Freundlich Adsorption Research Articles

Enhanced copper-adsorption removal from water by easy-handling silica aerogel-polyurethane foam composites

Safe water supply has become one of the main concerns of our society due to the intense industrial activities generating hazardous waste. Among the water pollutants, copper ions are known for potential diseases caused by accumulation of this metal. Therefore, different adsorbents have been produced for this purpose, highlighting aerogels for their effective adsorption owing to their high surface areas and porosity. Herein the synthesis of a novel silica aerogel-based composite for copper removal is described. It was produced by the sol–gel technique, synthesizing the silica aerogel into a reticulated-polyurethane foam that acted as a macrocellular skeleton, preventing a strong shrinkage of the aerogel during the ambient pressure drying. The produced aerogels and composites were characterized in terms of density, textural properties, hydrophobicity, and copper removal efficiency. Isotherm studies revealed a significantly improved adsorption capacity in comparison with the monolithic aerogel, reaching a maximum value of 46.13 mg g−1. The predominant adsorption mechanism was Langmuir- Freundlich adsorption. The adsorption kinetics were also evaluated by different models, as well as the ability to function as filtration medium. Therefore, this work provides a promising strategy for copper uptake avoiding tedious filtration steps to separate the adsorbent, thus reducing time and costs.

Biomass of Anthonotha macrophylla leaf extract as a mild steel acid corrosion inhibitor: Experimental and theoretical study

This study investigated weight loss and electrochemical impedance spectroscopy (EIS) to explore the inhibition potential of Anthonotha macrophylla leaf extract (AME) on mild steel corrosion in 0.5 M H2SO4 medium. The result shows that the highest inhibition efficiency of 90.47 % at 303 K and 80.02 % at 333 K were obtained. At temperatures of 303 K and 333 K, it was discovered that the corrosion rate decreased as the concentration of the AME inhibitor rose from 0.1 g/L (7.73×10−4gcm−2hr−1) to 0.5 g/L (2.27×10−4 gcm−2hr−1). The result of the EIS measurement is in consistent with that of the weight loss method. Adsorption isotherms portrayed that Tempkin and Freundlich's adsorption isotherms were obeyed. Calculated values of Ea, ∆Hads and ∆Gads suggested a physical adsorption mechanism. FTIR, SEM-EDX, and XRD measurements revealed that the AME inhibitor efficiently shields the mild steel surface from further corrosion attack by inducing the formation of passivated film on the mild steel surface. The calculated quantum parameters correlated with experimental results, thus, AME can be used as an alternative inhibitor for the protection of mild steel against corrosion.

The effective treatment of dye-containing simulated wastewater by using the cement kiln dust as an industrial waste adsorbent

This study compares the adsorption behavior of both Methylene Blue (MB) and Congo Red (CR) dyes on the surfaces of cement kiln dust (CKD) powder from the experimentally simulated wastewater solution. The cement kiln dust powder was characterized using X-ray Fluorescence (XRF), X-ray diffraction (XRD), N2 adsorption–desorption Brunauer–Emmett–Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) tests. The adsorption for such dyes was studied under varying mixing contact times, temperatures, and pH as well as various initial concentrations of both dyes and adsorbent using the batch mode experiments. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were applied, and the results revealed that the pseudo-second-order fitted well to the kinetic data. Thermodynamic parameters stated that the adsorption process was endothermic. Studying Linear and nonlinear forms of Langmuir and Freundlich's adsorption isotherms revealed that the adsorption process was followed by both homogeneous mono-layer and heterogeneous multilayer coverage on the active sites of cement kiln dust particles. The data showed that the adsorption capacities of the methylene blue and Congo red dyes were 58.43 and 123.42 mg/g, respectively and cement kiln dust is an adsorbent with little cost for the treatment of wastewater.

