Pseudo-second Order Research Articles

Effective removal of Pb (II) from wastewater by zinc-iron bimetallic oxide-modified walnut shell biochar: A combined experimental and DFT calculation approach

The modified walnut shell biochar (WBC) was prepared through zinc-iron bimetallic oxide modification (ZF@WBC) at 600 °C under oxygen-limited conditions in this study. Through adsorption experiments, characterization analyses, and density functional theory (DFT) calculations, the adsorption properties of ZF@WBC to Pb (II) were investigated and the mechanism underlying such adsorption was elucidated. Characterization results showed that the surface area (375.9709 m2/g) and total pore volume (0.205319 cm3/g) of ZF@WBC were significantly greater than those of walnut shell biochar. The maximum adsorption capacity of ZF@WBC for Pb (II) was found to be 104.26 mg/g, which is 2.57 times higher than that of WBC according to the adsorption experiments conducted. The observed adsorption behavior followed both the pseudo-second-order (PSO) kinetic model and Langmuir isothermal adsorption model, suggesting that chemisorption plays a major role in the absorption process. Based on SEM, XRD, XPS, FTIR characterizations along with DFT calculations performed in this study, it can be concluded that surface complexation, ion exchange, electrostatic attraction, physical absorption are among the main mechanisms responsible for absorption of Pb (II) by ZF@WBC. Furthermore, even in the presence of interfering ions at different concentrations, ZF@WBC exhibited a removal rate above 70% for Pb (II). Therefore, ZF@WBC has great potential as an effective absorbent for removing Pb (II) from wastewater, while also offering opportunities for biomass waste resource utilization.

Repurposing disposed surgical face masks into activated carbon for efficient sorption of bio recalcitrant malathion pesticide

Pesticides are essential for enhancing agricultural produce, but their excessive use poses risks to ecosystems due to persistence and toxicity. This study explores repurposing disposed surgical face masks (DSFMs), rich in polypropylene (PP), as a precursor for activated carbon (AC) synthesis, addressing plastic pollution. DSFM pieces were subjected to hydrothermal treatment with sulfuric acid and KOH activation, optimized via response surface methodology (RSM). Optimal AC preparation conditions were achieved at 800 °C, PP/KOH ratio 3 g/g, and 50 min resulting in AC (3AC800-50) with BET surface area 892.16 m2/g and pore volume 0.6353 cm3/g. The resulting carbon material demonstrated excellent adsorption affinity towards malathion pesticides (MP) with a capacity of 536.68 mg/g. The Freundlich adsorption model accurately fits the data with a high R2 of 0.9898. Kinetic analysis revealed the pseudo-second-order (PSO) model as the best fit, with negative ∆G° indicating the spontaneous nature of MP adsorption. These findings highlight the potential of utilizing ACs derived from DSFMs for sustainable plastic waste management and pesticide removal from water.

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.

A facile and green synthesis of corn cob-based graphene oxide and its modification with corn cob-K2CO3 for efficient removal of methylene blue dye: Adsorption mechanism, isotherm, and kinetic studies

In recent years, the treatment of synthetic dyes has become an environmental concern. In this study, a single step calcination process was used to develop the inventive, simple, and inexpensive adsorbent CC-GO/CC-K2CO3 composite. The composite was employed for the treatment of methylene blue (MB), a cationic dye. Several characterization methods including powder XRD, FTIR, XPS, BET, FESEM, EDX, Raman, and HRTEM techniques were utilized for the analysis of the composite. The surface area and mean pore diameter of CC-GO/CC-K2CO3 were 32.651 m2 g−1 and 3.71 nm, respectively. The adsorption experiment showed that optimal parameters for the removal of MB dye are at an adsorbent dose of 60 mg, initial dye concentration of 80 mg/L, contact time of 150 min, and pH value of 12 at room temperature. Under optimized conditions, CC-GO evidences a removal efficiency of 70.34 ± 1.36 % while after incorporation with CC-K2CO3 the removal capacity sharply increases up to 98.10 ± 0.4 %. Kinetic and isotherm models were used to analyze the removal rate constant and equilibrium adsorption capacity under various adsorption environments. The adsorption study was found to follow the models of pseudo-second order kinetic and Freundlich isotherm. The CC-GO/CC-K2CO3 composite has the maximum adsorption capacity (MAC) of 160.77 mg/g established by the Langmuir isotherm. The prepared composite has demonstrated the capacity to be recycled up to three times with a gradual decrease in its adsorption behavior, exhibiting removal efficiency of 61.66 ± 2.04 %.A cost estimation study of the composite was also performed to assess its cost effectiveness.

