Langmuir Isotherm Research Articles

A sustainable approach for the corrosion control of mild steel using Cocous nucifera gum: An electrochemical investigation

The study of corrosion inhibition on mild steel (MS) in an acid medium (1 M HCl) solution was performed using a crude extract of Cocousnucifera gum (CNG). Cocousnucifera develops gum exudates on its palm, the exudate process occurs mainly after some physical or microbiological injuries and is formed on the fruit of the palm. The gum was utilized to study the corrosion inhibition of MS by electrochemical and surface studies. The characterization of the crude gum was done by Fourier transform infrared spectroscopy (FT-IR) which revealed the presence of several active components (aromatic and oxygen-containing functional groups) in its structure. The electrochemical studies resulted in the maximum inhibition efficiency value of 75.64 % at the highest inhibitor concentration of 4000 ppm at 308 K. It was inferred that both the anodic dissolution of the metal and cathodic hydrogen evolution were effectively decreased in the presence of Cocous nucifera gum extract, revealing that inhibitor is of mixed type. From the adsorption studies, it was found that the best fit with R2 ∼ 0.9 followed Langmuir adsorption isotherm indicating the monolayer adsorption of the inhibitor on the metal surface. Gibb’s free energy of adsorption values was found <−20 kJ/mol, a characteristic of predominant physical adsorption. To support the electrochemical data SEM (scanning electron microscopy), AFM (Atomic force microscopy), and X-ray diffraction analysis were performed and these are in good agreement.

Synthesis and characterization of novel magnetic metal organic framework for efficient removal of ketoprofen from aqueous solutions: Mechanism of interaction, adsorption and optimization via BOX-Behnken design

This investigation examines the adsorption and elimination of the anti-inflammatory medication ketoprofen (KTP) in relation to a newly developed magnetic thorium metal-organic framework (MTh-MOF). The study found that KTP absorption on MTh-MOF resulted in a reduction in pore volume, pore size, and surface area, as revealed by N2 adsorption/desorption isotherm analysis used to evaluate the characteristics of the MTh-MOF. Scanning electron microscopy (SEM) showed that the pore radius of MTh-MOF decreased from 1.68 nm to 0.82 nm, demonstrating a consistent and uniform structure. Fourier-transform infrared (FT-IR) spectroscopy was employed to identify the functional groups present in MTh-MOF, while X-ray photoelectron spectroscopy (XPS) was used to confirm the compound's structure. The optimal conditions for achieving a high adsorption capacity were found to be at pH 6 and a MTh-MOF dose of 0.02 g. The results indicated that MTh-MOF displayed a high capacity for absorbing KTP, with the adsorption data fitting well with pseudo-second-order kinetic models and the Langmuir isotherm. The adsorption capacity of MTh-MOF for KTP was determined to be 518 mg/g. The adsorption energy of 28.26 kJ·mol–1 suggested that chemisorption was the predominant mode of adsorption. The process of KTP adsorption on MTh-MOF was observed to be spontaneous, endothermic, and random, as evidenced by the temperature-dependent increases in the thermodynamic parameters (ΔGo, ΔHo, and ΔSo). The adsorption process was optimized using Response Surface Methodology and Box-Behnken design (RSM, BBD). Aromatic rings interact via π-π bonding, while chemisorption involves the development of chemical interactions between the adsorbate and adsorbent. Additionally, electrostatic interactions arise from the attraction or repulsion of charges between the adsorbate and adsorbent, and pore-filling occurs when the adsorbate fills the adsorbent's pores. In order to understand the electrical properties, reactivity, and shape of KTP, density functional theory (DFT) was utilized.

UiO-66 MOF/Zr-di-terephthalate/cellulose hybrid composite synthesized via sol-gel approach for the efficient removal of methylene blue dye.