Adsorption of antiretroviral drugs, abacavir, nevirapine, and efavirenz from river water and wastewater using exfoliated graphite: Isotherm and kinetic studies

In this work, exfoliated graphite was used to adsorb antiretroviral drugs from river water and wastewater. The exfoliated graphite was prepared from natural graphite by intercalating it with the acids and exfoliating it at 800 °C. It was characterized using Fourier Transform Infrared Spectroscopy which showed phenolic, alcoholic, and carboxylic functional groups between 1000 cm-1 and 1700 cm-1. Energy-dispersive X-ray spectroscopy results showed carbon as the main element with splashes of oxygen. The Scanning Electron Microscopy images showed increased c-axis distance between graphene layers after intercalation, which further increased after the exfoliation. The exfoliation resulted in elongated distorted cylinders, which were confirmed by the lower density (0.0068 g/mL) of exfoliated graphite material compared to the natural graphite (0.54 g/mL). The X-ray diffraction pattern showed the characteristics of hexagonal phase graphitic structure by the diffraction plane (002) at 26.74°. Raman spectroscopy results showed the natural graphite, graphite intercalated, and exfoliated graphite contained the D, G, D′, and G′ peaks at about 1350 cm-1, 1570 cm-1, 2440 cm-1, and 2720 cm-1, respectively indicating that the material's crystallinity was not affected by the modification. The highest antiretroviral drugs removal (95–99%), from the water was achieved with a solution pH of 7, an adsorbent mass of 30 mg, and an adsorption time of 30 min. The kinetic model and adsorption isotherm studies showed that the experimental data fit well in pseudo-second-order kinetics and is well explained by Freundlich's adsorption isotherm. The maximum adsorption capacity of the exfoliated graphite for antiretroviral drugs ranges between 1.660 and 197.0, 1.660–232.5, and 1.650–237.7 mg/g for abacavir, nevirapine, and efavirenz, respectively. The obtained removal percentages were 100% in river water, 63–100% in influent and 70–100% in effluent wastewater unspiked samples.

Cleaner reactive dyeing with the recycled dyeing wastewater

In order to recycle water and inorganic salts, sodium persulphate (SPS) was used to degrade the C.I. Reactive Red 195 (RR195) dyeing wastewater. The thermodynamic and kinetic relationships of RR195 dyeing in cleaner and conventional dyeing processes were analyzed and compared. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization, color parameters and energy conservation. The appropriate conditions were 0.3 g/L of SPS and treatment at 95 °C for 30 min, which resulted in a decolorization rate of 99.7% for the dyeing wastewater, mainly due to the action of radical sulfate. When cotton fabric was dyed with the cleaner dyeing, the kinetic was pseudo-second-order and the thermodynamic was Freundlich adsorption. There was a 47.5% reduction in half dyeing time, a greater diffusion coefficient and standard affinity, and lower entropy and enthalpy values when dyeing in reused wastewater. Cotton fabrics were dyed with the proposed cleaner dyeing process, which reduced the amount of water and inorganic salt by 95.8% and 89.8%, respectively. The total organic carbon (TOC), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were 53.6%, 69.8% and 42.6% lower than the conventional dyeing process, respectively. The recommended technology not only reduces the amount of dyeing wastewater but also enables the recycling of inorganic salts and water, which makes great progress in the textile industry.

Evaluation of combined addition of nitrite and chloride on the corrosion behavior of steel bars in modified magnesium oxysulfate cement paste

Magnesium oxysulfate (MOS) cement, a new breed of eco-friendly and carbon-efficient material, boasts exceptional corrosion resistance, especially in harsh environments such as high salt and high humidity. Understanding how it affects the corrosion of steel bars is crucial for its widespread application in coastal concrete engineering. Nitrite-based inhibitors are known for their rust-preventing qualities in cementitious materials. However, more research is needed to determine if nitrite remains effective in MOS cement mixed with chloride salts. This study focuses on the combined effect of chloride and nitrite salts on the corrosion of steel bars in MOS cement. Methods like corrosion area rate, weight loss rate, natural potential, and electrochemical station are employed to study the corrosion behavior of steel in MOS cement. Microscopic techniques help unravel the influence mechanism of phase composition and microstructure on these materials. Furthermore, the study examines how chloride and nitrite contents affect the concentration of free nitrite and chloride ions in MOS cement paste. The analysis model is also established to compare simple linear adsorption, Langmuir adsorption, and Freundlich adsorption. The results indicate that chloride accelerates steel corrosion, while nitrite slows it down in the environment of mixed chloride and nitrite. In low-chloride environments, nitrite content has minimal impact on steel corrosion, but its effect becomes more pronounced in high-chloride settings. The MOS cement mixed with chloride and nitrite primarily consists of Mg(OH)2, MgCl2, MgCO3, MgO, and the 5Mg(OH)2·MgSO4·7 H2O (517 phase). The phase content of passive film on the surface of steel bar is composed primarily of Fe2O3, FeO, Fe, and FeOOH in descending order. As nitrite content increases, the absorption and concentration of free nitrite ions in the MOS cement paste gradually rise, exhibiting a linear trend. Based on the fitting calculations for three distinct adsorption relationships, notably, due to the limited adsorption capacity of MOS cement for nitrite, there's a considerable difference between the simple linear adsorption relationship and the two nonlinear adsorption models in high nitrite environments. However, in low nitrite concentrations, the difference among these three fitting adsorption relationships is little. This research can provide theoretical basis for enhancing the corrosion resistance and durability of coastal concrete engineering with high chloride exposure.

