Contact Time Research Articles

Recovery of Cu from waste smelting slag through extraction with novel deep eutectic solvents (DESs)

ABSTRACT This study reports on the recovery of copper, zinc, and iron from the copper smelting slag (CSS) of Saindak Copper and Gold Project, Baluchistan, Pakistan using novel deep eutectic solvents (DESs) and Sulfuric acid. Sorbic acid, citric acid, and urea were each mixed with tetrabutylammonium chloride (TBAC) to prepare three DESs. Leaching experiments were performed in batch mode under a constant stirring speed of 300 revolutions per minute (rev min−1) and contact time of 2 h, under different liquid to solid ratios (L/S 1.5–3) and different temperatures (60–90°C). Results showed that the DES2 (TBAC & citric acid) recovered about 77% copper, 49% zinc, and 1% iron among other two prepared DESs at 3 L/S and 90°C. Sulphuric acid recovered 94% copper, 2% zinc, and 4.7% iron under the same conditions. The same DES also showed selectivity in the recovery of copper, as compared to iron.

Adsorptive Removal of Famotidine Drug from Aqueous Medium by Ocimum Basilicum

AbstractThe present study investigated the potential of basil seeds as adsorbent in order to remove famotidine drug from aqueous media. The optimum conditions for the adsorption of famotidine on the basil seeds were found to be 50 min contact time, 50 °C temperature, pH 1, 100 ppm concentration of famotidine, 0.03 g adsorbent mass and 50 rpm agitation rate. Pseudo 2nd order kinetics with a higher correlation coefficient (R2=0.9942) suggested chemisorption as preferable mechanism of adsorption. However, the enthalpy of adsorption (ΔH=+33.67 KJ/mol) was less than that of chemisorption but higher than that of physisorption which was attributed to strong hydrogen bonding between famotidine molecules and basil seed surface. The Langmuir isotherm with higher R2 (0.9960) than Freundlich isotherm (R2=0.8798) predicted maximum adsorption capacity (qm) of 99 mg/g while suggesting monolayer and favourable adsorption. The adsorption was endothermic (+ΔH) and spontaneous (−ΔG) in nature. The FT‐IR spectroscopy confirmed that famotidine was adsorbed on basil seed via strong hydrogen bonding. The study proposed that the simultaneous intake of famotidine and basil seeds should be strictly avoided as the drug readily adsorbs on basil seeds in acidic environment (gastric pH) thereby reducing its curing effect.

Experimental study and analysis of CO2 and SO2 absorption in various water-based nanofluids by response surface methodology

The absorption of acidic gases in the oil and gas industries is important due to their toxicity and corrosive effects. Recently, the application of nanofluids based on aqueous or organic solvents as absorbents has been examined by a variety of researchers. In this study, a single bubble column was exploited to study the effect of water-based nanofluids on the absorption processes of SO2 and CO2 using response surface methodology (RSM) based on Box-Behnken three-level experiment design. With this in mind, CO2 and SO2 are separately injected at the bottom of a bubble column filled with one of the nanofluids: Al2O3-water, SiO2-water, or ZnO-water for each experiment. Then, the rate of SO2 or CO2 absorption in the nanofluids has been elucidated. The effect of important parameters including the weight fraction of the nanoparticles (NPs) (0.01, 0.055, and 0.1 wt.%), gas–liquid contact time (150, 300, and 450 s), and the diameter of nozzle for gas injection (0.46, 0.57, and 0.68 mm) have been studied. Results revealed that the maximum molar flux of both gases was observed in the ZnO-water nanofluid, followed by the SiO2-water nanofluid. In addition, increasing the nanoparticle mass fraction and the bubble size causes the molar flux to rise. However, increasing the gas–liquid contact time causes the molar flux of the mentioned gases to decrease. Finally, a set of the accurate equations has been proposed to predict the molar flux of SO2 and CO2 in the various nanofluids assessed in this work.

