Pseudo-first Order Kinetic Model Research Articles

ZnO/Zn3(PO4)2/CeO2 photocatalysts formed on zinc by plasma electrolytic oxidation

ZnO/Zn3(PO4)2 coatings doped with CeO2 particles for use in photocatalytic degradation of methyl orange (MO) were created by plasma electrolytic oxidation of zinc in a phosphate alkaline electrolyte (PAE) with CeO2 particle concentrations of up to 1.5 g/L. The CeO2 particle content in ZnO/Zn3(PO4)2 coatings was determined by the concentration of CeO2 particles in the PAE. Extensive research was conducted on coating morphology, chemical and phase compositions, and light-harvesting properties. The photocatalytic activity (PA) of ZnO/Zn3(PO4)2/CeO2 coatings was higher than ZnO/Zn3(PO4)2. The PA of ZnO/Zn3(PO4)2/CeO2 coatings strongly depends on the amount of CeO2 particles in PAE, and the highest PA was observed for ZnO/Zn3(PO4)2/CeO2 coating formed in PAE by adding 0.75 g/L of CeO2 particles. The higher PA of ZnO/Zn3(PO4)2/CeO2 compared to ZnO/Zn3(PO4)2 is due to a lower photogenerated electron/hole recombination. The photocatalytic degradation of MO followed a pseudo-first order kinetic model and the reaction constant of the most photoactive ZnO/Zn3(PO4)2/CeO2 coating was increased about twofold compared to the ZnO/Zn3(PO4)2 coating. After 6 hours of irradiation, the PA for ZnO/Zn3(PO4)2 and the most photocatalytically active ZnO/Zn3(PO4)2/CeO2 was about 70% and 98%, respectively. A mechanism for the photodegradation of MO with the ZnO/Zn3(PO4)2/CeO2 photocatalyst was also proposed.

Fe2O3/polypyrrole/peanut husk composite for the adsorptive removal of Basic Blue 41 from the aqueous medium: Kinetics, equilibrium modeling and thermodynamic studies

In this study, Basic Blue 41 (BB41) was adsorbed from an aqueous medium using a peanut husk (PH) functional composite with polypyrrole/Fe3O4. For the adsorption of BB41 dye, the effects of process variables including pH, sorbent dose, dye concentration, agitation time, and temperature were investigated. The magnetic composite showed the highest efficiency for the adsorbents at pH 7-10, 0.05 g adsorbent dose, 90 min contact time and 200 mg/L initial dye concentration at 27 °C. The qe was found up to 48 mg/g with percentage removal of up to 96% for BB41 dye for the composite. On the experimental data of BB41 dye, the Langmuir, Freundlich, Temkin, Harkin-Jura, and Dubinin-Radushkevich isotherms were applied. The BB41 adsorption data were also subjected to pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models. Thermodynamic factors, such as the change in enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°), were also calculated. The results show that the BB41 adsorption process is exothermic and spontaneous. Techniques such as FT-IR and scanning electron microscopy (SEM) were used to characterize the composite materials. This study demonstrated the promising adsorption potential of magnetic/polypyrrole/peanut husk composites. This class of adsorbent could be used to remediate wastewater that contains dyes.

Joint aerobic biodegradation of synthetic and natural textile microfibers and laundry surfactants

Microfibers (MFs) represent one of the most prominent sources of microplastics in aquatic environments, primarily released during textile washing alongside surfactants found in laundry detergents. This study aimed to investigate the biodegradability of natural (cotton) and synthetic (polyester) MFs individually and in combination with two surfactants: sodium lauryl sulfate (SLS, anionic) and polyoxyethylene glycerol ester (PGE-OE6, nonionic). Using the OECD 301 F test, the research assessed biodegradation patterns and environmental interactions. Biodegradation profiles have been fitted to a pseudo first-order kinetic model and to a logistic kinetic model. Results showed that cotton MFs were partially biodegradable, achieving a 74.9 % mineralization, while polyester MFs exhibited no biodegradability. Importantly, when combined with surfactants, the biodegradation of SLS was inhibited by polyester MFs, but cotton MFs enhanced SLS mineralization. Conversely, the combination of cotton MFs with PGE-OE6 slowed the biodegradation of both the surfactant and the MFs, delaying the onset of cotton degradation. However, polyester MFs’ biodegradability remained unaffected by either surfactant. These findings emphasize the need for more comprehensive assessments of how MFs and surfactants interact in real-world environmental matrices, as these interactions can influence their persistence and ecological impact. The study highlights the scientific importance of understanding pollutant interactions to develop more effective environmental monitoring and mitigation strategies.