This research addresses the issue of organic dye pollution in water by developing eco-friendly, cost-effective adsorbents. Zr-di-terephthalate organic-inorganic hybrid materials, with and without cellulose, were synthesized using a one-pot sol-gel method with zirconium butoxide and terephthalic acid. The materials were characterized by XRD, FTIR, XPS, SEM, EDS, TEM, and BET analysis and showed a crystalline structure with some amorphous content, high surface area, and small pores, indicative of a composite form containing UiO-66 metal-organic frameworks (MOFs). Adsorption studies on methylene blue dye showed that both materials followed Langmuir isotherms, with maximum adsorption capacities of 147.54 mg/g for Zr-(TPA)2-U and 151.38 mg/g for Zr-(TPA)2-UC. The materials exhibited rapid adsorption within a short period of 30 min and adhered to pseudo-second order kinetics. The adsorption process was spontaneous and endothermic, driven by electrostatic interactions, π-π stacking, pore filling, van der Waals forces, and hydrogen bonding. The fact that the composite materials contain the UiO-66 structure contributed to their effective adsorption by increasing the crystalline properties of the material. The hybrids also showed excellent reusability, maintaining high efficiency over multiple cycles. These findings highlight the potential of Zr-di-terephthalate hybrids as sustainable, high-performance adsorbents for water purification, addressing dye contamination effectively.

Adsorption characteristics and mechanism of novel ink melanin composite modified chitosan for Cd(II) in water

In this study, chitosan (CS), carboxymethyl chitosan (CMCS), and chitosan quaternary ammonium salt (HACC) were successfully loaded with ink melanin (ME) as efficient adsorbents for Cd(II) removal. The results of batch adsorption experiments and structural characterization showed that the modified CS loaded with ME improved the adsorption capacity of the composites for Cd(II). The pseudo-second-order kinetic and Langmuir equations were better suited to describe the batch adsorption experiments. The adsorption of Cd(II) was chemisorption with desirable adsorption effect when the concentration of the three composites was 0.5 mg/mL and the pH value was neutral. Among them, HACC-ME demonstrated remarkable Cd(II) adsorption performance (107.18 mg/g) and sustained an 85 % efficiency in Cd(II) removal over five adsorption-desorption cycles. Ion exchange, complexation, electrostatic attraction, and hydrophobic interaction were the primary mechanisms for Cd(II) removal. Overall, HACC-ME could be employed as a low-cost and highly efficient new natural adsorbent material for the removal of Cd(II) ions from wastewater. These findings illuminate pathways for the development of efficient and novel natural adsorbent materials for environmental cleanup purposes.

Waste biomass-based graphene oxide decorated with ternary metal oxide (MnO-NiO-ZnO) composite for adsorption of methylene blue dye

In this study, a novel approach for the removal of methylene blue (MB) dye is effectively illustrated by using biomass based composite adsorbent. The investigation employed areca nut husk (AH) to produce graphene oxide (GO) by a single step calcination method. Thereafter, AH-GO was incorporated by using ternary metal oxide (TMO) via hydrothermal treatment. The developed AH-GO@MnO-NiO-ZnO composite was characterized by various analytical techniques, including FT-IR, XRD, FESEM, HRTEM, BET surface area and Raman spectroscopy which exhibited promising properties for dye adsorption. To study the adsorption efficiency of prepared composite, optimization experiments were performed for adsorbent dose, initial dye concentration and contact time. The optimized parameters during adsorption phenomenon were found to be 0.5g/L of dose, 20mg/L of initial concentration and 180min of time exhibiting removal efficacy of 93.05 ± 0.93%. Moreover, adsorption isotherm and kinetic models were analysed to explore the adsorption behaviour of AH-GO@MnO-NiO-ZnO towards MB dye. The adsorption isotherm and kinetic studies followed Langmuir isotherm model and pseudo-second-order (PSO) model respectively. AH-GO@MnO-NiO-ZnO has demonstrated a maximum adsorption capability of 127.06mg/g. These findings collectively underscore the potential of AH-based adsorbent as a viable, inexpensive, and environment friendly for the treatment of wastewater contaminated with MB dye.