Efficient phosphate removal from water using ductile cast iron waste: a response surface methodology approach.

Water scarcity is a critical issue worldwide. This study explores a novel method for addressing this issue by using ductile cast iron (DCI) solid waste as an adsorbent for phosphate ions, supporting the circular economy in water remediation. The solid waste was characterized using XRD, XRF, FTIR, and particle size distribution. Wastewater samples of different phosphate ion concentrations are prepared, and the solid waste is used as an adsorbent to adsorb phosphate ions using different adsorbent doses and process time. The removal percentage is attained through spectrophotometer analysis and experimental results are optimized to get the optimum conditions using Design Expert V13. The pseudo-second order (PSO) kinetics model and Langmuir isotherm were fitted with the experimental results with maximum adsorption capacity (qmax = 0.28mg/g). The thermodynamic analysis indicated that this adsorption process was spontaneous based on the negative value of Gibbs free energy (∆G). Additionally, the positive values of enthalpy (∆H) indicated the endothermic nature of this adsorption system. It was able to reach the highest adsorption percentage of 98.9 (%) for phosphate ions from aqueous solutions using response surface methodology (RSM) with optimum conditions of 10mg/L phosphate ion concentration, pH = 8, normal room temperature, 9min adsorption, and 0.5g/L adsorbent dosage.

Insights into the adsorption mechanism of chlorpyrifos on activated carbon derived from prickly pear seeds waste: An experimental and DFT modeling study

The removal of chlorpyrifos (CPF) from water was achieved using activated carbon (AC) derived from prickly pear seeds (PPS) wastes, developed through chemical activation with phosphoric acid. Several physico-chemical characterization methods were employed. The determination of surface functions using the Boehm assay indicated that the processed AC predominantly possesses acidic functions. The results obtained from the Boehm assay were corroborated by the pH value of the point of zero charge (pHpzc), which was equal to 2.5. Specific area calculation by the BET (Brunauer Emmett Teller) method revealed a large specific area (SBET) of 1077.66 m2 g⁻1. Adsorption experiments of CPF on AC demonstrated that the pseudo-second order (PSO) model and the Freundlich model were the most suitable for kinetic and isothermal modeling, respectively. The maximum CPF adsorption capacity of the PPS AC was found to be approximately 35 mg g⁻1. A theoretical study employing the density functional theory (DFT) was conducted using the B3LYP/6-311G (d, p) method. The most reliable adsorption energy (Eads) and Gibbs free energy (ΔGads) values between CPF and the functional groups on the AC surface were calculated. Results indicated a strong interaction between the lactone group of AC and CPF (ΔGads = −7.15 kcal mol⁻1, ΔEads = −21.55 kcal mol⁻1) and the hydroxyl group (ΔGads = −6.61 kcal mol⁻1, ΔEads = −20.66 kcal mol⁻1). This study demonstrates that activated carbon possesses significant adsorption power, making it highly effective for depolluting water contaminated by pesticides. The application of the theoretical DFT method enhances the understanding of the adsorption phenomenon of CPF on AC.

Biochar-alginate beads derived from argan nutshells for effective methylene blue removal: A sustainable approach to wastewater treatment

This study explores the use of biochar derived from Argan Nutshells as a core component in alginate beads for the removal of methylene blue (MB) from aqueous solutions. The characterization of BC/Alg composite was conducted using techniques like Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), and size distribution to assess its structural properties and confirm the strong interaction between both components. The adsorbent exhibited surface functional groups characteristic of both biochar and alginate, and SEM confirmed the spherical morphology of the beads. A response surface methodology (RSM) was used to optimize the adsorption process by evaluating the effects of key parameters including pH, temperature, adsorbent mass, and dye concentration. The results showed that the BC/Alg effectively removed 96.4 % of MB. The pseudo-second order (PSO) kinetic model best described the MB removal process (R2 = 0.9990), while the Langmuir isotherm model accurately represented the adsorption equilibrium (R2 = 0.96879). After four cycles of regeneration trials, BC/Alg retained 82 % MB removal efficiency, indicating high reusability and stability. The remarkable adsorption capability of BC/Alg showed that it may be employed as an economical and environmentally friendly adsorbent in aqueous solutions, strengthening the case for employing Argan nutshells for water treatment.

