investigate the adsorption processes of ciprofloxacin and norfloxacin as well as the experiments of effect of exogenous factors on adsorption performances. The results confirmed that the adsorption of FQs by MFAC was mainly attributed to the electrostatic interaction, hydrogen bond interaction, and electronic-donor-acceptor (EDA) interaction. In addition, the kinetics and thermodynamics experiments demonstrated that the MFAC possessed great adsorption performance for FQs. According to the Langmuir model, the saturated adsorption capacities exceeded 145.0 mg/g and 135.1 mg/g for CIP and NOR at 303.15 K, respectively. The column experiments were conducted to explore the application performance of MFAC on the advanced treatment of synthetic water at different flow rates and bed depths. The adsorption capacity of CIP on MFAC was estimated by the Thomas models and the bed-depth service time (BDST) models, reaching 127.56 mg/g and 11,999.52 mg/L, respectively. These results also provide a valid approach for the resource recycling of the redundant long-root Eichhornia crassipes plants. Graphical abstract.

Fe3+ enhanced degradation of oxytetracycline in water by pseudomonas

The application and fate of antibiotics are closely related to human health and the ecological balance, which has gradually aroused the widespread global concerns. Long-term antibiotic residues can easily induce antibiotic resistance and antibiotic resistance genes (ARGs) in the environment. Although many studies have investigated the metabolic pathways of biosynthesis or degradation of oxytetracycline (OTC) and its influencing factors under laboratory or controlled conditions, the understanding of OTC degradation pathways and influencing factors in the environment is still poor. In the present study, the role of Pseudomonas (T4) in OTC biodegradation were investigated with different carbon sources, metal ions, substrate concentrations, temperatures, and pH values, as well as the temporal changes in the relative abundance of OTC ARGs. It was found that OTC could be degraded by T4 as a sole carbon source. Comparison with Cu²⁺, the addition of Fe³⁺ could significantly promote the growth of T4, and then increased the OTC degradation percentage to 65.3%. The initial concentration of OTC, temperature, and pH had significant impacts on OTC degradation. At the initial OTC concentration of 50 mg L^-1, the percentage degradation of OTC by T4 could reach 81.0% at the presence of Fe³⁺, and at 40 °C and pH = 7. Common tetracycline ARGs were not found during the OTC degradation by T4 in the present study. The eight main putative OTC degradation byproducts were identified by ultra-high definition accurate-mass quadrupole time-of-flight tandem mass spectrometry (QTOF/MS). Six different reaction types and seven possible degradation pathways were proposed, including enol-ketone conversion, hydroxylation, dehydration, deamination, demethylation and decarbonylation. Under optimal conditions, the OTC degradation percentages by T4 could reach to 88.2%, 91.6% and 92.0% in pond water, fish wastewater and industrial wastewater, respectively. These results demonstrate the high effectiveness of T4 at the presence of Fe³⁺ for the enhanced biodegradation of OTC in water environment, without resulting in the occurrence of ARGs. This has important implications for the removal of OTC from aquatic environments by the technology proposed from this study.

Removal of acetaminophen from synthetic wastewater in a fixed-bed column adsorption using low-cost coconut shell waste pretreated with NaOH, HNO3, ozone, and/or chitosan

Acetaminophen (Ace) is a trace pollutant widely found in sewage treatment plant (STP) wastewater. We test the feasibility of coconut shell waste, a low cost adsorbent from coconut industry, for removing Ace from synthetic solution in a fixed-bed column adsorption. To enhance its performance, the surface of granular activated carbon (GAC) was pre-treated with NaOH, HNO₃, ozone, and/or chitosan respectively. The results show that the chemical modification of the GAC's surface with various chemicals has enhanced its Ace removal during the column operations. Among the modified adsorbents, the ozone-treated GAC stands out for the highest Ace adsorption capacity (38.2 mg/g) under the following conditions: 40 mg/L of Ace concentration, 2 mL/min of flow rate, 45 cm of bed depth. Both the Thomas and the Yoon-Nelson models are applicable to simulate the experimental results of the column operations with their adsorption capacities: ozone-treated GAC (20.88 mg/g) > chitosan-coated GAC (16.67 mg/g) > HNO₃-treated GAC (11.09 mg/g) > NaOH-treated GAC (7.57 mg/g) > as-received GAC (2.84 mg/g). This suggests that the ozone-treated GAC is promising and suitable for Ace removal in a fixed-bed reactor.

Adsorption of basic and reactive dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon: batch and column study

The adsorption behavior of basic, methylene blue (MB), and reactive, remazol brilliant violet 5R (RBV), dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon (IBSAC) was executed via batch and column studies. The produced activated carbon was characterized through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch studies were performed to investigate the effects of contact time, initial concentration, and solution pH. The equilibrium data for both MB and RBV adsorption better fits Langmuir model with maximum adsorption capacity of 434.78 and 212.77 mg/g, respectively. Kinetic studies for both MB and RBV dyes showed that the adsorption process followed a pseudo-second-order and intraparticle diffusion kinetic models. For column mode, the breakthrough curves were plotted by varying the flow rate, bed height, and initial concentration and the breakthrough data were best correlated with the Yoon-Nelson model compared to Thomas and Adams-Bohart model. The adsorption activity of IBSAC shows good stability even after four consecutive cycles.

Removal of emerging pharmaceutical contaminants by adsorption in a fixed-bed column: A review

Pharmaceutical pollutants substantially affect the environment; thus, their treatments have been the focus of many studies. In this article, the fixed-bed adsorption of pharmaceuticals on various adsorbents was reviewed. The experimental breakthrough curves of these pollutants under various flow rates, inlet concentrations, and bed heights were examined. Fixed-bed data in terms of saturation uptakes, breakthrough time, and the length of the mass transfer zone were included. The three most popular breakthrough models, namely, Adams-Bohart, Thomas, and Yoon-Nelson, were also reviewed for the correlation of breakthrough curve data along with the evaluation of model parameters. Compared with the Adams-Bohart model, the Thomas and Yoon-Nelson more effectively predicted the breakthrough data for the studied pollutants.