Magnetic nanocomposite of filamentous algae activated carbon for efficient elimination of cephalexin from aqueous media

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.

Performance evaluation of facile synthesized CA-PVA-GO composite for the mitigation of Cr(Ⅲ) and C.I. acid violet 54 dye from tannery wastewater

Untreated tannery wastewater contains a large amount of toxic metals, dyes, and other pollutants, which pose adverse effects on the ecosystem and public health. In this work, a calcium alginate-poly vinyl alcohol-graphene oxide (CA-PVA-GO) composite was prepared to remove metals and dyes, particularly Cr(Ⅲ) and CI acid violet 54 (AV54) dye, from tannery wastewater. FESEM, FTIR, and XRD analyses were applied to characterize the GO and CA-PVA-GO. Different operational variables, viz. pH (3.0-5.5 for Cr(III) and 2-7 for dye), dosage (0.164-2.46 g/L), contact time (10-60 min), initial concentration (39, 65, 98, and 201 ppm for Cr(III) and 21.5, 38.5, 54.5, and 61.75 ppm for dye), and temperature (298, 308, 318, and 328 K) were studied to evaluate the efficiency of the CA-PVA-GO composite. The optimum conditions for Cr(Ⅲ) and AV54 dye adsorption were found to be pH (5.0 and 3.0), dosage (0.82 g/L for both), and time (45 and 60 min), respectively, with 35.35 ± 1.43% and 84.63 ± 2.54% removal efficiency. The experimental data was analyzed through the Langmuir and Freundlich isotherms. The maximum adsorption capacity (qm) was observed at 173.01 and 74.68 mg/g for Cr(Ⅲ) and AV54 dye, respectively. The pseudo-second-order kinetic model was fitted better (R2 = 0.981, 0.995, 0.92, and 0.995) than first-order for AV54 dye adsorption. Thermodynamic analyses revealed that the Cr(Ⅲ) and AV54 dye adsorption processes were spontaneous and exothermic. The value of Gibbs free energy (ΔG) for Cr(III) adsorption was obtained at -7.433, -4.508, -2.626, and -1.311 kJ/mol, whereas it was -5.178, -4.867, -4.628, and -4.555 kJ/mol for dye. The values of ΔH and ΔS were -67.257 and -0.198 kJ/mol for Cr(III) and -10.852 and -0.019 kJ/mol for the dye removal. The regenerated CA-PVA-GO composite was reused successfully. Different physicochemical parameters, viz., concentration, pH, TDS, EC, BOD5, and COD of chrome tanning and dyeing effluents, were analyzed before and after the adsorption. The results of chromium and dye removal from tannery wastewater were 53.18% and 93.91%, revealing that the developed eco-friendly CA-PVA-GO composite could be an operative adsorbent for tannery wastewater treatment and possibly scaled up to an industrial level.

Degradation of levofloxacin using electro coagulation residuals-alginate beads as a novel heterogeneous electro-fenton composite

The presence of levofloxacin (LEV) in aqueous solutions can pose health risks to humans, have adverse effects on aquatic organisms and ecosystems, and contribute to the development of antibiotic-resistant bacteria. This study aims to investigate the feasibility of using electrocoagulation residuals (ECRs) as a heterogeneous catalyst in the electro-Fenton process for degrading LEV. By combining electrocoagulation residuals with sodium alginate, ECRs-alginate beads were synthesized as a heterogeneous electro-Fenton composite. The response surface method was employed to investigate the optimization and influence of various operating parameters such as the initial concentration of LEV (10-50 mg/L), voltage (15-35 V), pH (3-9), and catalyst dose (1-9 g/L). The successful incorporation of iron and other metals into the ECRs-alginate beads was confirmed by characterization tests such as EDX and FTIR. By conducting a batch reaction under optimal conditions (initial LEV concentration = 20 mg/L, pH = 4.5, voltage = 30V, and catalyst dose = 7 g/L), a remarkable degradation of 99% for LEV was achieved. Additionally, under these optimal conditions, a high removal efficiency of 92.3% for total organic carbon (TOC) could be attained within 120 min and these findings are remarkable compared to previous studies. The results further indicated that the degradation of levofloxacin (LEV) could be accurately quantified by utilizing the first-order kinetic reaction with a 0.03 min-1 rate constant. The synthesized beads offered notable advantages in terms of being eco-friendly, simple to use, highly efficient, and easily recoverable from the liquid medium after use.