An analysis of the contact time of nanodroplets impacting superhydrophobic surfaces with square ridges

Reducing the contact time between liquid droplets and solid surfaces is important in numerous engineering applications. Mechanisms for reducing the contact time have been extensively studied. However, there is still a lack of systematic research on the mechanisms governing the changes in the contact time of nanodroplets impacting superhydrophobic surfaces with square ridges. Additionally, there has been relatively little examination of the differences between nanodroplets and macroscopic droplets in this scenario. In this work, we investigate the impact of nanodroplets on both superhydrophobic planes and superhydrophobic surfaces with square ridges. When nanodroplets impact a superhydrophobic plane, we find that the droplet contraction time determines the total contact time. When nanodroplets impact superhydrophobic surfaces with square ridges, we find for the first time that the critical factor determining its contact time is the detachment time of the droplet from the square ridges as it lifts off. Compared to millimeter-sized droplets, nanodroplets exhibit stronger adhesion to solid surfaces. Additionally, we propose for the first time that nanodroplets are more resistant to deformation and splitting. We define the Weber number (We) at which the droplet rebounds as the critical rebound Weber number (We), and use this to evaluate the effect of square ridges on improving droplet rebound. We observe that a moderate increase in the square ridge height is beneficial to reducing the contact time. By altering the square ridge width, we find that a narrower ridge is more favorable for reducing the contact time and for facilitating droplet splitting.

Rebound dynamics of multiple droplets symmetrically/asymmetrically impacting macrotextured superhydrophobic surfaces

The rebound dynamics of multiple impinging droplets is investigated and compared under the symmetrical and asymmetrical impact conditions. The result shows that at various relative velocities, when multiple droplets symmetrically impinge macrotextured superhydrophobic surfaces, the rebound modes consist of the left–right non-simultaneous rebound (LRNSR), the coalescence-split simultaneous rebound (CSSR) and the right-left non-simultaneous rebound (RLNSR). With the transition of rebound modes, the contact time is first reduced under the LRNSR mode and then constant under the CSSR and RLNSR modes as the relative velocity is increased. Whereas when multiple droplets asymmetrically impinge macrotextured superhydrophobic surfaces, the rebound modes consist of the left-ridge-right rebound (LRIRR), the left–right-ridge rebound (LRRIR) and LRNSR. When the relative velocity is increased, the contact time is first reduced under the LRIRR mode and then constant under the LRRIR mode. But under the LRNSR mode, the first reduced and then constant contact time appears with increased relative-velocities.

Natural and environmentally friendly rhamnolipid functionalized luffa fibers for adsorptive removal of pharmaceutical contaminant: Batch and fixed-bed column studies

This study aims to explore the potential of utilizing rhamnolipid functionalized luffa fibers as an environmentally sustainable solution for removing pharmaceutical contaminants from water. The efficiency of the developed adsorbent for removing acetaminophen has been investigated in batch and fixed bed column modes. The adsorbent has been characterized via FTIR, XRD, and SEM analyses which revealed the rhamnolipid nanomicelles formation with bi-pyramidal morphology and the presence of functional groups on the surface of the adsorbent. The optimum conditions have been reported (pH: 5.0, adsorbent dosage 2 g/L, initial acetaminophen concentration: 20 mg/L, and contact time: 80 min). The highest adsorption capacity for acetaminophen was 37.03 mg/g at the optimized conditions. Fixed-bed column experiments examined flow rate and initial acetaminophen concentration effects, with the Thomas model assessing column performance. This research investigates the potential of RL-LF for effective water remediation, offering insights into practical applications and optimization strategies.