Biochar from waste green coffee extracted bioactive compounds as materials for ammonium adsorption

This study investigates the adsorption potential of AC-GCB biochar, obtained by pyrolyzing green coffee extracted bioactive compounds at 400 ºC, for ammonium removal from groundwater. The biochar's microstructure was characterized using scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and Energy dispersive spectrometry (EDS) Mapping. Optimal adsorption conditions were observed at an initial pH range of 4 to 8, an initial NH4+ concentration of ≤ 25 mg.L-1, and a biochar dose of 10 g.L-1. The ammonium adsorption of AC-GCB was consistent with both Langmuir and Freundlich's adsorption theories (R2 > 0.92). The AC-GCB biochar obtained the maximum adsorption capacity Qm was 14,48 mg.g-1, higher than the control BC-GCB biochar that pyrolysised without bioactive compound extracted with Qm was only 5.41 mg.g-1.

Think before throw: waste chili stalk powder for facile scavenging of cationic dyes from water.

Chili stalk powder (CS), a non-conventional adsorbent, has been exercised for facile removal of cationic dyes from simulated and wastewater by batch technique. The prepared material has been characterized by Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller analysis (BET), powder X-ray diffraction (powder XRD), and pHZPC and tested best with methylene blue and crystal violet under ambient conditions. FTIR denotes the presence of carbonyl and polyphenolic groups, responsible for dye adsorption. BET surface area analysis evaluates the porous nature and specific surface area of the material, and powder XRD confirms its amorphous nature. The porous structure could be ascertained from the FESEM image, and energy dispersive X-ray analysis (EDX) confirms the elemental composition. The pH above pHzpc shows an increase in removal efficiency. The maximum adsorption capacities are 49.53 and 36.88mg/g for methylene blue (MB) and crystal violet (CV) respectively. Linear as well as non-linear plots for kinetic and isotherm models were studied. Both dye uptake fits the linear plot of Langmuir adsorption isotherm (R2 = 0.999 and 0.995) and pseudo-second-order kinetics (R2 = 0.998 and 0.999). In the non-linear plot, the adsorption process for both dyes fit Langmuir (R2 = 0.999 for MB and R2 = 0.983 for CV) as well as Freundlich adsorption (R2 = 0.999 for MB and R2 = 0.994 for CV). 75.48% crystal violet (CV) and 73.35% methylene blue (MB) regeneration were successful in 1:1 methanol medium and reused for up to three cycles. The uptake mechanism is suggested to be a union of π-π stacking, electrostatic interaction, and weak hydrogen bonding. The material was tested with industrial effluent to prove its application in real wastewater treatment. Moreover, the material shows superior adsorption capacity than contemporary phytosorbents. To conclude, a zero-cost adsorbent using green chili stalk has been demonstrated for wastewater treatment.

Integrating rod‐shaped nickel molybdate@polypyrrole matrix for sustainable adsorptive removal of organic dye: Kinetics, isotherm, and thermodynamics study

AbstractWater pollution presents a significant global challenge that impacts the environment. The release of industrial effluents significantly contributes to this. Adsorption studies offer a sustainable and cost‐effective solution to efficiently remove organic pollutants from water. The current study comprises a polypyrrole/nickel molybdate composite for the effective adsorption of organic dyes, such as methylene blue, from aqueous solutions. The catalyst has been comprehensively characterized using various techniques, including XRD, FE‐SEM, FT‐IR, HR‐TEM, XPS, BET, TGA, zeta potential, and DLS analysis. Adsorption studies demonstrate up to 97% removal efficiency in 60 min. This study also evaluates the impact of various parameters, such as temperature, pH, dye concentration, and quantity of the catalyst, on the adsorption efficiency. The R2 value of 0.99 that is obtained in the kinetics study suggests the suitability of the adsorption process toward pseudo‐second‐order kinetics. The adsorption isotherm study reveals that the adsorption follows Freundlich's adsorption isotherm. The maximum adsorption capacity of the study is found to be 17.76 mg/g. Investigations into thermodynamic study give a ∆H value of −19.21 J/mol K, indicating the exothermic behavior, and ∆G of −6.95 KJ/mol, suggesting the spontaneity of the composite during the adsorption process. These results demonstrate the potential of the developed material as an effective adsorbent for removing organic dyes from water sources.

