Freundlich Adsorption Isotherm Research Articles

Unlocking the potential of biochar: an iron-phosphorus-based composite modified adsorbent for adsorption of Pb(II) and Cd(II) in aqueous environments and response surface optimization of adsorption conditions.

In this work, iron-phosphorus based composite biochar (FPBC) was prepared by modification with potassium phosphate and iron oxides for the removal of heavy metal ions from single and mixed heavy metal (Pb and Cd) solutions. FTIR and XPS characterization experiments showed that the novel modified biochar had a greater number of surface functional groups compared to the pristine biochar. The maximum adsorption capacities of FPBC for Pb(II) and Cd(II) were 211.66mg·g-1 and 94.08mg·g-1 at 293K. The adsorption of Pb(II) and Cd(II) by FPBC followed the proposed two-step adsorption kinetic model and the Freundlich isothermal adsorption model, suggesting that the mechanism of adsorption of Pb(II) and Cd(II) by FPBC involved chemical adsorption of multiple layers. Mechanistic studies showed that the introduction of -PO4 and -PO3 chemisorbed with Pb(II) and Cd(II), and the introduction of -Fe-O increased the ion exchange with Pb(II) and Cd(II) during the adsorption process and produced precipitates such as Pb3Fe(PO4)3 and Cd5Fe2(P2O7)4. Additionally, the abundant -OH and -COOH groups also participated in the removal of Pb(II) and Cd(II). In addition, FPBC demonstrated strong selective adsorption of Pb(II) in mixed heavy metal solutions. The Response Surface Methodology(RSM) analysis determined the optimal adsorption conditions for FPBC as pH 5.31, temperature 26.01°C, and Pb(II) concentration 306.30mg·L-1 for Pb(II). Similarly, the optimal adsorption conditions for Cd(II) were found to be pH 5.66, temperature 39.34°C, and Cd(II) concentration 267.68mg·L-1. Therefore, FPBC has the potential for application as a composite-modified adsorbent for the adsorption of multiple heavy metal ions.

Enhancing the performance of alumina-pillared clay for phenol removal from water solutions and polyphenol removal from olive mill wastewater: Characterization, kinetics, adsorption performance, and mechanism

An alumina-pillared clay (Al-PILC) has been synthesized and tested for its ability to adsorb phenol from aqueous solutions, and polyphenols from Olive Mill Wastewater (OMW). The synthesis processes were investigated by varying parameters like the Al/clay ratio, with a molar ratio of [OH−]/[Al3+] = 2.4. Various techniques, including XRD, BET, XRF, FTIR, and SEM were used to characterize the resulting solids. The effect of key factors as pH, initial pollutant concentration, and contact time, were examined in order to evaluate the phenol adsorption capacities of raw clay (RC) and optimized Al-PILC10 materials. The specific surface areas of RC and Al-PILC10 were 40 and 127 m2/g, respectively, resulting in increasing the phenol adsorbed quantity from 14.15 mg/g for RC to 30.61 mg/g for Al-PILC10 clays, at pH 2 and 45 °C. Pseudo-second-order kinetics and Freundlich adsorption isotherm were suitable for describing phenol adsorption on both clays. Furthermore, Al-PILC10 exhibits an impressive removal efficiency of 76 % for polyphenols from OMW, in contrast to the 50 % achieved by RC at acidic pH. Furthermore, Al-PILC10 showcased a superior desorption rate and a favorable regeneration capacity of 64 % compared to RC (45 %), even after multiple adsorption-desorption cycles. These findings emphasize the potential of pillared clay as a cost-effective adsorbent for the efficient removal of phenol and polyphenols from wastewater.

Ruthenium sorption onto Fe3O4@MnO2: equilibrium, kinetic and thermodynamic study

Core–shell magnetic adsorbent Fe3O4@MnO2 was prepared and successfully used to ruthenium adsorption from aqueous solutions with 98% efficiency. The adsorption isotherms, kinetic and thermodynamic parameters for Ru(III) sorption onto Fe3O4@MnO2 were studied via a batch adsorption system. Adsorption isotherm models such as: Langmuir, Freundlich and Temkin were tested while the kinetic adsorption data were analyzed by pseudo-first order, pseudo-second order, and Weber-Morris models. It has been found that the adsorption process of Ru(III) onto Fe3O4@MnO2 can be describe by a Freundlich model whereas mechanism of sorption is presented better by kinetic Weber–Morris model. Freundlich adsorption isotherm constant is equal Kf = 30.62 mg/g and heterogenity factor n = 3.58. Sorption rate constant is k3 = 0.288 mg/(g·min1/2) and intraparticle diffusion rate constant C = 0.174 mg/g. Thermodynamic parameters such as free Gibb’s energy change (ΔG°), enthalpy change (ΔH°), entropy change (ΔS°) and energy activation Ea were determined. Calculated value of activation energy is equal 25.75 kJ/mol. The adsorption process of Ru(III) was found to be both spontaneous and thermodynamically preferable.