Electrolytic synthesis of γ-Al2O3 nanoparticle from aluminum scrap for enhanced methylene blue adsorption: experimental and RSM modeling

The presence of methylene blue (MB) dye in wastewater has raised concern about human health and environmental ecology due to potential carcinogenic, and mutagenic effects. Therefore, this work aims to remove MB dye from wastewater using γ-Al2O3 nanoparticles synthesized from aluminum scrap via simple electrolytic method. The successful synthesis of the adsorbent was confirmed by a range of spectroscopy and microscopy techniques, including XRD, SEM, FTIR, and BET. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimize the processing parameters such as solution pH, contact time, initial MB concentration, and adsorbent dose. The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of MB dye (R2 = 0.9862). The optimum condition for the maximum MB dye removal (98.91%) was achieved at solution pH of 8.298, initial MB concentration of 31.657 mg/L, adsorbent dose of 0.387 g/L, and contact time of 46.728 min. Nano-γ-Al2O3 was shown to have a good surface area of 59 mg2/g by BET analysis. The adsorption kinetics follows the pseudo-second-order model (R2 = 0.997). With a maximum adsorption capacity of 137.17 mg/g, the Langmuir isotherm model (R2 = 984) provides the best fit to the adsorption isotherm data, indicating a monolayer adsorption process. Furthermore, thermodynamic analysis demonstrated that the adsorption of MB dye was an endothermic and spontaneous process. The reusability study showed that γ-Al2O3 nano-adsorbent retained 85.08% of its original removal efficiency after five cycles. According to the findings of the study, MB dye molecules were taken up by γ-Al2O3 nano-adsorbent via hydrogen bond formation, Van der Waals interaction, and electrostatic attraction. Therefore, γ-Al2O3 nanoparticles can be used as a potentially eco-friendly and low-cost adsorbent for the removal of MB dye from aqueous solutions.

Kinetic Studies and Adsorption of Fluoride from Drinking Water using Tamarind Shell as Adsorbent

The excessive intake of fluoride in drinking water is a serious health concern in most of the states in India and in the world. The regular consumption of drinking water containing fluoride leads to a disease called as fluorosis. The Present work of this paper explores the removal of fluoride from synthesized aqueous solution of fluoride using Tamarind fruit shell powder. The Adsorption of fluoride by Tamarind fruit shell is cost effective method and gives high efficiency than other adsorbents. In the present study, The pretreatment for moisture removal from the tamarind shell powder given also we have shown the Kinetics and comparative study to find highest fluoride removal efficiency. In the Kinetic study, the the controlling parameters for adsorption like pH, Adsorbent concentration, Contact time relation on the removal efficiency is studied. The data obtained is fitted in the Langmuir and Freundlich Adsorption Isotherms. The work shows the selective adsorbing property of tamarind shell powder for fluoride removal. The comparison of removal efficiency of fluoride by using tamarind shell powder with wheat straw is done

Enhanced performance of amine and thiol chemically modified graphene oxide for effective removal of Hg(II), Pb(II), and Cr(VI) from aqueous solution

This study describes a novel adsorbent with a multidentate ligand that was facilely fabricated by covalently bonding 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole on graphene oxide (AHMT-PRGO). The AHMT-PRGO nano-adsorbent was used for the effective removal of Hg(II), Pb(II), and Cr(VI) from wastewater. The AHMT-PRGO nano-adsorbent was synthesized by a nucleophilic substitution reaction between GO acyl chloride and AHMT chelating ligand in the presence of tetrabutyl-ammonium bromide as a catalyst. The successful modifications were confirmed via several spectroscopic and electron microscopy instrumentations including UV–Vis, FTIR, Raman, XRD, XPS, SEM, and TEM. The maximum adsorption capacities of Hg(II), Cr(VI), and Pb(II) on the AHMT-PRGO nano-adsorbent were 370.0, 136.2, and 109.6 mg/g, respectively, exceeding those of most previously reported adsorbents. Additionally, the equilibrium contact times for Hg(II), Pb(II), and Cr(VI) were 60, 30, and 400 min, respectively. In a mixture of nine heavy metal ions containing 250 ppm of each ion, the AHMT-PRGO nano-adsorbent exhibited high selectivity for Hg(II) ions. Furthermore, the AHMT-PRGO nano-adsorbent showed high stability over five adsorption–desorption cycles. Additionally, the AHMT-PRGO nano-adsorbent was successfully applied to remove heavy metal ions from real water samples. The novelty of AHMT-PRGO lies in the combination of a multidentate ligand for strong and selective binding with the high surface area and stability offered by covalently bonded graphene oxide. This combination offers potential advantages over traditional adsorbents in terms of adsorption capacity, selectivity, and reusability.