Adsorption and removal of Pb (II) via layer double hydroxide encapsulated with chitosan; synthesis, characterization adsorption isotherms, kinetics, thermodynamics, & optimization via Box-Behnken design

The study aimed to enhance the stability and efficiency of removing bivalent Pb(II) by encapsulating AlNi-layered double hydroxide (LDH) in chitosan and itaconic acid to create an adsorbent with chemically active sites. The resulting material, AlNi-LDH/CS, underwent thorough property analysis using XRD, FT-IR, XPS, EDX, N2 adsorption/desorption isotherm, and FESEM to find out what textural characteristics it has. Specifically, nitrogen adsorption/desorption isotherms were utilized to assess the textural properties of AlNi-LDH/CS. The Al/Ni-LDH/CS surface displayed a specific surface area of 71.95 m2/g and an average pore size of 2.537 nm, consistent with the platelets' external surface. The effects of dose, pH, temperature, and starting concentration on the adsorption process were also investigated in this study. The adsorption characteristics have been examined by means of equilibrium and adsorption kinetics. The adsorption process adhered to the pseudo-second-order and Langmuir isotherm models. The predominant adsorption process was found to be chemisorption, which had an adsorption energy of 28.42 kJ·mol−1. An endothermic and spontaneous adsorption process is suggested by the increase in metal absorption at increasing temperatures. The Box-Behnken design software was utilized to establish the optimal adsorption parameters as pH 5, a dosage of 0.2 g of AlNi-LDH/CS per 25 mL, and an adsorption capacity of 453.05 mg/g for the Pb(II) arsenate solution. For the composite sponge to be most effective in adsorbing arsenate and be used in water purification procedures, these factors are essential. The adsorption process was successfully improved with few planned tests by applying the Box-Behnken design and response surface technique aspects of the Design-Expert software. An evaluation of the adsorbent's reusability using six successive cycles of adsorption and desorption confirmed its stability and showed no discernible decrease in removal efficiency. Additionally, it retained its original chemical composition before and after reuse, showcased consistent efficiency, and maintained uniform XRD data.

Selective adsorption of arsenic by water treatment residuals cross-linked chitosan in co-existing oxyanions competition system

Selective adsorption of arsenic in co-existing oxyanions competition systems remains a significant challenge in water treatment due to the limitations of adsorbent materials that often overlook competitive adsorption, resulting in an overestimation of their actual purification potential for target contaminants. In this study, a novel hydrogel bead adsorbent, composed of water treatment residuals (WTRs) and chitosan (Chi), was developed to selectively remove arsenic, while minimizing the interference from phosphate, which is the strongest and most representative competitor in multi-oxyanion systems. The WTRs-Chi beads (WCB) adsorbents were optimized by adjusting the ratios of WTRs:Chi, with characterization results indicating that increased WTR doping improved the degree of crosslinking and the formation of bidentate complexes with enhanced electrostatic selectivity. Importantly, the co-existence of phosphate had minimal adverse effects on arsenic removal compared to other reported adsorbents. The maximum adsorption capacity for As (Ⅴ) in the binary system was 34.12 mg/g, and the adsorption behavior was fitted well by the pseudo-second-order kinetic model and the extended Langmuir isotherm model. The experimental results, supported by X-ray photoelectron spectroscopy analysis (XPS), revealed that both As (Ⅴ) and P (Ⅴ) adsorption in the single system were driven by electrostatic attraction and ligand exchange. However, in the binary system, the inhibition of P (V) adsorption was attributed to competitive desorption caused by electrostatic repulsion, which hindered the formation of inner-sphere complexes. This study provides a practical approach for developing selective adsorbents to address arsenic contamination in complex water environments and promotes the recycling of municipal solid waste.