Comparison of adsorption potential of methylene blue and 17β-stradiol on biochar, activated biochar and catalytic biochar from lignocellulosic waste

This work compares the adsorption capacity of methylene blue (MB) and 17β-stradiol (17β-S) onto biochar (B), activated biochar (AB) and catalytic biochar (CB), obtained through pyrolysis of residual lignin of the second-generation (2G) ethanol production process from a sugarcane industry. K2CO3 was used as activating agent and catalyst. Biochars were characterized by the techniques of point of zero charge, nitrogen adsorption and desorption, SEM and FTIR. Kinetic, isothermal and thermodynamic adsorption studies were carried out. Biochars behaved according to the pseudo-second order (PSO) kinetic model, with similar removal percentages of MB using AB and CB. In contrast, AB showed significantly higher removal percentages of 17β-S than CB. The Sips model agreed to isothermal adsorption data of 17β-S onto all biochars. For MB adsorption, Freundlich model agreed to data using B and AB, and Langmuir model was more suitable for CB. The process was viable, spontaneous, endothermic and showed increase in entropy, except for 17β-S adsorption onto CB. Consequently, the activated and catalytic pyrolysis processes increased the adsorptive potential of biochar derived from 2G lignocellulosic residue. Finally, CB and AB obtained significant removal percentage values of MB (85.8–99.3 %) and 17β-S (37.6–76.7 %), where CB is favorable due to its simpler preparation steps.

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.

Enhanced adsorption-photodegradation of tetracycline using Ce-N-co-doped AC/TiO2 photocatalyst: isotherms, kinetics, mechanism, and thermodynamic insight.

Excessive use of tetracycline (TC) is alarming owing to its increased detection in water systems. In this study, a photocatalyst was developed to degrade TC using a Ce-N-co-doped AC/TiO2 photocatalyst, denoted as Ce/N-AC/TiO2, prepared using the sol-gel method assisted by microwave radiation, speeding up the synthesis process. Ce/N-AC/TiO2 achieved maximum TC degradation of 93.1% under UV light with optimum sorption system conditions of an initial concentration of 10 mg L-1, pH 7, and 30 ℃, under 120 min. Scavenger experiments revealed that holes and superoxide radicals were the active species influencing the photodegradation process.The TC degradation was appropriately fitted with Langmuir isotherms and a pseudo-second-order (PSO) kinetic model. The change in enthalpy (ΔH) (2.43kJmol-1), entropy (ΔS) (0.024kJmol-1), and Gibbs free energy (ΔG) (- 4.941 to - 5.802kJmol-1) suggested that the adsorption process was spontaneous, favourable, and endothermic. Electrostatic interaction, hydrogen bonding, pore-filling, cationic-π, n-π, and π-π interaction were among the interactions involved between TC and Ce/N-AC/TiO2. Furthermore, Ce/N-AC/TiO2 stability was confirmed through 80% removal efficiency even after the fifth reuse cycle. Notably, this work provides new insight into the production of efficient, reusable, and enhanced photocatalysts using a rapid and cost-effective microwave-assisted synthesis process for pollutant remediation.

Aspergillus versicolor mediated biofabrication of zinc phosphate nanosheets for exploring their antimycotic activity and development of alginate-based nanocomposite for enhanced dye degradation

The production of novel, suitable, and cost-effective nanocomposites are highly required for its prospective application in the remediation of environmental pollutants and as antimycotic agents. Zinc phosphate nanosheets (ZP-ns) were fabricated by harnessing the exometabolites of Aspergillus versicolor and then incorporated within an alginate biopolymer (ZP-ns@Alg) to improve the biosorptive removal of the methyl orange (MthO) dye from its aqueous solution. For the very first time, the antimycotic activity of the green synthesized ZP-ns was unveiled. The mycelial growth inhibition was obtained in a dose-dependent manner with significant (P < 0.05) behavior compared to the control plates. The biosorption conditions using ZP-ns@Alg microbeads were optimized using the response surface methodology-based central composite design (RSM-CCD) to maximize the biosorption efficiency. The highest biosorptive efficiency was achieved at pH 4.0, biosorption dosage 0.07 g, contact time 50 min, dye concentration 100 mg/l, and shaking speed 100 rpm. The equilibrium data were more tailored to the pseudo-second order (PS) model with an R2 of 0.9955 and a Langmuir isotherm (R2 = 0.9945) with a maximum biosorptive capacity (qmax) of 166.95 mg/g and an average RL value of 0.0003, indicating favorable biosorption. The removal capacity was reduced to ∼90 % after the 6th cycle, which is a robust signal that the developed biosorbent microbeads could be recycled and regenerated for a prolonged time. These results marked the application of ZP-ns as a novel antimycotic agent with excellent activities. Microbeads, made from low-cost biopolymers, can be applied to remediating environmental pollutants from wastewater.