Isotherms, kinetics and thermodynamic mechanism of methylene blue dye adsorption on synthesized activated carbon

The treatment of methylene blue (MB) dye wastewater through the adsorption process has been a subject of extensive research. However, a comprehensive understanding of the thermodynamic aspects of dye solution adsorption is lacking. Previous studies have primarily focused on enhancing the adsorption capacity of methylene blue dye. This study aimed to develop an environmentally friendly and cost-effective method for treating methylene blue dye wastewater and to gain insights into the thermodynamics and kinetics of the adsorption process for optimization. An adsorbent with selective methylene blue dye adsorption capabilities was synthesized using rice straw as the precursor. Experimental studies were conducted to investigate the adsorption isotherms and models under various process conditions, aiming to bridge gaps in previous research and enhance the understanding of adsorption mechanisms. Several adsorption isotherm models, including Langmuir, Temkin, Freundlich, and Langmuir-Freundlich, were applied to theoretically describe the adsorption mechanism. Equilibrium thermodynamic results demonstrated that the calculated equilibrium adsorption capacity (qe) aligned well with the experimentally obtained data. These findings of the study provide valuable insights into the thermodynamics and kinetics of methylene blue dye adsorption, with potential applications beyond this specific dye type. The utilization of rice straw as an adsorbent material presents a novel and cost-effective approach for MB dye removal from wastewater.

Persulfate-assisted heterogeneous photocatalytic degradation of furfural from aqueous solutions using TiO2-ZnO/biochar composite

This study evaluated the performance of TiO2-ZnO/biochar as activator of persulfate (PS) for degradation of furfural. After the successful synthesis of the catalyst, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) methods were used to investigate the properties of TiO2-ZnO/biochar. The findings of this research suggests that under optimal conditions (pH = 3, catalyst dosage = 1 g/L, persulfate concentration = 1.2 mM, and furfural concentration = 10 mg/L), the PS/Catalysts/UV system can remove 96 % of furfural within 15 min. Under ideal conditions, the experimental results fit well with the first-order kinetic model (R2 > 0.95), and the rate constant (Kobs) was derived as 0.195 min-1. The quenching experiments provided further insights that confirmed the participation of SO4°- and OH° radicals in the degradation process. Nevertheless, the evidence strongly supports the idea that SO4°- plays a more prominent and dominant role as the primary radical species responsible for furfural degradation. Based on the obtained results, it can be concluded that the PS/Catalysts/UV system has an appropriate ability to remove furfural from aqueous solutions, which suggests promising perspectives for its practical application in pollutant treatment scenarios.

Biogenic adsorbents for removal of drugs and dyes: A comprehensive review on properties, modification and applications

This comprehensive review explores the potential and versatility of biogenic materials as sustainable and environmentally benign alternatives to conventional adsorbents for the removal of drugs and dyes. Biogenic adsorbents derived from plants, animals, microorganisms, algae and biopolymers have bioactive compounds that interact with functional groups of pollutants, resulting in their binding with the sorbent. These materials can be modified mechanically, thermally and chemically to enhance their adsorption properties. Biogenic hybrid composites, which integrate the characteristics of more than one material, have also been fabricated. Additionally, microorganisms and algae are analyzed for their ability to uptake pollutants. Various influential factors that contribute to the adsorption process are also discussed. The challenge, limitations and future prospects for research are reviewed and bridging gap between large scale application and laboratory scale. This comprehensive review, involves a combination of various biogenic adsorbents, going beyond the existing literature where typically only specific adsorbents are reported. The review also covers the isotherms, kinetics, and desorption studies of biogenic adsorbents, providing an improved framework for their effective use in removing pharmaceuticals and dyes from wastewater.