Quantitative mechanisms for the Cd2+ adsorption increased by sewage-sludge biochar but decreased by rice-straw biochar after melamine modification

To explore the relative contributions of different mechanisms to Cd2+ adsorption by melamine (C3H6N6) modified biochars, the adsorption characteristic experiments including adsorption kinetics, isotherms and thermodynamics were performed, and the qualitative and quantitative characterization of adsorption mechanisms were further analyzed by SEM-EDS, XRD, FTIR, XPS and the calculation, respectively. When initial pH increased from 1.0 to 7.0, the adsorption capacities were increased, and began to decline after reaching maximum capacities at pH of 5.0 for both modified biochars. After C3H6N6-modification, the maximum adsorption capacity of sewage-sludge biochar (SSB) increased from 64.20 to 126.75 mg/g, but the maximum capacity of rice-straw biochar (RSB) decreased from 52.03 to 25.65 mg/g. For both pristine biochars, the adsorption process was better described by pseudo-second-order kinetic and Langmuir isotherm models, whereas it did not change the applicability of the adsorption models after modification. The thermodynamics confirmed that all the adsorptions were endothermic process under different temperatures of 293, 303 and 313 K, suggesting higher temperature was more conducive to the adsorption. Such an enhancement was supported by more aromatic structure in modified SSB (N-SSB) compared to SSB, which was qualitatively confirmed by FTIR and XPS observation, and the enhancement was fundamentally caused by the increases in the importance of Cπ-coordination mechanism, accounting for 20.30 % (SSB) to 41.12 % (N-SSB) of total adsorption. While for modified RSB (N-RSB), the reduction was primarily explained by the decreased contribution of cation-exchange mechanism to total adsorption, since the contribution proportion was reduced from 80.16 % to 55.65 % after modification. The present analyses would shed light on the mechanisms underlying the adsorption by similar modified adsorbents, and the application of rice-straw biochar by C3H6N6-modification for the Cd2+ adsorption should be investigated prudently in future.

Removal of Pb(II), Cr(III), Co(II), Cu(II) cations from aqueous solutions using tetraethylenepentamine-functionalized HY cubic zeolite: optimization, characterization, and mechanistic insights.

This research utilized tetraethylenepentamine-functionalized HY cubic zeolite as an adsorbent to effectively remove heavy metals from aqueous solutions. The adsorbent was characterized using FT-IR, XRD, TGA, FE-SEM, and EDS-MAP techniques. The synthesis aimed to optimize and evaluate the removal efficiency of Pb(II), Cr(III), Co(II), and Cu(II) from aqueous solutions by investigating key parameters, including initial pH, concentration, adsorbent dosage, and contact time. The results indicate that the highest adsorption capacities for each metal follow the order: Pb(II) > Cr(III) > Co(II) > Cu(II), with respective percentages of 99.7%, 98.2%, 95.1%, and 92.4%. Analysis of the batch systems reveals that the equilibrium data for Pb(II), Cr(III), Co(II), and Cu(II) align well with the Langmuir and Freundlich isotherms also show a good fit, with correlation coefficients (R2) higher than 0.9335 and 0.9478, respectively. The maximum adsorption capacities (181.82, 175.44, 169.49, and 158.73mg/g) reflect the nature of the adsorption process. Kinetic studies for Pb(II), Cr(III), Cu(II), and Cu(II) yielded correlation coefficients (R2) higher than 0.9971. These high R2 values suggest that the experimental data closely fit a pseudo-second-order model, indicating a two-step adsorption mechanism. Heavy metal removal is attributed to ion exchange and chemisorption within the zeolite pores, involving interactions with nitrogen lone pairs.