In Situ Potentiometric Monitoring of Nitrate Removal from Aqueous Solution by Activated Carbon and Ion Exchange Resin.

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed.

In-depth mechanistic insights into Au nanoparticles based polyurethane foams as a selective and efficient dispersive solid phase microextractor for textile dyes from water: performance and reusability study

ABSTRACT Herein, a simple, superhydrophobic, superoleeophilic and low cost microextractor Au nanparticles (Au NPs) based polyurethane (PUFs) solid platform (Au NPs/PUFs) has been developed as a promising sorbent for removal and recovery of Congo red (CR) textile dye from water bodies. The sorbent was characterised using UV-visible and SEM techniques. The procedure relied complete dye retention from the aqueous solution at pH 5.0–5.5 onto an Au NP/PUF extractor. Analytical assessments revealed that the Au NPs/PUFs combination significantly improves mass transfer of dye and enhances creation of active sites for CR retention. CR sorption by the sorbent fitted well with intra-particle diffusion and pseudo first-order kinetic models (R2 = 0.990). The enthalpy change, ΔH (37.8 kJ mol−1) indicates that dye extraction is endothermic whereas the entropy change, ΔS0 (116.6 J mol−1K−1), reveals a significant change in the entropy during dye uptake. The free energy change ΔG (3.12 kJ mol−1 at 298 K) of CR sorption indicated that the dye retention was not spontaneous at all temperatures. A twofold sorption mechanism involving absorption accompanying ‘solvent extraction’ and/or ‘weak ion exchange’, combined with surface adsorption of dye is proposed. Sorbent packed mini column demonstrated effective percent removal and recovery (101.8%) of CR from water samples using acetone or NaOH as an eluting agent. The study expands the utility of Au NPs/PUFs for reusability and spectrophotometric sensing of trace levels of CR in water. The key attention also includes integrating PUFs utility by improving the selectivity and sensing properties towards textile dyes.

Electrochemical Degradation of Methylene Blue using Aluminum Doped Copper Oxide Electrode: Modeling and Optimization

An electrochemical oxidation process with an aluminum-doped copper oxide (Al@CuO) anode was modeled and optimized for the degradation of methylene blue (MB). The Al@CuO anode material was prepared by the thermal decomposition method. X-ray fluorescence (XRF) analysis confirmed the successful deposition of CuO on the aluminum substrate. The influence of current density, electrolysis time, and MB concentration on the performance of the electrochemical degradation of MB was modeled using Box-Behnken design (BBD). The accuracy of the proposed quadratic model by BBD was confirmed with a p-value < 0.0001 and adj-R2 > 0.9. The optimum MB degradation efficiency of 53.23 % was obtained at 80 mg MB concentration, 40 min electrolysis time, and 3.75 V applied current. The kinetics on the MB electrochemical degradation process using Al@CuO followed pseudo first-order kinetics model. These studies revealed that the Al@CuO anode electrode is not a promising anode for the electrochemical degradation of methylene blue.

Harnessing multifunctional antimony doped Tin (IV) sulfide nanosheets for chlorpyrifos degradation and hydrogen evolution

Multifunctional photocatalysts are vital for advancing environmental sustainability and clean energy. The hydrothermal method helped in optimized antimony (Sb) doping in the Tin (IV) sulfide (SnS2) lattice, increasing surface area with nanosheet assortment, as confirmed by Scanning Electron Microscopy and BET (Brunauer, Emmett and Teller) analysis. Moreover, the Fermi level shift towards conduction band within the semiconductor, increasing free electron concentration which enhanced conductivity and altered electronic properties. Photocatalysts were evaluated for Chlorpyrifos pesticide degradation, with studies conducted on photocatalytic parameters such as catalyst dosage, pesticide concentration, and pH to ascertain optimal degradation conditions. The 6 wt% Sb-doped SnS2 (6Sb:SnS2) demonstrated highest degradation efficiency within 60 min and degradation obeyed a pseudo first-order kinetic model with a rate constant of 0.0349 min−1. The degradation pathway of Chlorpyrifos and its transformation products was elucidated through High-Performance Liquid Chromatography-tandem mass spectroscopy. In addition, Sb doping empowers the surface traps and hydrophilicity of photocatalysts towards successful interaction between photogenerated electrons/holes with adsorbed oxidizable/reducible species. Moreover, 6Sb:SnS2 exhibited superior hydrogen evolution of 214.39 µmolg−1h−1, along with improved stability. Significantly, 6Sb:SnS2 attained Apparent Quantum Yield (AQY400 nm) of 39.49 % attributed to the doping induced band structure modification of SnS2 to match the hydrogen ion reduction potential.