Efficient adsorption of anionic and cationic dyes by PVA/PAA/GO composite hydrogel with three-dimensional porous double network structure

Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were introduced into graphene oxide (GO) by a water bath method, and PVA/PAA/GO (PPG) with a three-dimensional double network structure was prepared under the action of hydrogen bonding. With the help of a large number of oxygen-containing functional groups and a three-dimensional double network structure in the PPG composite hydrogel, the adsorption performance of anionic and cationic dyes was greatly improved, and the adsorption rates of 100 mg∙L−1 malachite green (MG) and Congo red (CR) within 6 min were 93 % and 55 %, respectively. For comparison, the adsorption rates of MG and CR by graphene hydrogel alone within 30 min were only 10 % and 48 %, respectively. Meanwhile, the free radical polymerization of PAA and PVA also effectively improved the mechanical strength of the graphene hydrogel, and the PPG remained structurally stable under the action of 800 g of gravity. The results of adsorption kinetics showed that the adsorption process of PPG on CR and MG was in accordance with Freundlich adsorption and pseudo-second-order kinetic adsorption. Based on the X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) results, the adsorption performance of PPG mainly originated from physical adsorption, electrostatic attraction, hydrogen bonding and π-π conjugation.

Simultaneous adsorption of amoxicillin and ciprofloxacin on agricultural soils and by-products used as bio-adsorbents: Unraveling the interactions in complex systems

The presence of pharmaceuticals in agricultural soils, like amoxicillin (AMX) and ciprofloxacin (CIP), poses a significant environmental challenge with potential implications for ecosystems and human well-being. This study explores the simultaneous adsorption of AMX and CIP on crop soils and bio-adsorbents, focusing on competitive adsorption dynamics. Tests were conducted with varying pharmaceutical concentrations in six soils and three bio-adsorbents. CIP consistently exhibited higher adsorption than AMX, particularly at higher concentrations. In the binary system, AMX's adsorption exceeded the individual system at higher concentrations, implying a synergistic effect. Bio-adsorbents, especially pine bark and oak ash, displayed superior adsorption capacities compared to soils. Some soils exhibited enhanced adsorption and retention of both antibiotics simultaneously, aligning with the cooperative adsorption model. Freundlich's adsorption model described the competitive adsorption systems well. These findings have implications for addressing antibiotic contamination in agricultural ecosystems, offering insights into complex interactions in soil environments amid rising pharmaceutical concerns.

A potential remediation of total petroleum hydrocarbon from contaminated soils using surfactant suspended multiwall carbon nanotubes

The spill of crude oil on the soil contaminates it, causing cancer, a dearth of vegetation, livestock deaths, and forced migrations. The petroleum hydrocarbon (TPH) was removed from the soil by ultrasonication of MWCNTs (Multiwalled Carbon Nanotubes) only, MWCNTs + IONP (Iron Oxide Nanoparticles) and MWCNTs + IONP + PEG (Polymer Nanocomposite (P.N.C)) in a laboratory batch adsorption experiment with Triton X 100 surfactant. The effects of contact time, agitation speed, adsorbent dosage and pH was studied. Results showed varied and high removal rate for the three adsorbent suspensions at different parameter. The highest removal percentage was 91.37% at pH 2 for MWCNTs + IONP and 90.72% at 90 min contact time for MWCNT only, while 85.56% was observed for P.N.C at 0.01g adsorbent dosage. However, all three adsorbent suspensions exhibit high removal rates regardless of the parameters studied. In this case, Freundlich's adsorption isotherm was the most accurate description of the process, while pseudo-second order fit the kinetic data more accurately.