Optimisation of mercury adsorption by ZIF-8 from aqueous solutions through response surface methodology

ABSTRACT Mercury is one of the most toxic heavy metals. Various techniques have been used to remove it from water sources. Among these, adsorption is a low-cost and effective method to remove mercury even in very low concentrations. One of the adsorbents that has gained considerable popularity recently is the zeolite imidazolate framework-8 (ZIF-8). In this study, after the synthesis of ZIF-8, its properties were determined using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission electron microscopy (FESEM). Temperature (25–61 °C), contact time (5–85 min), adsorbent dosage (0.1–0.9 g/L), pH (2–10), and initial mercury concentration (24- mg/L) were investigated. The optimal conditions for the adsorption method were determined using the response surface methodology (RSM). The optimal conditions for mercury elimination included a primary mercury concentration of 4 mg/L, a temperature of 61°C, adsorbent dose (0.5 g/L), and a pH of 7; the elimination efficiency under these conditions was 91.66%. The adsorption equilibrium data were analysed using Langmuir and Freundlich isotherm models, and the Langmuir model was found to be consistent with the adsorption isotherm (R2 = 0.9363). The adsorption kinetics closely matched the pseudo-second-order model (R2 = 0.9998). These results indicate that the nanoporous adsorbent ZIF-8 can successfully eliminate mercury from aqueous environments.

Electrochemical study and modeling of an innovative pyrazole carboxamide derivative as an inhibitor for carbon steel corrosion in acidic environment.

The impact of N,1-dibenzyl-5-methyl-1H-pyrazol-3-carboxamide (BPC) on the carbon steel (CS) corrosion in hydrochloric acid (1M) was studied in this work, considering concentration and temperature effects. Electrochemical investigation indicated that BPC functions as a mixed-type inhibitor. For an optimal BPC concentration of 125ppm, the inhibition efficiency of 91.55% was obtained at 298K. According to adsorption isotherm of Langmuir, the BPC adheres to the CS with standard adsorption free energy (ΔG°ads) of - 26.76kJmol-1. Furthermore, the calculation of dissolution activation parameters revealed an increase in energy (Ea) from 46.48 to 94.97kJmol-1, an elevation in the enthalpy (∆Ha) from 43.89 to 92.37kJmol-1, and a rise in the entropy (∆Sa) from - 91.17 to 51.43Jmol-1K-1 in the presence of 125ppm of BPC. The experimental results were confirmed by quantum chemistry calculations based on density functional theory (DFT) and molecular simulations using the Monte Carlo method. These theoretical approaches also allowed for a comparison of the inhibitory performances of BPC with its protonated form, BPCH, the latter being found more effective. Moreover, the study of the radial distribution function g(r) predicted that the nature of the bond formed with the steel surface is of a chemical type.

Crop-Derived Biochar for Removal of Alachlor from Water

The presence of various pesticides in natural streams and wastewater is a significant environmental issue due to their high toxicity, which causes harmful consequences even at low quantities. One cost-effective method to remove these pollutants from water could be through adsorption using an inexpensive, easily obtained adsorbent—biochar. The presented research demonstrates the efficacy of applying biochar obtained from wheat grains to eliminate alachlor from water. The sorption properties of the biochar and the likely removal mechanisms are defined. The study found that the biochar removed 76–94% of alachlor, depending on the initial concentration of the pesticide in water. The maximum removal of alachlor (94%) using biochar occurred at an initial pesticide content of 1 mg/L. Both the pseudo-second-order kinetic (R2 = 0.999) and the Langmuir isotherm models (R2 = 0.996) effectively characterized the elimination of alachlor by wheat grain biochar. The biochar’s maximum adsorption capacity for alachlor was 1.94 mg/g. The analyzed biochar, with its micropores and various surface functional groups, was able to effectively adsorb alachlor and trap it within its structure.

Functional ZnONPs-modified biochar derived from Funtumia elastica husk as an efficient adsorbent for the removal of sulfamethoxazole from wastewater.