Harnessing Moringa oleifera root powder (MORP) for the sustainable remediation of heavy metal contaminated water.

Heavy metal environmental pollution is rapidly increasing due to the increase in industrialization and urbanization. Industrial processes, such as paint production, mining, and raw materials producing industries release effluents rich in heavy metals, like Pb2+, Cd2+, Cu2+, and Cr3+. These heavy metals are dangerous because they persist in nature, are non-biodegradable and they have high tendency to accumulate in the environment and in living organisms who are exposed to them. This work studied the removal of heavy metals (Cu, Pb, Cr, and Cd) from aqueous solution using Moringa oleifera root powder (MORP) as the adsorbent. The MORP was characterized by SEM, FTIR, BET, and XRD. Batch adsorption experiments carried out investigated the effects of adsorbate concentration, adsorbent dosage, agitation time, pH and temperature on adsorption. The optimum parameters are: contact time (90 min); pH (9); adsorbent dose (0.6); metal ion concentration (30 mg L-1) for Cr and 40 mg L-1 for the rest; and temperature (50 °C) for Cu and Pb, and 70 °C for Cr and Cd. These experimental data were analyzed with 5 isotherm models (Temkin, Flory-Huggins, Langmuir, D-R and Freundlich). The result obtained fitted best to Temkin isotherm in comparison to others. Kinetic studies revealed that the pseudo-second order kinetic model best described the adsorption (with high R2 values ranging from 0.9810-0.9976) compared to pseudo-first order and intra-particle diffusion kinetics model. Results of the thermodynamic study showed that the sorption process was endothermic for Cu and Pb, but exothermic for Cd and Cr. The adsorbent showed good adsorptive tendencies toward the ions studied, and could be applied on an industrial scale for the remediation of metal contaminated water.

Photocatalytic Degradation of Mancozeb Pesticide Residue using Nanoceria Doped Zinc Oxide Nanoparticles under Natural Solar Irradiation

Introduction: Excessive applications of agrochemicals to meet the high food demand from ever-increasing populations are becoming a major issue for both health practitioners and environmental managers. Chemicals such as ethylene bis-dithiocarbamate pesticide mancozeb (MCZ) are known to have deleterious effects on the ecosystem. AIM: This study, aimed at assessing the suitability of cerium-doped zinc oxide (Ce-ZnO) for efficient degradation of MCZ fungicide. Method: The photocatalysts were synthesized using the coprecipitation method with zinc nitrate hexahydrate, cerium nitrate hexahydrate, and sodium hydroxide. The synthesized nanocomposites were further characterized by Powder X-ray Diffraction (PXRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDAX). The average crystallite size of the as-synthesized particles was found to be 31.42 nm, with very sharp PXRD peaks revealing the pure crystal nature of the particles. The photocatalytic degradation activity was evaluated following a series of experiments under natural environmental conditions. The optimal conditions for the degradation of MCZ fungicide using Ce-ZnO were found to be 10 ppm initial concentration of MCZ, 20 mg dose of the Ce- ZnO photocatalyst, 180 minutes irradiation time, and 10-11 atmospheric UV index. Result: At the optimum conditions, the degradation efficiency was found to be about 90% after 180 minutes. The reported photocatalytic degradation of MCZ using Ce-ZnO fits a pseudo-firstorder kinetic model with an R2 value of 0. 9677. Similarly, the reusability of the as-synthesized photocatalyst was evaluated and found to be active for five rounds with little change in the activity. Conclusion: Thus, the degradation method in the current study can be suitable for the degradation and removal of MCZ in agricultural runoff in the field.