Exploitation of expired cellulose biopolymers as hydrochars for capturing emerging contaminants from water

Expired chemicals pose a potential environmental threat to humans and living organisms. Herein, we proposed a green approach whereby expired cellulose biopolymers were converted to hydrochar adsorbents and tested for removing the emerging pharmaceutical contaminants of fluoxetine hydrochloride and methylene blue from water. A thermally stable hydrochar was produced with an average particle size of 8.1 ± 1.94 nm and a mesoporous structure that exhibited a larger surface area than the expired cellulose by 6.1 times. The hydrochar was efficient in removing the two contaminants with efficiencies that reached above 90% under almost neutral pH conditions. Adsorption exhibited fast kinetics and regeneration of the adsorbent was successful. The adsorption mechanism was hypothesized in view of the Fourier Transform Infra-Red (FTIR) spectroscopy and pH effect measurements to be mainly electrostatic. A hydrochar/magnetite nanocomposite was also synthesized, and its adsorption behavior for both contaminants was tested and it revealed an enhanced percent removal relative to the bare hydrochar by 27.2% and 13.1% for FLX and MB, respectively. This work supports the strategies for zero waste management and the circular economy.

Modeling, optimization and efficient use of MMT K10 nanoclay for Pb (II) removal using RSM, ANN and GA

Regarding the long-term toxic effects of Pb (II) ions on human health and its bioaccumulation property, taking measures for its reduction in the environment is necessary. The MMT-K₁₀ (montmorillonite-k₁₀) nanoclay was characterized by XRD, XRF, BET, FESEM, and FTIR. The effects of pH, initial concentrations, reaction time, and adsorbent dosage were studied. The experimental design study was carried out with RSM-BBD method. Results prediction and optimization were investigated with RSM and artificial neural network (ANN)-genetic algorithm (GA) respectively. The RSM results showed that the experimental data followed the quadratic model with the highest regression coefficient value (R² = 0.9903) and insignificant lack of fit (0.2426) showing the validity of the Quadratic model. The optimal adsorption conditions were obtained at pH 5.44, adsorbent = 0.98 g/l, concentration of Pb (II) ions = 25 mg/L, and reaction time = 68 min. Similar optimization results were observed by RSM and artificial neural network-genetic algorithm methods. The experimental data revealed that the process followed the Langmuir isotherm and the maximum adsorption capacity was 40.86 mg/g. Besides, the kinetic data indicated that the results fitted with the pseudo-second-order model. Hence, the MMT-K₁₀ nanoclay can be a suitable adsorbent due to having a natural source, simple and inexpensive preparation, and high adsorption capacity.

Adsorption and separation of Cs(I) and Ba(II) from aqueous solution using zinc ferrite-humic acid nanocomposite

Reclaimable adsorbents have an essential role in removing radionuclides from waste streams. Herein, zinc ferrite-humic acid ZFO/HA nanocomposite was synthesized for effective cesium and barium adsorption. The prepared ZFO/HA nanocomposite was analyzed using analytical techniques including XRD, FTIR, EDX, and SEM. From kinetic studies, the mechanism adsorption process follows the second model. The isotherm studies clarified that the Langmuir model fit the adsorption of both ions onto the prepared sample, and the monolayer capacities are equal to 63.33 mg/g and 42.55 mg/g for Ba(II) and Cs(I), respectively. The temperature parameter was also studied, and the adsorption reaction was spontaneous and endothermic. The maximum separation between two ions was achieved at pH 5 (αCs/Ba = 3.3).

2,4-Dichlorophenoxyacetic acid (2,4-D) adsorptive removal by algal magnetic activated carbon nanocomposite

In the present study, ferric oxide nanoparticles impregnated with activated carbon from Ulva prolifera biomass (UPAC-Fe₂O₃) were prepared and employed to remove 2,4-Dichlorophenoxyacetic acid (2,4-D) by adsorption. The UPAC-Fe₂O₃ nanocomposite was characterized for its structural and functional properties by a variety of techniques. The nanocomposite had a jagged, irregular surface with pores due to uneven scattering of Fe₂O₃ nanoparticles, whereas elemental analysis portrayed the incidence of carbon, oxygen, and iron. XRD analysis established the crystalline and amorphous planes corresponding to the iron oxide and carbon phase respectively. FT-IR analyzed the functional groups that confirmed the integration of Fe₂O₃ nanoparticles onto nanocomposite surfaces. VSM and XPS studies uncovered the superparamagnetic nature and presence of carbon and Fe₂O_3, respectively, in the UPAC-Fe₂O₃ nanocomposite. While the surface area was 292.51 m²/g, the size and volume of the pores were at 2.61 nm and 0.1906 cm³/g, respectively, indicating the mesoporous nature and suitability of the nanocomposites that could be used as adsorbents. Adsorptive removal of 2,4-D by nanocomposite for variations in process parameters like pH, dosage, agitation speed, adsorption time, and 2,4-D concentration was studied. The adsorption of 2,4-D by UPAC-Fe₂O₃ nanocomposite was monolayer chemisorption owing to Langmuir isotherm behavior along with a pseudo-second-order kinetic model. The maximum adsorption capacity and second order rate constant values were 60.61 mg/g and 0.0405 g/mg min respectively. Thermodynamic analysis revealed the spontaneous and feasible endothermic adsorption process. These findings confirm the suitability of the synthesized UPAC-Fe₂O₃ nanocomposite to be used as an adsorbent for toxic herbicide waste streams.