A potential thermosensitive poloxamer 407-based in situ hydrogel containing moxifloxacin-loaded silk fibroin nanoparticles for prolonged ocular delivery

The aim of this study was to develop a hybrid system of thermosensitive poloxamer 407-based in situ hydrogel containing moxifloxacin-loaded silk fibroin nanoparticles (MFX-FNPs ISG) for improving the residence time of the antibacterial drug on the eye. Moxifloxacin-loaded silk fibroin nanoparticles (MFX-FNPs) were successfully formulated by absorption technique and two optimized poloxamer 407-based in situ hydrogels (ISG) were prepared by cold method. Consequently, the MFX-FNPs dispersion was embedded into these in situ hydrogels and sterilized by autoclave. Optimized MFX-FNPs displayed an average particle size of 210 nm, zeta potential of -30 mV, and moderate entrapment efficiency ∼ 44%. The hybrid system of MFX-FNPs ISG possessed homogeneous solutions with acceptable osmolality, optimal pH levels, and transmittance of ∼ 90% and manifested a pseudoplastic flow behavior at 35 °C. Furthermore, they exhibited a solution form at room temperature and quickly transformed into gel at ocular temperature. The in vitro release of MFX from MFX-FNPs ISG showed a prolonged drug release following Peppas-Sahlin kinetic model. Interestingly, the in vitro mucoadhesive study revealed that the combination systems significantly increased the residence time of the particles on the mucus membrane over 6 h compared to the solution and nanodispersion form. The prepared formulations showed effective antibacterial activity against both Staphylococcus aureus and Pseudomonas aeruginosa without causing toxicity to human corneal epithelial cells, suggesting no ocular irritation. Therefore, the MFX-FNPs ISG offer the potential to enhance the contact time of moxifloxacin on the ocular surface, thus improving the therapeutic efficacy in treating bacterial keratitis.

Micro-particle-clay aided microporous support for removal of hydrocarbon toxicity from petroleum refinery wastewater in single-slope solar distillation

The removal of toxic hydrocarbon pollutants is not sustainable via conventional treatment technology. This research investigates the feasibility of a solar distillation (SSD) system to eliminate soluble hydrocarbon salts, stubborn organics, and separation of oil emulsion from petroleum refinery wastewater (PRW). The PRW collected from the petroleum refinery facility and hydrophilic micro-particle clay (MP-clay) samples were characterized following the ASTM and SEM techniques. The treatment process for the removal of total dissolved salts (TDS), biological oxygen demand (BOD), and separation of oil emulsion was monitored in the SSD still using MP-clay aided microporous filter support, at varying MP-clay concentrations (0.5–3.5 mg/L), pH (6.6–7.3), temperature (27–80 0C), and exposure time (1–18hrs) respectively. The results showed MP-clay as self-assembled monolayers on microporous support with a 98 % reduction in BOD concentration under optimum conditions: pH of 7.3, contact time of 9 hours, and MP-clay concentration of 3.2 mg/L. The TDS concentration decreased by 94 % at the optimal exposure time (15hrs) and temperature (48 0C) in SSD still. The investigation also examined the recyclability of MP-clay for oil content accumulation and water separation. The findings demonstrated MP-clay on reuse retained 90.5 % of its activity in water separation and established MP-clay can be operated to the optimum of 3 cycles, each lasting 60 minutes. After this period, reactivity loss becomes severe owing to lipase leakage and substrate obstruction. The research findings will help harness solar energy for environmentally friendly and cost-effective PRW remediation.