Funtumia elastica husk was employed as an efficient and economically viable adsorbent to supplement traditional treatment methods in the removal of sulfamethoxazole from wastewater by converting it into usable material. The purpose of this study was to make biochar (FHB) from Funtumia elastica husk through the pyrolysis process and further modify the biochar using zinc oxide nanoparticles (ZnONPs) to a nanocomposite (FBZC). The antioxidant and antimicrobial characteristics as well as the potential of FBZC and FHB to sequester sulfamethoxazole from wastewater were investigated. Uptake capacities of 59.34mgg-1 and 26.18mgg-1 were attained for the monolayer adsorption of SMX onto FBZC and FHB, respectively. SEM and FTIR spectroscopic techniques were used to determine the surface morphology and chemical moieties of adsorbents, respectively. Brunauer-Emmett-teller (BET) surface analysis was used to assess the specific surface area of FHB (0.5643 m2g-1) and FBZC (1.2267 m2g-1). The Elovich and pseudo-first-order models are both well-fitted by the experimental data for FHB and FBZC, according to kinetic results. Nonetheless, the equilibrium data for FHB and FBZC were better explained by the Freundlich and Langmuir isotherm models, respectively. The pHPZC values of 6.83 and 5.57 were determined for FBZC and FHB respectively. Optimum solution pH, dosage, and contact time of 6, 0.05g, and 120min were estimated for FHB and FBZC. In conclusion, these findings demonstrate the strong potential of FBZC to simultaneously arrest the spread of pathogenic microbes and sequester sulfamethoxazole from wastewater.

Evaluation of mycotoxin binders against deoxynivalenol and fumonisin B1 using isotherm models and linear equations

This study was conducted to evaluate the adsorbent characteristics of two mycotoxin binders (BBAc – composed of bentonite, β-glucans, and activated charcoal, and SepHt – composed of heat-treated sepiolite) against deoxynivalenol (DON) and fumonisin B1 (FB1) using Brunaeur-Emmett-Teller, Dubinin–Radushkevich, Freundlich, and Langmuir isotherm models and linear regression equations. Both products were tested in vitro at 0.5% with increasing levels of DON or FB1 (0.5–10 mg L−1) using solutions of pH 3 and pH 6 and analysed by LC-MS/MS. FB1 adsorption rates were not different between the products (p > 0.05) at pH 3 and pH 6. At a DON concentration of 1 mg L−1, BBAc had higher (p < 0.05) adsorption rates than SepHt. For DON, the Freundlich model had the best fit with BBAc at pH 3 and 6, and the Langmuir model with SepHt at both pHs. For FB1, the Freundlich model had the best fit with BBAc and SepHt at pH 3, and the Langmuir model with both products at pH 6. All the linear regression equations had lower R2 than the isotherm models. Therefore, the adsorption isotherm models provided more informative and reliable data for the mycotoxins and mycotoxin binders tested herein.

Improved Adsorption of Organic Dyes onto a Polypyrrole/Tannic Acid Nanocomposite.

Methyl orange (MO) and methylene blue (MB) dyes are toxic and carcinogenic; thus, their presence in water bodies has been a major concern. Designing an efficient adsorbent for removal of these dyes is a scientific challenge for researchers. In this work, a polypyrrole-tannic acid nanocomposite was prepared via a chemical oxidation method and used as a novel adsorbent for removing these toxic dyes. The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller methods. The effect of different parameters on adsorption such as adsorbent doses, temperature, pH, initial dye concentration, and contact time was studied. The adsorption was in line with pseudo-second-order kinetics and the Langmuir isotherm model. ΔG°, ΔH°, and ΔS° were calculated to ascertain the feasibility of adsorption. The maximum adsorption capacities attained for this adsorbent were found to be 204.08 mg/g toward the MO dye and 217.39 mg/g toward the MB dye.