Effective removal of Rhodamine B using the hydrothermal carbonization and citric acid modification of furfural industrial processing waste

ABSTRACT In this study, the removal of RhB from water by furfural residue (FR) biochar was prepared by hydrothermal carbonization (HTC) and citric acid (CA) modification and named this biochar as CHFR (C refers to citric acid, H refers to hydrothermal carbonization and FR is furfural residue). The CHFR were characterized by SEM, FT-IR and XPS, and CHFR was investigated by the effects of initial concentration, adsorbent dosage, pH, and contact time on the removal of RhB, and the experimental data were analyzed using the adsorption isotherm models, the adsorption kinetic models and thermodynamics, et al. The results showed that CHFR has strong adsorption performance, and the theoretical maximum adsorption capacity of RhB was 39.46 mg·g−1 under the reaction conditions of pH3, the dosage of 1.5 g·L−1, and 120 min contact time, with a removal efficiency close to 100%. the adsorption of RhB by CHFR is spontaneous and endothermic, which is consistent with the Freundlich adsorption, and the isotherm model fits well with the pseudo-second-order model, and the adsorption rate could still be as high as 92.74% after five regenerations, therefore, CHFR is an environmentally friendly and efficient adsorbent with excellent adsorption regeneration performance.

Investigation on water defluoridation via batch and continuous mode using Ce–Al bimetallic oxide: Adsorption dynamics, electrochemical and LCA analysis

With variable atomic ratios, Ce–Al bimetallic oxides were fabricated using the sol-gel combustion method and utilized for efficient fluoride removal. The synthesized bimetallic oxides were extensively studied using advanced characterization techniques, including TGA, XRD, FTIR, BET surface area analysis, EDX-assisted FESEM, XPS and impedance analysis. These techniques facilitate the interpretation of the chemical and physical properties of the synthesized material. The Ce–Al (1:1) bimetallic oxide was selected as an adsorbent for the defluoridation. The Ce–Al (1:1) oxide demonstrates a moderately high surface area of 108.67 m2/g. The sorption behaviour of fluoride on Ce–Al (1:1) was thoroughly investigated using batch and column modes. The maximum fluoride removal efficiency (99.4%) was achieved at a temperature of 45 °C and pH of 7.0 using an adsorbent dose of 0.18 g/L for 35 min. Pseudo-second-order kinetic model appropriately describes the sorption process. Freundlich's adsorption isotherm was more pertinent in representing fluoride adsorption behaviour. The maximum fluoride adsorption capacity is 146.73 mg/g at 45 °C. Thermodynamics study indicates fluoride adsorption on Ce–Al (1:1) bimetallic oxide is spontaneous and feasible. The adsorption mechanism was interpreted through XPS spectra, indicating that the physisorption process is mainly responsible for fluoride adsorption. An in-depth investigation of the adsorption dynamics was carried out using mass transfer models and found that the external diffusion process limits the overall adsorption rate. An electrochemical investigation was performed to understand the effect of fluoride adsorption on the electrochemical behaviour of bimetallic oxide. The fixed-bed column adsorption study suggested that the lower flow rate and increased bed height favourably impacted the overall defluoridation process, and column adsorption results were suitably interpreted through both the Adam–Bohart model and Yoon–Nelson dynamics model. The sustainable aspect of the defluoridation process was elucidated in terms of carbon footprint measurement using life cycle assessment analysis. The carbon footprint of the entire treatment process was calculated as 0.094 tons/year.

Biosorption of pollutants from chemically derived wastewater using Microcoleus sp.

Abstract Microcoleus sp. is a versatile microorganism widely available in the environment and easily culturable. Hence, there is a progressing demand for wastewater treatment using this novel biosorption medium. The design of such a treatment method may be defined as an optimisation problem of algal dose and hydraulic retention time for attaining an adequate removal efficiency of heavy metals (Cr6+, Ni2+, and Zn2+) and nutrients (PO43- and NO3-). Batch experiments on synthetic wastewater were conducted for algal doses varying from 0.5 to 25 g/L and hydraulic retention times from 1 to 7 days. Significant removal efficiencies of greater than 90% were observed for the heavy metals, 75% of PO43- removal, and no removal of NO3- was found under continuous daylight. The single-factor ANOVA test confirms the statistical significance of the varying parameters on the pollutant removal efficiency. Langmuir and Freundlich's adsorption isotherms indicate satisfactory adsorption of the contaminants about the separation factor and the adsorption intensity constant. The R2 > 0.67 and RMSE < 0.21 suggest a good fit of the modelled data. Following this, the study suggests that the use of Microcoleus sp. is a prospective bioremediation technique for industrial and municipal wastewater.