KINETIC STUDY OF ESTERIFICATION CATALYZED WITH ALUMINUM SULFATE AIMED AT CONVERTING LEVULINIC ACID INTO METHYL LEVULINATE

Recycling lignocellulosic biomass is a sustainable alternative to the petrochemical industry since it allows the production of valuable, sustainable, and environmentally friendly chemical products, such as levulinic acid (LVA) and levulinate esters. Methyl levulinate (MLV), for example, has been assessed as a fuel additive with low toxicity, high lubricity, and flash point stability. In this respect, the present investigation details a kinetic study of methyl esterification catalyzed with aluminum sulfate aimed at converting levulinic acid into methyl levulinate. The reactions were carried out in a Parr Instruments stainless steel reactor to assess the effect of temperature (120, 140 and 160 °C) and reaction time (30, 60, 120 and 180 min) on LVA conversion into MLV, maintaining a constant LVA:methanol ratio of 1:8 and aluminum sulfate catalyst concentration of 0.04 mol.L-1. The maximum LVA-MLV conversion of 93.04 % was obtained at a temperature of 160 °C and reaction time of 60 minutes. The pseudo first-order kinetic model exhibited the best fit to the experimental data, with correlation coefficients (R²) greater than 0.96, and it was used to calculate activation energy, obtaining a value of 10.19 kcal.mol-1.

Boric Acid Removal from Water with Alginate Based Beads and Films as Adsorbents

High levels of boron cause harmful effects on humans, animals and plants. While boron is an important auxiliary nutrient for plants, excessive amounts cause toxic effects. The removal of boron in wastewater from chemical processes, industrial processes and agriculture is an important field of study. One of the most widely used methods for boron removal is adsorption method due to its low cost and ease of processing. In this study, adsorption method and sodium alginate microcapsules and sodium alginate-carbon nanotube film adsorbents were used as adsorbents for boric acid removal. In adsorption studies, sodium alginate-carbon nanotube film adsorbents with 42.11% boron removal were more efficient than sodium alginate microcapsules As a result of kinetic studies, it was found that the study was consistent with the pseudo-first order kinetic model.

Synthesis of gamma aluminum oxide nano-powder for adsorptive removal of nitrate from aqueous solutions

Nitrate pollution of surface and groundwater could be a worldwide issue resulting in the threat to the environment and public health. The removal of nitrate from water was carried out using gamma aluminum oxide (γ-Al2O3) nano powder. The nano powder was synthesized from aluminum oxide powder using the aqueous-based reflux method and applied for nitrate removal. The surface properties of the activated γ-Al2O3 were characterized using FTIR, XRD, and BET surface area analysis. Analysis of variance (ANOVA) was used to analyze nitrate removal to determine the appropriate regression model, which was found to be the quadratic model with a coefficient of determination (R2 = 0.99). The adsorption process was observed to be dependent on initial nitrate concentration, adsorbent dose, and time. The optimized nitrate removal efficiencies were 97.01% using a dose of 2.26 gL−1, an initial nitrate concentration of 10 mgL−1, and a contact time of 45 min. Additionally, the kinetics of nitrate ion adsorption was discussed based on pseudo-first order and pseudo-second order kinetic models. The experimental data fitted well with the pseudo-second order kinetic model, indicating that the adsorption mechanism is chemisorption. The equilibrium adsorption of nitrate experimental data followed the both Freundlich and Langmuir isotherm (R2 = 0.95), implying a homogeneous nature of the γ-Al2O3 surface sites. These results suggest further consideration of the practical application of γ-Al2O3 for nitrate treatment for domestic purposes.

Cu (II) adsorption in rice husk for water treatment: Batch and fixed column experiments

Cu (II) is a heavy metal found in water bodies and harmful to the environment and human health. Thus, this study evaluated Cu (II) adsorption in rice husk using batch and fixed bed tests, employing synthetic solutions and real water samples to simulate contaminated water treatment. Batch tests were performed using rice husk and synthetic Cu (II) solutions with concentrations varying from 1 to 128 mgL−1. The isothermal behavior of the adsorption process was evaluated using Langmuir and Freundlich nonlinear models, whereas mechanisms and adsorption rates were assessed using pseudo-first and pseudo-second order kinetic models. The fixed bed column was mounted on a 5-cm thick rice husk adsorbent bed and synthetic and real solutions were employed (concentration: 8 mg L−1; flux: 13 mL min−1). The equilibrium was reached after 20 min, with the best adjustment to the pseudo-second order model. The experimental data were better adjusted to the Langmuir model (estimated qmax: 7.19 mgg−1). The adsorption column exhibited adsorption capacities of 1.28 and 1.12 mgg−1 and saturation percentages of 83 % and 79 % for synthetic and real solutions, respectively, and were adjusted to Thomas model. The results indicate that rice husk can be an effective alternative for Cu (II) removal in contaminated water.