Cephalexin removal by a novel Cu-Zn bionanocomposite biosynthesized in secondary metabolic products of Aspergillus arenarioides EAN603 with pumpkin peels medium: Optimization, kinetic and artificial neural network models

The present study aimed to investigate the removal efficiency of cephalexin (CFX) by a novel Cu-Zn bionanocomposite biosynthesized in the secondary metabolic products of Aspergillus arenarioides EAN603 with pumpkin peels medium (CZ-BNC-APP). The optimization study was performed based on CFX concentrations (1, 10.5 and 20 ppm); CZ-BNC-APP dosage (10, 55 and 100 mg/L); time (10, 55 and 100 min), temperature (20, 32.5 and 45 °C). The artificial neural network (ANN) model was used to understand the CFX behavior for the factors affecting removal process. The CZ-BNC-APP showed an irregular shape with porous structure and size between 20 and 80 nm. The FTIR detected CC, C-O and OH groups. ANN model revealed that CZ-BNC-APP dosage exhibited the vital role in the removal process, while the removal process having a thermodynamic nature. The CFX removal was optimized with 12.41 ppm CFX, 60.60 mg/L of CZ-BNC-APP, after 97.55 min and at 35 °C, the real maximum removal was 95.53% with 100.52 mg g^-1 of the maximum adsorption capacity and 99.5% of the coefficient. The adsorption of CFX on CZ-BNC-APP was fitted with pseudo-second-order model and both Langmuir and Freundlich isotherms models. These findings revealed that CZ-BNC-APP exhibited high potential to remove CFX.

Sustainable approaches for removal of cephalexin antibiotic from non-clinical environments: A critical review

In this article, the removal of cephalexin (CFX) antibiotic from non-clinical environment is reviewed. Adsorption and photocatalytic degradation techniques are widely used to remove CFX from waters and wastewaters, the combination of these methods is becoming more common for CFX removal. The treatment methods of CFX has not been reviewed before, the present article aim is to organize the scattered available information regarding sustainable approaches for CFX removal from non-clinical environment. These include adsorption by nanoparticles, bacterial biomass, biodegradation by bacterial enzymes and the photocatalysis using different catalysts and Photo-Fenton photocatalysis. The metal-organic frameworks (MOFs) appeared to have high potential for CFX degradation. It is evident from the recently papers reviewed that the effective methods could be used in place of commercial activated carbon. The widespread uses of photocatalytic degradation for CFX remediation are strongly recommended due to their engineering applicability, technical feasibility, and high effectiveness. The adsorption capacity of the CFX is ranging from 7 mg CFX g^-1 of activated carbon nanoparticles to 1667 mg CFX g^-1 of Nano-zero-valent iron from Nettle. In contrast, the photo-degradation was 45% using Photo-Fenton while has increased to 100% using heterogeneous photoelectro-Fenton (HPEF) with UVA light using chalcopyrite catalyst.

Evaluating the Removal of the Antibiotic Cephalexin from Aqueous Solutions Using an Adsorbent Obtained from Palm Oil Fiber

This study aimed to understand the adsorption process of cephalexin (CPX) from aqueous solution by a biochar produced from the fiber residue of palm oil. Scanning electron microscopy, Fourier transform infrared spectroscopy, Boehm titration, and the point of zero charge were used to characterize the morphology and surface functional groups of the adsorbent. Batch tests were carried out to evaluate the effects of the solution pH, temperature, and antibiotic structure. The adsorption behavior followed the Langmuir model and pseudo-second-order model with a maximum CPX adsorption capacity of 57.47 mg g^-1. Tests on the thermodynamic behavior suggested that chemisorption occurs with an activation energy of 91.6 kJ mol^-1 through a spontaneous endothermic process. Electrostatic interactions and hydrogen bonding represent the most likely adsorption mechanisms, although π-π interactions also appear to contribute. Finally, the CPX removal efficiency of the adsorbent was evaluated for synthetic matrices of municipal wastewater and urine. Promising results were obtained, indicating that this adsorbent can potentially be applied to purifying wastewater that contains trace antibiotics.