The impact of simulation-based learning on the knowledge, attitude and performance of physiotherapy students on practice placement

BackgroundPractice placement is a crucial part of pre-registration physiotherapy education worldwide. However, educators face challenges in finding practice sites for students to undertake placement. The use of simulation-based (SBL) learning has the potential to replace some traditional placement, thereby increasing placement capacity, but the benefits have not been fully explored. This study aimed to assess the impact of SBL placement on students’ knowledge, attitude, and performance during practice placements with external providers.MethodsThis study utilised an exploratory qualitative research design using a semi-structured interview to collect data from Year 2 students of a 2-year MSc pre-registration physiotherapy programme in the UK. To be eligible to be included in the study, students must have participated in the 4-week simulation placement and have completed all their practice placements with external providers. All the interviews were conducted virtually in a 1:1 setting and recorded. The interviews lasted an average of 45 min. An inductive thematic analysis based on Braun and Clarke’s approach was utilised in this study.ResultsTwelve students consented to participate in this study. The 56 codes generated from the data were categorised into 5 themes; [1] Working together, [2] Working with Service Users, [3] Professionalism, [4] Profession-specific practical skills and [5] Generic practical skills. Participants unanimously expressed a positive view on working in groups, and they believe that engaging with service users who acted as patients enhanced the authenticity of the simulation placement. Subjective and objective assessments were considered important profession-specific skills gained during the simulation. Despite the benefits derived from the simulation placement, some participants felt that the learning experience would have been enriched by periodically changing the groups they were working in and having the opportunity for more 1:1 feedback throughout the four weeks.ConclusionsSBL has the potential to be a valuable educational experience for physiotherapy students. It may assist in better preparing students for successful integration into the dynamic healthcare environment. To enhance and improve the authenticity of this type of placementour recommendations include recruiting more service users, incorporating and encouraging more intervention-based elements, and increasing the practice educators’ and students’ contact time.

Magnetic pomegranate peels activated carbon (MG-PPAC) composite for Acid Orange 7 dye removal from wastewater

A magnetic pomegranate peels activated carbon (MG-PPAC) nanocomposite (23.46–26.75 nm) was prepared as an effective adsorbent for Acid Orange 7 (AO7) dye removal from wastewater. The effects of impregnation ratio and activation temperatures (600–900 °C) on the specific surface area and pore morphology were studied. BET, SEM, EDX, FT-IR, XRD and VSM are considered the synthesized composite MG-PPAC. The prepared magnetic composite at 700 °C activation temperature and impregnation ratio 1/2 (peels/ZnCl2) exhibited 513.34 m2/g surface area, 0.4025 cm3/g volume of the total pores, and 3.1364 nm mean diameter of the pores. The magnetization saturation, remanence and coercivity of the MG-PPA composite were 14.116 emu/g, 0.50685 emu/g, and 19.705 G, respectively. Also, the composite MG-PPAC was in a super-paramagnetic state at room temperature and could be gathered within 5 S (less than 5 S) with an external magnetic field. The impact of pH, adsorbent dose, initial concentration of adsorbate (AO7 dye), and time of contact have been studied to optimize the removal process. Langmuir, Freundlich and Temkin isotherm models were used to investigate MG-PPAC adsorption behavior for AO7 dye. Applicability of the Langmuir isotherm model demonstrates a monolayer adsorption AO7 dye removal process, and the maximum monolayer capacity (Qm) attained from linear solvation of LIM is 322.58 mg/g. Furthermore, the highest removal was 99.53% at pH 2.25. Also, the adsorption process was tested using like pseudo-first-order, pseudo-second-order, intraparticle diffusion, film diffusion, and Elovich models. The pseudo-second-order model is well-fitted to the operational data of AO7 dye removal.

Review of the occurrence, treatment technologies, and detection methods for saxitoxins in freshwaters

ABSTRACT The increasing occurrence of saxitoxins in freshwaters is becoming a concern for water treatment facilities owing to its structural properties which make it resistant to oxidation at pH &amp;lt; 8. Hence, it is crucial to be able to monitor these toxins in surface and drinking water to protect public health. This review aims to outline the current state of knowledge related to the occurrence of saxitoxins in freshwaters and its removal strategies and provide a critical assessment of the detection methods to provide a basis for further development. Temperature and nutrient content are some of the factors that influence the production of saxitoxins in surface waters. A high dose of sodium hypochlorite with sufficient contact time or activated carbon has been shown to efficiently remove extracellular saxitoxins to meet the drinking water guidelines. While HILIC-MS has proven to be a powerful technology for more sensitive and reliable detection of saxitoxin and variants after solid phase extraction, ELISA is cost-effective and easy to use and is used by Ohio EPA for surveillance with a limit of detection of 0.015 μg/L. However, there is a need for the development of cost-effective and sensitive techniques that can quantify the variants of saxitoxin.