Removal of Pb(II) ions from aqueous solutions using natural and HDTMA-modified bentonite and kaolin clays

This work focused on the removal of Pb(II) from aqueous solution using kaolin and bentonite clays modified with hexadecyl trimethyl ammonium bromide (HDTMA). The clays were characterized using a zetasizer, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET), Fourier-transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Factors that influence the adsorption of Pb(II) from aqueous solution, namely pH, contact time, adsorbent mass, ionic strength, temperature and initial Pb(II) concentration were investigated. The results show that HDTMA was successfully incorporated into the kaolin and bentonite clay structures. The most favorable parameters for the adsorption of Pb(II) ions onto all adsorbents was pH of 6.0, temperature of 25 °C and adsorbent mass of 200 mg. Adsorption isotherms and kinetic studies showed that the adsorption of Pb(II) onto kaolin, bentonite and organobentonite clays followed the Langmuir isotherm and pseudo-first order kinetic model, while the adsorption onto organobentonite was better explained by the Freundlich isotherm and pseudo-second order kinetic model. Maximum monolayer adsorption capacity of organobentonite, calculated from the Langmuir model was 18.75 mg/g, which is higher than that obtained for the unmodified bentonite (14.71 mg/g); while for organokaolin it was 2.26 mg/g, which is less than that of the unmodified kaolin (4.19 mg/g). Thermodynamic studies showed that the reactions were exothermic and unfavoured at high temperatures. The adsorbents also showed good removal efficiency for up to four regeneration cycles.

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

Application of layered Nickel/Indium double hydroxide in the highly efficient removal of crystal violet dye from textile effluent

Worldwide freshwater demand will soon exceed supply if measures are not taken to mitigate inadequate wastewater treatment and its indiscriminate release into the environment. The textile industry is one of the largest consumers of freshwater and the third largest contributor to clean water pollution. Conventional treatment of textile effluent is inadequate and expensive. Adsorbent materials obtained from discarded solid waste precursors that contain high amounts of valuable metals can be an inexpensive way to obtain a highly efficient and low-cost wastewater treatment process. This study developed and explored a highly efficient adsorbent layered double hydroxide of Nickel and Indium (Ni/In-LDH) for the adsorption of widely used textile cationic dye, crystal violet (CV). The adsorbent material was synthesized by co-precipitation process of indium nitrate and nickel nitrate. The adsorbent material morphology and its adsorption capacity were investigated in different studies, such as the influence of pH, dosage, kinetics, isotherms, thermodynamics, ionic strength, adsorbent regeneration capacity, and interaction mechanisms of adsorption. Optimal operating conditions for Ni/In-LDH adsorption revealed maximum adsorption capacity Qmax of 570.94 mg g−1 at starting pH 8 and 60°C, which maintained approximately 75 % of the initial adsorption capacity in three successive adsorption/regeneration cycles. The experimental data fitted Pseudo first order kinetic model (PFO) and the Liu isothermal adsorption model. Thermodynamic studies indicated a spontaneous endothermic adsorption process, and a mechanism of physisorption of CV onto Ni/In-LDH substrate. After FTIR analysis of CV loaded Ni-In/LDH, electrostatic, hydrogen bonding, and n-π bonding interactions were suggested as the interaction mechanisms of adsorption. The Ni/In-LDH demonstrated excellent performance in the removal of CV dye in aqueous solutions compared to other high performing adsorbents.

KINETIC, ISOTHERM AND THERMODYNAMIC STUDIES OF THE ADSORPTION OF CRESOL RED DYE USING AGRICULTURAL WASTES

Agricultural wastes and plant biomass are alternative low-cost adsorbents because they can be used without or with a minimum processing. In the present study, batch experiments were carried out to study the adsorption of cresol red (CR) unto mango leaf (ML) and orange peel (OP). Several parameters that affect adsorption process such as pH, adsorbent dosage, contact time, initial dye concentration and temperature were investigated. FTIR and SEM were used to determine the functional group responsible for adsorption. The results revealed that the highest adsorption efficiency was at pH 5 for the two adsorbents. It was also discovered that CR removal efficiency increased with the increase in contact time and adsorbent dosage while adsorption capacity was higher with increase in initial dye concentration but removal efficiency was lowered. The kinetics conform with the pseudofirst-order kinetic model for mango leaf but conform with the pseudo-second-order kinetic for orange mesocarp due to the value of the correlation coefficient (R2). Based on the value of correlation coefficient, the experimental results for the removal by mango leaf best fitted the Langmuir isotherm model with monolayer adsorption capacity of 70.64 mg. g-1, while Freundlich isotherm model was best fitted to the experimental results for the adsorption of CR by Orange peel. The thermodynamic results revealed that the process is spontaneous and endothermic.