A CIRCULAR ECONOMY APPROACH TO PRODUCE LOW-COST BIODIESEL USING AGRO-INDUSTRIAL AND PACKING WASTES FROM MEXICO: VALORIZATION, HOMOGENEOUS AND HETEROGENEOUS REACTION ROUTES AND PRODUCT CHARACTERIZATION

This manuscript describes a circular economy approach to produce low-cost biodiesel using Tetra Pak (TP) and Mexican biomass wastes. Lipids were extracted from non-edible biomass with hexane. Corozo seeds contained 53 wt% lipids, while remaining biomass had <5 wt%. Corozo seed oil was selected to produce biodiesel with both homogeneous and heterogeneous reaction systems. A heterogeneous catalyst was synthesized from TP and its performance was compared with KOH in homogeneous systems using corozo and soybean oils. The best reaction conditions were identified through the Signal/Noise ratio analysis. TP catalyst achieved biodiesel yields of 12.7-98.11% (corozo) and 87.0-98.4% (soybean), while KOH systems showed 7.2-96.3% and 64.6-98.5%, respectively. These reactive systems were endothermic and fit to pseudo-second order kinetic model. Activation energies for KOH-catalyzed systems were 86.89 (corozo) and 43.72 (soybean) kJ/mol, while TP-catalyzed systems showed 78.31 and 105.68 kJ/mol, respectively. TP catalyst reuse was tested, and the loss of catalytic activity was attributed to active sites poisoning. Biomass, catalysts, and reaction products were characterized (e.g., FTIR, ICP, XRD, EDX-SEM, WDXRF, XPS, basicity and nitrogen adsorption isotherms). The TP catalyst showed competitive performance with respect to KOH, contributing to a sustainable biodiesel production chain viable for commercial implementation in Mexico.

Mesoporous TiO2@nitrogen-doped carbon nanosheets implanted in flexible and robust chitosan membrane with dual-function for efficient adsorption of iodide and methyl orange from aqueous solution

Radioactive iodide (I−) and methyl orange (MO) are two leading pollutants in wastewater, posing significant health risks. Crosslinked chitosan membranes (CCM) combined with TiO2@nitrogen-doped carbon nanosheets (CCM/TiO2@NC) were prepared as efficient I− and MO adsorbents in wastewater. These membranes leverage multiple interactions between I−/MO and functional groups (−NH2, nitrogen-doped carbon, and TiO2) within the membrane. As expected, CCM/TiO2@NC exhibited high I− removal efficiencies of nearly 82 % across a wide pH range (pH 3 − 11) and an exceptional MO removal efficiency of 96.1 % at a neutral condition. The adsorption behaviors followed the Langmuir isotherm and pseudo-second order kinetic model for both species, achieving maximum adsorption capacities of 1.383 mmol/g (175.6 mg/g) for I− and 661.4 mg/g for MO, respectively. Additionally, CCM/TiO2@NC maintained a high absorption efficiency for both I− and MO through five regeneration cycles. The I− adsorption mechanism of CCM/TiO2@NC involves electrostatic attraction, anion-π interaction, and hydrogen bonding, while MO adsorption involves electrostatic attraction, n/π-π interactions, and hydrogen bonding. This study offers feasible guidance on developing chitosan/nanomaterial composites as promising adsorbents for removing I− and MO from wastewater.