The polyelectrolyte as corrosion inhibitor for the aluminum anode in alkaline-based primary battery: A comparative study with its monomer

In this work, the corrosion inhibition effect of the polyelectrolyte, poly(diallyl dimethylammonium chloride) (PDDA), as an additive in the alkaline Al-air battery is described and compared with the monomer dimethyl diallyl ammonium chloride (DMDAAC). Electrochemical measurement and morphology analysis are employed to characterize the inhibition effects of the additives. Additionally, the discharge characteristics of the battery are explored, and the capacity density is derived. These results demonstrate that the polymer additive suppresses Al samples' corrosion process more effectively than DMDAAC. The adsorption mechanism is proposed based on the Freundlich adsorption isotherm theory and quantum mechanical calculation.

Adsorption of Thorium (IV) from Aqueous Solutions Using Mesoporous TiO2: Kinetics, Isotherm and Thermodynamics

Thorium is considered as a promising resource for the production of nuclear power, with its abundance in the Earth's crust offering potential for sustainable energy generation to fulfill upcoming energy needs. As a fertile material, thorium has the capability to be converted into fissile uranium-233, which is essential for sustaining nuclear chain reactions. Therefore, the extraction of thorium from the Earth's crust is imperative for its utilization as fuel in nuclear reactors. This study presents the synthesis of Titanium dioxide with a mesoporous structure using the solvothermal method for extracting Th(IV) from aqueous solutions. Batch adsorption experiments were carried out to evaluate the impact of solution pH, adsorption kinetics, adsorbent dosage, initial Th(IV) concentration, and temperature. The adsorption process is influenced by the pH, showing a maximum adsorption capacity of 101.4 mg per gram of mesoporous TiO2 adsorbent (MTA) at an initial Th(IV) concentration of 400 mg L−1 and pH 4.0. Results indicate a significant correlation with the pseudo-second-order and Freundlich adsorption isotherm models. Temperature-dependent investigations revealed that the adsorption of Th(IV) is spontaneous at room temperature and increases with higher temperatures (endothermic process). Moreover, the study highlights the rapid kinetics of Th(IV) adsorption by MTA, making it a favorable choice for upscaling the extraction process of Th(IV). In conclusion, the results suggest MTA as a promising adsorbent for the removal of Th(IV) from aqueous solutions.

Exploring the influence of invasive weed biochar on the sorption and dissipation dynamics of imazethapyr in sandy loam soil.

The management of invasive weeds on both arable and non-arable land is a vast challenge. Converting these invasive weeds into biochar and using them to control the fate of herbicides in soil could be an effective strategy within the concept of turning waste into a wealth product. In this study, the fate of imazethapyr (IMZ), a commonly used herbicide in various crops, was investigated by introducing such weeds as biochar, i.e., Parthenium hysterophorus (PB) and Lantana camara (LB) in sandy loam soil. In terms of kinetics, the pseudo-second order (PSO) model provided the best fit for both biochar-mixed soils. More IMZ was sorbed onto LB-mixed soil compared to PB-mixed soil. When compared to the control (no biochar), both PB and LB biochars (at concentrations of 0.2% and 0.5%) increased IMZ adsorption, although the extent of this effect varied depending on the dosage and type of biochar. The Freundlich adsorption isotherm provided a satisfactory explanation for IMZ adsorption in soil/soil mixed with biochar, with the adsorption process exhibiting high nonlinearity. The values of Gibb's free energy change (ΔG) were negative for both adsorption and desorption in soil/soil mixed with biochar, indicating that sorption was exothermic and spontaneous. Both types of biochar significantly affect IMZ dissipation, with higher degradation observed in LB-amended soil compared to PB-amended soil. Hence, the findings suggest that the preparation of biochar from invasive weeds and its utilization for managing the fate of herbicides can effectively reduce the residual toxicity of IMZ in treated agroecosystems in tropical and subtropical regions.