Removal of hazardous Aniline Blue dye using a potential Biosorbent – Hen feather

In this research we have successfully removed a highly toxic dye, “Aniline Blue”, from its aqueous solution employing an adsorbent, Hen Feathers. The dye adsorption over Hen Feather was comprehensively studied over ranges of contact time, pH, concentration, and adsorbent dosage, and the optimum values were evaluated. In order to understand the behaviour of the adsorption system, various isotherm models were evaluated at temperatures of 30, 40 and 50 °C. The data obtained from contact time studies were used to test pseudo-first and pseudo-second order kinetic models and it was found that the adsorption follows pseudo-second-order kinetics. Using the Langmuir constant, b, thermodynamic parameters including ΔG°, ΔH° and ΔS° were calculated and it was ascertained that the process is endothermic (positive ΔH°), involves an increase in disorder (positive ΔS°) and is spontaneous (negative ΔG°). The values of the separation factor (r) also confirmed a favourable adsorption process at all three temperatures studied. Overall, it is affirmed that the adsorbent, Hen Feather, acts as highly potent scavenger to remove the dye Aniline Blue from its aqueous solutions.

Adsorption of reactive blue day 49 from aqueous solution on commercial activated carbon and polyaniline electrochemically deposited on carbon felt: Kinetic modeling and equilibrium isotherm analysis

In this study, we investigated the effectiveness of commercially available activated carbon (CAC) and carbon felt (PANI/CF) for the removal of reactive blue dye 49 (RB49) from an aqueous solution. We performed a parametric analytical adsorption research in order to achieve this goal, looking at the impact of several important parameters like the adsorbent mass, the absorption duration, the concentration of ionic strength, and the pH of the RB49 solution. The measurement results demonstrate that the CAC dosage ranged from 0.1 to 5 g. The adsorption levels of RB49 increased from 17.73 % to 97.62 % and the PANI/CF assay from 0.228 to 1.044 g. The percentage of delayed adsorption of RB49 increased from 90.78 % to 99.97 %. It was found that the highest RB49 adsorption was obtained from pH < 7 for both adsorbents. The RB49 adsorption yield increased and then stabilized at equilibrium within 2 hours of contact. The kinetics of RB49 adsorption were determined using pseudo-first-order, pseudo-second-order and Elovich models. According to the experimental results, the pseudo-first order kinetic model proved to be the most suitable for the CAC adsorbent, while the three kinetic models were perfectly suitable for the PANI/CF adsorbent. The adsorption (parameters) isotherms of RB49 were studied using the Langmuir, Freundlich and Temkin models. The experimental data are more satisfactory and better fitted to the Langmuir model for the adsorption of RB49 on CAC and the second adsorbent CF/PANI; the results show that the adsorption studied is in agreement with the three isothermal models. The study shown that the organic dye RB49 may be successfully removed from aqueous solutions using CAC and PANI/CF as adsorbent materials.

Recovering ammonium from real treated wastewater by zeolite packed columns: The effect of flow rate and particle diameter

Nitrogen (N) recovery from wastewater is a desirable way to create a (N) neutral society in view of a circular economy approach. Nitrogen recovery from wastewater by employing adsorption columns filled with zeolite can be a very attractive solution. This study assessed the effect of influent flow rates (namely, 1.6 and 2.3 L h−1) and particle diameters (namely, 0.5–1.0 and 2.0–5.0 mm) of zeolite packed in columns on recovering NH4+ from real domestic treated wastewater (RDTWW). Findings revealed that maximum NH4+ recovery can be achieved by using zeolite with the smallest particle diameter (0.5–1.0 mm) and the highest influent flow rate (2.3 L h-1). The maximum NH4+ adsorption rate was 1.2, 21 and 9.8 mg NH4+ kg-1 h-1 after 205, 32 and 35 h of operation. NH4+ adsorption data were analysed by fitting them to both pseudo-first and pseudo-second order kinetic models. The former model best approximated NH4+ adsorption data. Such a result suggested that the amount of NH4+ adsorbed depended solely on the amount of NH4+ in contact with the zeolite surface. Results successfully established the application of zeolite-packed columns in removing NH4+ from real domestic treated wastewater and the effects of process parameters.