Investigating the adsorption potential of coconut coir as an economical adsorbent for decontamination of lanthanum ion from aqueous solution

Coconut coir was explored as economical sorbent for the adsorptive removal of lanthanum ion (La3+) from aqueous media. Both column and batch studies were conducted to assess the effective removal of La3+ on coconut coir by optimizing different adsorption variables such as bed height, flow rate, pH, adsorbent dosage, shaking time, initial metal concentration, and temperature. Characterization of coconut coir was carried out by scanning electron microscopy (SEM), FT-IR, and BET studies prior and subsequent to adsorption. The effective removal of La3+ was defined in certain media by the pHzpc, which was found to be 5.7 ± 0.1. The optimum 94.04 ± 0.2% adsorption of La3+ on coconut coir was observed by shaking 4 cm3 of 90 mol/L solution of La3+ with 0.3 g adsorbent dose for 10 min at neutral pH. The Langmuir adsorption capacity was found to be q e = 2.88 ± 0.02 mg g − 1 and Freundlich adsorption capacity was KF = 0.1294 ± 0.03 mg g − 1 . The pseudo-second-order kinetic and Langmuir isotherm models provided an ideal fit for the adsorption process. The column analysis also showed direct correlation of bed height and initial metal concentration with % adsorption, while % removal decreased as flow rate increased. The high regression coefficient values confirm that the BDST model is in line with the test data. Van’t Hoff equation proved the spontaneous endothermic process. Effect of external ions and desorption are also studied. The results suggest that coconut coir is a cost effective and efficient bio-sorbent for La3+ ion adsorption from aqueous solution.

Synthesis of calcium phosphate nanomaterial from quail eggshell for cadmium removal from wastewater and its genotoxic/cytotoxic properties.

In recent years, pollutants released into the environment from various sources threaten environmental health. Rapid industrialization and the constantly increasing needs of people facilitate the release of more hazardous wastes into the ecosystem. The presence of pollutants in water resources causes a wide range of adverse effects. In this study, calcium phosphate nanomaterial (Ca3(PO4)2 NM) was synthesized from biological waste eggshells for the cadmium removal in synthetic domestic wastewater, and a treatment method was developed using these NMs. The Ca3(PO4)2 NMs were produced by using a biowaste which provides the synthesis procedure greener approach. The biogenic NMs were used to remove toxic cadmium ions from wastewater samples. Cytotoxicity and genotoxicity studies of the synthesized NMs were also carried out, and their possible effects on the health of living organisms and the ecology were examined. In the developed method, the parameters affecting the removal of cadmium from wastewater samples were optimized and the removal efficiency was calculated by determining cadmium in a flame atomic absorption spectrophotometer system (FAAS). Synthetic domestic wastewater samples were utilized for evaluating the applicability of the developed treatment strategy. In addition, the adsorption capacity of the material for Cd2+ ion was calculated and the values obtained were modeled by using Langmuir adsorption isotherm (LAI). The calculated LAI parameters were within the appropriate limits, which proved that the developed NM can be used as an effective material for cadmium removal. Moreover, a new, rapid, and feasible synthesis strategy for the synthesis of Ca3(PO4)2 NM was presented in the literature.

Eco-friendly impact of a novel green Melilotus officinalis extract as a sustainable inhibitor to reduce acid corrosion of copper.

In this study, we deployed green Melilotus officinalis extract (MOE) as a corrosion inhibitor for copper. The anticorrosion properties of MOE for Cu in 1 M HNO3 were investigated by various experimental and numerical techniques, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and a weight loss (WL) method at different temperatures. Additionally, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX) and atomic force microscopy (AFM) were utilized to examine the surface morphology of Cu with and without the extract. By contrasting the inhibition effectiveness with and without the extract, the inhibition efficiency (% IE) was observed. The WL method revealed that 300 ppm of the extract had an IE of 93.8% for Cu immersed in one molar HNO3 solution. The MOE was classified as a mixed type according to the PDP study since it delayed both cathodic and anodic processes, with a cathodic predominance. At 25-45 °C, MOE's free adsorption energies were 23.1-21.5 kJ mol-1, showing that mixed-type adsorption occurred on the Cu surface. Additionally, the Langmuir adsorption isotherm and the adsorption data from the WL tests of MOE showed a good match. The extract could adsorb spontaneously onto the metal surface, according to the thermodynamic conditions. Analysis of the corrosion product using different techniques revealed that a protective layer had formed on the metal's surface. Hence, MOE had a good corrosive inhibitive effect on Cu in HNO3 solution. It turned out that all the methods used gave consistent results.