Waste Tea Leaves as an Adsorbent for the Removal of Heavy Metal Ions from Aqueous Solutions: Quantitative Estimation using Spectrophotometry and Titrimetry

The rapid increase in industrialization and globalization in the last few decades has led to increased disposal of heavy metals in the environment leading to severe water and soil contamination. Among all known pollutants, heavy metals are especially notorious due to their high toxicity, persistent and bioaccumulative nature. Heavy metal toxicity is a major threat and therefore its removal and remediation require special attention to protect human, animal and plant health and to restore soil and water quality. Waste tea leaves (Camellia sinensis) are low-cost adsorbents and their use for the removal of heavy metal ions is likely to address the problems of waste management and heavy metal ion toxicity. In the present study, we have tested the efficacy of waste tea leaves for the quantitative removal of heavy metal ions like Ni(II) and Pb(II) from their aqueous test solutions using spectrophotometric and titrimetric methods respectively. With 5 g tea leaves in the Ni(II) solution, the removal percentage of the ion was found to be 85.56%. From a Pb(II) containing test solution, 286 ppm of the ion was adsorbed by the same amount of tea leaves. The amount of adsorbent dose was found to be directly related to the removal percentage of the metal ion. However, after reaching a threshold, increasing the adsorbent dose has only a negligible effect on adsorption. The adsorption was found to be primarily physisorption and follows Freundlich's adsorption isotherm. The zero-cost and easy availability of waste tea leaves make it a substrate of interest that can be used for the cost-effective removal of heavy metal ions from water and soil.

Phenolic Compounds Removal from Olive Mill Wastewater Using the Composite of Activated Carbon and Copper-Based Metal-Organic Framework.

As the industry of olive oil continues to grow, the management of olive mill wastewater (OMW) by-products has become an area of great interest. While many strategies for processing OMW have been established, more studies are still required to find an effective adsorbent for total phenolic content uptake. Here, we present a composite of a Cu 1,4-benzene dicarboxylate metal-organic framework (Cu (BDC) MOF) and granular activated carbon (GAC) as an adsorbent for total phenolic content removal from OMW. Experimental results demonstrated that the maximum adsorption capacity was 20 mg/g of total phenolic content (TPC) after 4 h. using 2% wt/wt of GAC/Cu (BDC) MOF composite to OMW at optimum conditions (pH of 4.0 and 25 °C). The adsorption of phenolic content onto the GAC/Cu (BDC) MOF composite was described by the Freundlich adsorption and pseudo-second-order reaction. The adsorption reaction was found to be spontaneous and endothermic at 298 K where ΔS° and ΔH° were found to be 0.105 KJ/mol and 25.7 kJ/mol, respectively. While ΔGº value was -5.74 (kJ/mol). The results of this study provide a potential solution for the local and worldwide olive oil industry.

Potential of Corn Stalk Biomass as Biosorbent in Adsorption of Mercury (Hg) Metal Contaminants

Corn stalks are an agricultural waste that is commonly found in Indonesia. Corn stalks have a high enough cellulose content which has functional groups that can be used as biosorbents. This study aims to optimize the adsorption of corn stalk waste to mercury metal ions and then determine the adsorption capacity and adsorption constant of the Langmuir and Freundlich isotherm model. This research begins with corn stalk preparation, delignification, characterization using FTIR and SEM, determination of optimization of biosorbent weight, pH of Hg solution, contact time, and concentration of Hg solution, then applied to mercury metal contamination waste. Optimization of the weight of biosorbent in the range 0.4-1.2 grams, pH of the Hg solution is 2-4, contact time is 60-120 minutes, and concentration of the Hg solution of 30-100 g/L with a solution volume of 50 mL. Furthermore, determination of mercury levels, manufacture of standard series, and testing using ICP-OES. Followed by the determination of Langmuir and Freundlich's adsorption isothermal model. The results of this study indicate that the optimum conditions for the adsorption process occur at the weight of the biosorbent 1.2 grams, pH of the Hg 3 solution, contact time of 90 minutes, and concentration of Hg solution of 40 ppb with a solution volume of 50 mL. The application of biosorbent to metal contamination waste with adsorbed Hg concentration obtained 27.5772 ppb in 50 mL of waste solution with an adsorption efficiency of 88.44%. In the determination of Langmuir and Freundlich isotherms, a match was found for Langmuir adsorption isothermals with an adsorption capacity of 0.00333 mg Hg/g biosorbent and b = 176.8256.