Kinetics, isotherms, effect of structure, and computational analysis during the removal of three representative pharmaceuticals from water by adsorption using a biochar obtained from oil palm fiber

Acetaminophen (ACE), cephalexin (CPX), and valsartan (VAL) are recognized water pollutants, which can be removed by adsorption. Herein, the removal of these pharmaceuticals using a biochar (BP), prepared from oil palm fiber, was tested. It was studied the structural effects of the pharmaceuticals and biochar on the adsorption process supported by experimental and computational results, plus characterizations of the material. The biochar has 76.05 m² g^-1 of surficial area, and carboxylic groups (1.343 mmol g^-1) predominantly. The maximum adsorption uptakes were 7.3, 7.9, and 23.85 mg g^-1 for ACE, CPX, and VAL, respectively; following pseudo-second-order kinetics. The best pollutants removal was obtained at acidic pH (3.0). Computational analyses indicated that oxygenated groups of BP (able to generate H-bond interactions) influenced the adsorption of pharmaceuticals. It can be remarked that BP is a low-cost adsorbent synthesized easily from wastes, with high feasibility to remove pharmaceutical structures from water.

Adsorption of methylene blue dye from aqueous solution by a novel PVA/CMC/halloysite nanoclay bio composite: Characterization, kinetics, isotherm and antibacterial properties

Here the fabrication of a novel PVA/CMC/halloysite nanoclay membrane for the effective adsorption of cationic dye (methylene blue, MB) from aqueous environment is reported. The membranes were analyzed through scanning electron microscopy (SEM), optical microscopy (OM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), contact angle and universal testing machine (UTM) analysis. The adsorption behavior of the membrane in terms of nanoclay loading, contact time, initial concentration of MB, pH and temperature were also discussed. The membrane exhibits excellent removal efficiency (99.5%) for MB in the optimal conditions such as nanoclay dose = 6 wt%, initial dye concentration = 10 ppm, contact time = 240 min, pH = 10 and temperature = 30 °C. Three isotherm models (Freundlich, Langmuir and Temkin) were employed to analyze the dye adsorption data. The results revealed that the adsorption process could be described well with both Freundlich and Langmuir isotherm model. The kinetics of MB adsorption onto membrane follows pseudo-second-order model while thermodynamic parameter indicate that adsorption is feasible and endothermic in nature. The antibacterial studies revealed that the PVA/CMC/halloysite nanoclay membrane possess notable antibacterial property. Finally, the desorption studies showed that the membrane have good reusability even after four recycles.

Single-step pyrolysis for producing magnetic activated carbon from tucumã (Astrocaryum aculeatum) seed and nickel(II) chloride and zinc(II) chloride. Application for removal of nicotinamide and propanolol

The present research describes the synthesis of new nanomagnetic activated carbon material with high magnetization, and high surface area prepared in a single pyrolysis step that is used for the carbonization, activation, and magnetization of the produced material. The pyrolysis step of tucumã seed was carried out in a conventional tubular oven at 600 °C under N₂-flow. It was prepared three magnetic carbons MT-1.5, MT-2.0, MT-2.5, that corresponds to the proportion of biomass: ZnCl₂ always 1:1 and varying the proportion of NiCl₂ of 1.5, 2.0, and 2.5, respectively. These magnetic nanocomposites were characterized by Vibrating Sample Magnetometer (VSM), X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, hydrophobic/hydrophilic balance, CHN/O elemental analysis, modified Boehm titration, N₂ adsorption-desorption isotherms; and pH_pzc. All the materials obtained presented Ni particles with an average crystallite size of less than 33 nm. The MT-2.0 was employed for the removal of nicotinamide and propranolol from aqueous solutions. Based on Liu isotherm, the Q_max was 199.3 and 335.4 mg g^-1 for nicotinamide and propranolol, respectively. MT-2.0 was used to treat simulated pharmaceutical industry effluents attaining removal of all organic compounds attaining up to 99.1 % of removal.