Sustainable Bio‐Adsorbents From Banana Post‐Harvest Agricultural Residues: Kinetics, Equilibrium, and Mechanism Prospection of Methylene Blue Dye Adsorption

ABSTRACTWater pollution from industrial‐colored effluents, generated by large volumes of liquid effluents containing synthetic dyes, generally harmful and non‐biodegradable, affects environmental biota and human health. Considering the potential use as bio‐adsorbents of agro‐industrial residues, in the present work insights into the kinetics, equilibrium, and mechanism of the methylene blue (MB) dye adsorption by six bio‐adsorbents produced from the post‐harvest residues from the banana tree, a widely cultivated crop in Brazil, were investigated. The six prepared bio‐adsorbents were tested to verify the adsorption capacity as gross residues, after carbonization, and after alkaline‐chemical activation. Bench‐scale experiments conducted at different conditions showed that experimental data were better described by the Langmuir isotherm, by the intraparticle diffusion model (with external diffusion being the dominant step), followed by the pseudo‐second‐order model, indicating the predominance of monolayer chemisorption. In addition, maximum adsorption capacities ranged between 10.55 and 25.51 mg/g, with a higher dye removal rate at alkaline pH. The adsorption of the MB dye onto the six produced bio‐adsorbents occurred through both polar and nonpolar interactions. The overall study indicated that both the pseudo‐stem and the leaves from post‐harvest banana crops could be a cost‐effective natural bioresource for producing efficient and sustainable bio‐adsorbents for treating colored liquid effluents.

Engineered Mg-modified biochar-based sorbent for arsenic separation and pre-concentration

The utilization of biochar as a relatively efficient sorbent or stationary phase for the separation and preconcentration of a wide range of analytes represents an innovative approach in current sample pretreatment methods. Appropriate pre- and post-pyrolysis modification of the input precursor and pyrolysis product, respectively, allows targeted design of the physicochemical properties and sorption characteristics of the resulting sorbent. The present work deals with the preparation of pyrolysis materials based on unmodified cattail leaf biomass (BC) and its Mg-modified analogue (MgBC) by a slow pyrolysis process at 500 °C and a residence time of 1 h in a pyrolysis reactor. Physicochemical characterization of BC and MgBC carried out by pH, total C, N, surface size analysis (SSA), 13C NMR, SEM-EDX and XRD confirmed significant morphological and mineralogical differences between the prepared sorbents. By performing sorption experiments using a model anionic analyte (As) and application of Langmuir isotherm, we found that the predicted maximum sorption capacity of MgBC for As is 13.5-fold higher than that of BC. The sorption process of As by both sorbents is best described by the Sips adsorption isotherm (R2 ≥ 0.995) and a pseudo-nth order kinetic model (R2 ≥ 0.997). The optimum pH for As sorption by BC and MgBC sorbents is in the interval 5–6. The presence of competitive phosphate anions (equimolar concentration of 1:1) in the solution significantly reduces the sorption capacity of MgBC for As by 40% for BC by 70%. The presence of Cl- ions showed no significant effect on the sorption capacity of Bc and MgBC for As. Both sorbents were best recovered using 0.1 mol/L NaOH solution when the desorption efficiency for both sorbents was more than 95%. The MgBC sorbent showed 35% retention of As from the real sample in the model SPE column at a flow rate of 0.12 mL/s. Based on the obtained knowledge, it is evident that biochar-based sorbent prepared from Mg-modified precursor represents an effective sorbent for anionic forms of analytes and opens the possibility of its use also in preconcentration and separation techniques.