Box-Behnken Design for Mitigation of Cadmium Bivalent Ions from Aqueous Medium.

Statistical analysis is essential for minimizing the time, cost, and number of experiments needed to get the maximum output. In this work, the removal of cadmium bivalent (Cd (II)) ions was optimized using Box-Behnken design methodology. The effects of pH, concentration, time, and temperature were investigated for the removal of cadmium. Maximum removal (85.70%) was achieved at pH of 5.34, initial Cd(II) ions concentration 46.61,contact time 166.09 (min), and at 59.40 oC temperature on Punica Granatum carpellary membrane powder (PGCMP) and 88.61% removal was achieved on its modified forms (MPGCMP) at pH of 5.79, initial Cd(II) ions concentration 65.70,contact time 178.96, and at 59.91 oC temperature. The model was validated by analyzing variance (ANOVA). The practical data was well fitted to the quadratic model. PGCMP and MPGCMP were found to be naturally occurring, environmentally friendly adsorbents for the mitigation of Cd (II) ions as well as other toxic heavy metals from drinkable or wastewater.

An Experimental and Theoretical Investigation on Highly Reusable Visible Light Active CoTe Nanosheets for Improved Photocatalytic Degradation of Toxic Aniline Blue Dye

AbstractSemiconductor‐assisted photocatalytic treatment is among the most effective methods for eliminating persistent contaminants from industrial wastewater. This study presents a hydrothermal approach for the preparation of Cobalt Telluride (CoTe) nanosheets for the degradation of aniline blue dye under visible light irradiation. The synthesized catalyst was characterized using various techniques, including X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, RAMAN spectroscopy, high‐Resolution transmission electron microscopy (HRTEM), and X‐ray photoelectron spectroscopy (XPS). Tauc's model was used to determine the optical band gap. The key operating parameters, such as the amount of CoTe, initial aniline blue (AB) concentration, and contact time, have been optimized to achieve the highest AB degradation percentage. Under visible light, 98 % of dye degradation occurred within 60 minutes. The degradation process was further assessed using total organic carbon (TOC) measurements. Free‐radical capture experiments were conducted to identify the role of radical species in the photocatalytic process. The photocatalytic process revealed that the equilibrium data aligns well with the Langmuir‐Hinshelwood kinetic model. A rate constant of 0.03486 min−1 was obtained. The photocatalyst demonstrated excellent recyclability, maintaining efficiency and structural integrity over five cycles. The photocatalytic experiment results also have been confirmed by a density functional theory (DFT) calculation.

Development of a Novel Cyclodextrin-Chitosan Polymer for an Efficient Removal of Pharmaceutical Contaminants in Aqueous Solution.

A novel polymer synthesized by grafting three cyclodextrins onto chitosan was characterized and evaluated for its potential to adsorb two pharmaceutical residues: ibuprofen and progesterone. The influence of various operational parameters, including contact time, initial molecule concentration, pH, ionic strength, and temperature, was investigated. The synthesized polymer exhibits an amorphous and porous structure with a remarkable swelling capacity of 9.5 mmol/g. It demonstrates remarkable adsorption capacities for progesterone and ibuprofen, reaching 90% and 75%, respectively. Kinetic studies reveal that the adsorption of both molecules follows a pseudo-second-order model. A DSC analysis elucidated the adsorption mechanism, which is governed by the formation of inclusion complexes and electrostatic interactions within the polymer network. The polymer's regeneration after 23 cycles demonstrates its sustainable adsorption efficiency. The combination of chitosan with three cyclodextrins opens up promising new avenues for water treatment and the removal of specific pollutants. This approach significantly improves the material's selectivity towards target pollutants, offering a significant advantage in pollution remediation applications.