Adsorption characteristics of six bisphenol compounds on magnetic three-dimensional nitrogen-doped carbon nanomaterials and their use in effervescent reaction-assisted dispersive microextraction

Herein, we successfully prepared magnetic Co/Ni-based N-doped 3D carbon nanotubes and graphene nanocomposites (CoNi@NGC) using a simple high-temperature calcination method. The CoNi@NGC nanocomposites were used as adsorbents to study their adsorption performances and underlying kinetic mechanisms for six types of bisphenol compounds (BPs) in water. They were also used as extractants, and acid-base effervescent tablets were used to enhance extractant dispersion with the aid of vigorous CO2 bubbling. Thus, a novel pretreatment method was developed, denoted effervescent reaction-assisted dispersive solid-phase microextraction (ER-DSM), which was combined with high performance liquid chromatography-fluorescence detection (HPLC-FLD) to rapidly quantify trace-level BPs in several drinks. The morphology and structure of the CoNi@NGC adsorbent were characterized in detail using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET-BJH), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The CoNi@NGC nanocomposites were successfully doped with N and exhibited large specific surface areas (109.42 m2/g), abundant pores, and strong magnetic properties (17.98 emu/g).Key parameters were rigorously optimized to maximize the adsorption performance of CoNi@NGC, including adsorbent dosage, solution pH, temperature, and time. Under the constant conditions of pH=7, 5 mg of CoNi@NGC, initial BP concentrations of 5 mg/L, and 5 min of shaking at 298 K, the adsorption percentages of bisphenol M (BPM) and bisphenol A (BPA) reached respective maxima of 99.01% and 98.21%. Remarkably, those of bisphenol Z (BPZ), BPA, and BPM reached almost 100% after 90 min. The adsorption between the BPs and CoNi@NGC was mainly governed by hydrogen bonds, electrostatic interactions, and π-π conjugation. The entire adsorption process was consistent with Freundlich adsorption and a quasi-second-order kinetic equation, representing spontaneous adsorption. Via integration with HPLC-FLD, ER-DSM was used to rapidly extract and analyze trace-level BPs in six types of boxed drinks. Critical factors were optimized individually, including the type of eluent and elution time and volume, which influenced the enrichment effect. Under the optimized extraction conditions (pH=7, 5 mg CoNi@NGC, elution with 2 mL acetone for 6 min), the limits of detection and quantification of the novel extraction method were 0.06-0.20 and 0.20-0.66 μg/L, respectively. The intra- and inter-day precisions spanned the ranges 1.44%-4.76% and 1.69%-5.36%, respectively, and the recoveries in the actual samples were in the range 82.4%-103.7%. Moreover, the respective residual levels of BPA and BPB in peach juice samples were 2.09 and 1.37 μg/L. Regeneration studies revealed that the CoNi@NGC adsorbent could be reused at least five times, which significantly reduced the cost of evaluation. In summary, compared to other methods, this method displays the advantages of a high sensitivity, rapid extraction, and environmental friendliness, thereby exhibiting considerable potential for use in conventional monitoring of trace-level BPs in food matrices.

Reduction of sulphur dioxide emission into the environment by adsorption on enhanced α-hematite surface.

The top priority of the sustainable development goals is to improve the quality of the environment for better living. Sulphur dioxide is considered more hazardous than any other gases that pollute the environment and harm the well-being of organisms. In 2019, India alone accounted for 21% of the world's SO2 emissions. Strict action is required to reduce maximum levels of SO2 emission to the atmosphere to improve the total air quality. To reduce SO2 emissions more effectively, in this study, α-hematite was chemically activated by using 5% NaOH and C2H5OH with the help of a double bed adsorption column. The adsorbent properties of α-hematite were studied by Brunauer-Emmett-Teller isotherm, which revealed a high surface area (539 m2g-1), and pore size (2.3125nm) and high volume in the pore (0.0293432 cm3mg-1). FTIR confirmed that the SO2 particulate on the surface of the adsorbent with an adsorption capacity of 95%. The operating temperature of 40-50°C was optimal for the chemical adsorption. It was found that the inlet concentration (64mgm-3) of SO2 decreases as the adsorption of SO2 increases. Trace SO2 was well-adsorbed by the adsorbent, which resulted in a mass transfer zone. Freundlich's adsorption spectrum was more fit for low concentrated SO2 than Langmuir isotherm. The results indicate that the environmental emission of SO2 can be reduced with chemically enhanced α-hematite.