Valorization of carbon soot ash for the selective capture of lead ions from industrial waste water–A waste to resource approach

Landfills are struggling to accommodate the increasing amounts of carbon soot ash waste from oil refineries. Due to extensive industrial productions, large quantities of lead ions are released into the environment, which not only pollutes the environment but also affects flora and fauna. In this work, these urgent environmental issues will be tackled by studying the use of modified carbon soot ash for specific heavy metal adsorption. Carbon soot ash modified with chemical leaching and physical ball-milling was loaded onto the surface of graphene oxide. This adsorbent was found to selectively adsorb and remove toxic lead ions (>99%) from a mixed heavy metal solution. The adsorption efficiency was found to increase with temperature (20–60 °C) and pH (2–8). Langmuir isotherm and pseudo-second order kinetics were found to fit the adsorption process through curve fitting, where the adsorbent reached a maximum capacity of 194.55 mg/g. Potential mechanisms for lead adsorption and metal specificity are also discussed here. This work aligns with the waste-to-resource pathway, where waste carbon soot ash is diverted from landfilling and is formulated as a specific heavy metal adsorbent, that shows promise for environmental remediation.

Sorption properties of a new modified flax fibre sorbent

The purpose of this study is to develop a modified sorbent of flax waste and investigate its sorption properties towards Cu (II) ions. The authors conducted the modification in two steps. The first step was oxidation of flax fibre cellulose with sodium metaperiodate to dialdehyde cellulose, the second one was the addition of taurine to increase the sorption characteristics of the modified sorbent. The paper presents the conditions for the periodate oxidation reaction of flax fibre and the treatment of the resulting dialdehyde cellulose with taurine. We determined the sorption characteristics of the modified sorbent in comparison with the original flax fibre. Kinetic studies allowed us to establish the time of reaching sorption equilibrium in the heterophase system ‘aqueous solution of metal salt-sorbent’ and determine the reaction order using pseudo first and pseudo-second order kinetics models. The authors processed the sorption isotherms obtained during the experiments using the Langmuir model. The maximum sorption capacity increased by 3 times compared to the original flax fibre. IR spectroscopy confirmed the improvement of equilibrium and kinetic characteristics of flax fibre occuring as a result of the appearance of new sorption centres in its structure.

Adsorptive potential of apricot (Prunus Armeniaca) stone in the removal of Cr (VI) and Fe (II) ions from Aquatic Systems: Kinetic and isothermal investigations

Biogenic adsorbents have emerged as a promising alternative to the traditional remediation techniques of heavy-metals contaminated water treatment. Using apricot (Prunus Armeniaca) stone as a naturally derived adsorbent, the current study provides a comprehensive analysis of the kinetic and isothermal characteristics associated with Cr (VI) and Fe (II) ion adsorption. The results show that 0.5 mg of the adsorbent removed approximately 90 % of Cr (VI) and Fe (II) ions from 100 ppm solutions within 120 min at 298 K at 300 rpm stirring speed. Equilibrium was attained within 90 to 120 min, with a significant increase in the removal percentage observed in the first 30–40 min for both metals compared to the subsequent 80–90 min. The optimal pH conditions for adsorption were determined to be acidic (pH = 1.5) for Cr (VI) and neutral (pH = 7) for Fe (II). The adsorption kinetics followed a pseudo-second order model, while the isothermal equilibrium data best fit the Freundlich model over the Langmuir model. Moreover, the thermodynamic parameters, including ΔG°, ΔH°, and ΔS°, indicated that the sorption process is spontaneous, feasible, and endothermic. The response surface methodology (RSM) analysis showed a high level of accuracy in predicting the percent removal. These findings illustrate the effectiveness of apricot stone as a low-cost and environmentally conscious adsorbent, contributing to the development of sustainable water treatment technologies.

Fabrication and characterization of PEGylated magnetite nanoparticles for sustained curcumin release: in-vitro study

Abstract A novel approach was adopted to synthesize size-controlled magnetite nanoparticles (MNPs) coated with different molecular weights of polyethylene glycol (PEG), like PEG 750, PEG 2000, and PEG 5000. The drug release kinetics of curcumin (CPMNPs) loaded PEGylated samples were studied. Different techniques used to characterize nanoparticles, like transmission electron microscopy (TEM), x-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The in-vitro studies of curcumin from CPMNPs samples observed a sustained release through kinetics studies from the PMNPs that followed a pseudo-second order reaction. MNPs functionalized with different molecular weights of PEG to make the MNPS biocompatible; moreover, the role of PEG on sustained release of curcumin was also investigated. It was concluded that the particles synthesized at pH-10 coated with PEG of molecular weight 750 exhibited the highest sustained release efficiency of curcumin, i.e., about 98.8%.