Design and Construction and Energy Consumption Study of a New Electrolyzed Water Cell Generator Prototype for Food Disinfection

This study explores the feasibility of producing electrolyzed water (EW) for post-harvest treatment of fruits and vegetables as a new substitute for current chemical products. A prototype generator using tap water and NaCl solution was tested for EW’s sanitization efficiency, energy, and economic costs. In vitro tests on Penicillium e., Aspergillus n., Botrytis c., and Alternaria a. assessed EW pH, chlorine concentration, electro-oxidative potential, pathogen contact time, and energy consumption. Optimal results were achieved with a pH of 4.6, electro-oxidative potential of 188 mV, active chlorine concentration of 3.4 mg/L, and a contact time of 1–2 min. The prototype produced 10.0 L of EW in 1 h, consuming 0.11 kWh of electricity. Real-scale energy consumption was 545 kWh/m3 EW, costing 12.51 euro/m3. The study concludes that optimizing EW production can reduce energy consumption, making it a viable alternative for industrial sanitization of fruits and vegetables.

Fabrication of graphitic carbon nitride/gum Arabic/potassium carrageenan composite for efficient adsorption of erythromycin: Kinetic and thermodynamic studies

Erythromycin (ERY) molecules are robust to the environment and hard to remove due to their aromatic structure. Nowadays, numerous researches have reported that the ERY amount in water is above the standard level and its removal is necessary. Here, we prepared three solid adsorbents: graphitic carbon nitride (g-C3N4), potassium carrageenan beads (Cr), and graphitic carbon nitride/gum Arabic/potassium carrageenan composite (g-ACr). Several techniques such as XRD, SEM, TEM, TGA, ATR-FTIR, Zeta potential, and N2 adsorption were employed to characterize the fabricated adsorbents. Five essential factors of adsorbent dose, initial ERY concentration, contact time, temperature, and pH were optimized to investigate the batch adsorption of ERY. The maximum adsorption capacity of 356.12 mg/g was attained by g-ACr composite at an adsorbent dose of 1.25 g/L, contact time of 6 h, and pH 7 at 15 °C. The data showed that the experimental findings exhibited the best agreement with Langmuir, Temkin, and DR isotherm models, in addition to the kinetic models of pseudo-second-order, Elovich, and intra-particle diffusion. The evaluated thermodynamic factors designated that the ERY adsorption is endothermic, physisorption, favorable, and spontaneous process. The g-ACr reusability displayed a decline in the adsorption capacity after seven adsorption/desorption runs by 5.7 %. Finally, this work outcomes depict that g-ACr composite is an efficient reusable adsorbent for ERY elimination from wastewater.

Threefold enhanced photodegradation of methylene blue using MgO composite with minimum Nd2O3: finding the sweet spot.

Removal of organic dyes like methylene blue (MB) from industrial effluents serves as potential source of potable water. Photocatalytic degradation using sustainable catalyst is deemed to be an affordable solution. In this work, Nd2O3/MgO nanocomposite with different compositions (1, 3, and 5wt% Nd2O3 with MgO) have been achieved using hydrothermal synthesis and characterized extensively. Interestingly, increasing Nd2O3 proportion (1-5%) enhances light absorption, and decreases band gap and electron-hole recombination. The efficacy of the photocatalysts is tested with the degradation of MB dye, through optimizing Nd2O3/MgO proportion, contact time, catalyst dose, and pH. Interestingly, control experiments reveal that 5wt% Nd2O3/MgO achieve 99.6% degradation of MB in 90min at pH 7, compared to 88.8% with bare MgO under same condition. Kinetic data show that 5wt% Nd2O3/MgO exhibits ca. 3 times higher degradation rate compared to MgO. For the first time, our work enable MgO-based sustainable photocatalyst development with minimum (5wt%) rare-earth combination to achieve excellent photocatalytic degradation performance.