Development of the Diffusive Gradient in Thin Film (DGT) Method with CaO/Biochar Binding Agent from Eggshells and Rice Straw Waste for Determining the Concentration of Phosphate

Phosphorus, often found in the form of phosphate in the environment, especially aquatic environments, has been identified as the primary contaminant that causes algae blooms and eutrophication. Phosphate adsorption in the aquatic environment was carried out by comparing the adsorption capabilities of eggshell (CaO), rice straw (BC) and CaO/biochar materials at mass variations of 1:1, 1:2 and 2:1 from the use of eggshell and rice straw waste. Each material was synthesized using ball milling and pyrolysis methods. The adsorption isotherm and kinetics of the material are by the Langmuir adsorption isotherm and are pseudo-second-order (PSO) adsorption kinetics. The CaO/biochar 1:2 material shows the highest phosphate adsorption capacity at pH 12 with a contact time of 24 hours. CaO/biochar 1:2 was applied in the phosphate adsorption process using the Diffusive Gradient in Thin Film method as a binding agent, which acts as an adsorbent. The DGT technique is an in situ sample preparation technique for identifying the presence of phosphate, a labile species. The binding agent material was characterized using FTIR, XRD, and BJH-BET instruments. The success of synthesizing CaO/biochar 1:2 binding gel and ferrihydrite was demonstrated by the appearance of the same adsorption as the diffusive gel using FTIR. The CaO/biochar binding gel demonstrated that it is a better material compared to the ferrihydrite binding gel for phosphate adsorption, achieving CDGT values of 10.1727 mg/L and 2.5959 mg/L at pH 5 and 3, respectively, with a phosphate concentration of 10 mg/L. These findings underscore the potential of CaO/biochar as a more effective material for phosphate removal applications.

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.

Enhanced Hydrophobicity and Oleophilicity of Modified Activated Carbons Derived from Agro-Wastes Biomass for the Removal of Crude Oil from Aqueous Medium

Crude oil spillage has tremendous environmental impacts and poses severe pollution problems worldwide due to the continuous activities and operations in the oil and gas sector. This has resulted in the urgent need for clean-up techniques such as the use of natural adsorbents which is considered a relatively low-cost, readily-available, efficient, eco-friendly, and easy-to-deploy mode of addressing oil spillage due to its high oil sorption capacity/efficiency, high oil selectivity, oleophilic, enduring, reusability and biodegradable properties. Empty palm fruit bunch and coconut coir were used as precursors to produce activated carbons for oil spill remediation. The influence of varying parameters was investigated using a batch experimental procedure resulting in the crude oil adsorption capacity increasing with a corresponding increase in contact time, initial oil concentration, temperature, agitation speed, and particle size but decreasing in adsorbent dosage. The combination of surface morphological modification and hydrophobicity enhancement resulted in significantly improved adsorption capacity for crude oil removal (2710.0 mg/g and 4859.5 mg/g for EPFBAC&amp;lt;SUB&amp;gt;LA&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively), as evidenced by both FTIR and SEM analyses. The experimental isotherm data were analysed using various isotherm models and the best-fitted isotherm model was the Freundlich model with a correlation coefficient (R&amp;lt;sup&amp;gt;2 &amp;lt;/sup&amp;gt;= 0.991 and R&amp;lt;sup&amp;gt;2 &amp;lt;/sup&amp;gt;= 0.999) for EPFB&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively. The kinetic behaviour of the adsorption process was best described by pseudo-second order with R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt; values of 0.970 and 0.999 for EPFBAC&amp;lt;SUB&amp;gt;LA&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively while Boyd model revealed that the adsorption was controlled by an internal transport mechanism and film diffusion was the rate-limiting step. The crude oil adsorption was chemisorption and endothermic owing to the positive enthalpy values (ΔH&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt; = 183.890 KJ/mol for EPFBAC&amp;lt;SUB&amp;gt;L.A &amp;lt;/SUB&amp;gt;and ΔH&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt; = 69.656 KJ/mol for CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt;), the positive value of entropy suggested that the adsorption process was accompanied by an increase in the degree of randomness or disorder at the interface between the adsorbent and the adsorbate. A temperature rise led to a decline in Gibbs energy (ΔG&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt;), suggesting that adsorption became more feasible and spontaneous at higher temperatures and the significant activation energies indicated the existence of a substantial energy barrier that must be overcome to initiate the reaction. The results showed the significant capability of the prepared adsorbents to be used as a low-cost, re-generable and eco-friendly adsorbent in oil spill clean-up and is recommended to exploit its usage on a large scale.