Measurement of neuropeptide Y in aptamer-modified planar electrodes

Electrochemical impedance spectroscopy (EIS) is a powerful technique for studying the interaction at electrode/solution interfaces. The adoption of EIS for obtaining analytical signals in biosensors based on aptamers is gaining popularity because of its advantageous characteristics for molecular recognition. Neuropeptide Y (NPY), the most abundant neuropeptide in the body, plays a crucial role with its stress-relieving properties. Quantitative measurement of NPY is imperative for understanding its role in these and other biological processes. Although aptamer-modified electrodes for NPY detection using EIS present a promising alternative, the correlation between the data obtained and the adsorption process on the electrodes is not fully understood. Various studies utilize the change in charge transfer resistance when employing an active redox label. In contrast, label-free measurement relies on changes in capacitance. To address these challenges, we focused on the interaction between aptamer-modified planar electrodes and their target, NPY. We proposed utilizing −ω*Zimag as the analytical signal, which facilitated the analysis of the adsorption process using an analogous Langmuir isotherm equation. This approach differs from implantable microelectrodes, which adhere to the Freundlich adsorption isotherm. Notably, our method obviates the need for a redox label and enables the detection of NPY at concentrations as low as 20 pg/mL. This methodology demonstrated exceptional selectivity, exhibiting a signal difference of over 20-to-1 against potential interfering molecules.

Untapped potential of food waste derived biochar for the removal of heavy metals from wastewater

The presence of heavy metals in water pose a serious threat to both public and environmental health. However, the advances in the application of low cost biochar based adsorbent synthesize from various feedstocks plays an effective role in the of removal heavy metals from water. This study implies the introduction of novel method of converting food waste (FW) to biochar through pyrolysis, examine its physiochemical characteristics, and investigate its adsorption potential for the removal of heavy metals from water. The results revealed that biochar yield decreased from 18.4 % to 14.31 % with increase in pyrolysis temperature from 350 to 550 °C. Likewise, increase in the pyrolysis temperature also resulted in the increase in the ash content from 39.87 % to 42.05 % thus transforming the biochar into alkaline nature (pH 10.17). The structural and chemical compositions of biochar produced at various temperatures (350, 450, and 550 °C) showed a wide range of mineralogical composition, and changes in the concentration of surface functional groups. Similarly, the adsorption potential showed that all the produced biochar effectively removed the selected heavy metals from wastewater. However a slightly high removal capacity was observed for biochar produced at 550 °C that was credited to the alkaline nature, negatively charged biochar active sites due to O-containing functional groups and swelling behavior. The results also showed that the maximum adsorption was recorded at pH 8 at adsorbent dose of 2.5 g L−1 with the contact time of 120 min. To express the adsorption equilibrium, the results were subjected to Langmuir and Freundlich isotherms and correlation coefficient implies that the adsorption process follows the Freundlich adsorption isotherm. The findings of this study suggest the suitability of the novel FW derived biochar as an effective and low cost adsorbent for the removal of heavy metals form wastewater.

Preparation of Activated Biocarbons from Cones and their Potential Application for Adsorption of Antibiotics (Tetracycline).

The pine cones (PC), spruce cones (SC) and fir cones (FC) were used for biocarbons preparation. Chemical activation with sodium hydroxide was applied to prepare activated biocarbons. All the materials under investigation were characterized by the N2 adsorption, scanning electron microscopy (SEM), elemental analysis (CHNS), infrared spectroscopy (ATR FT-IR), and the Boehm's titration method. Moreover, pHpzc (the point of zero charge) was determined. It was shown that cones are a good, cheap precursor from which biocarbons with a developed porous structure, characterized by good adsorption properties, can be obtained. All the obtained adsorbents are characterized mainly by a microporous structure. Moreover, they contain both acidic and basic surface functional groups (acidic ones prevail over basic ones). The tested activated biocarbons have large specific surface area values ranging from 578 to 1182 m2 g-1. The efficacy of selected materials in the adsorption of an essential contaminant of increasing concern, tetracycline (TC), was investigated. The experimental data were described using the Langmuir and Freundlich adsorption isotherm models. The maximum adsorption capacity of the tested biocarbons ranges from 200 to 392 mg g-1. Thermodynamic studies proved that adsorption is a spontaneous and endothermic process. In summary, economical and environmentally friendly adsorbents were obtained.

Application of ANN, hypothesis testing and statistics to the adsorptive removal of toxic dye by nanocomposite

Statistics can be used in a variety of ways to present, compute, and critically analyze experimental data. To determine the significance and validity of the experimental data, a variety of statistical tests are used. Using a synthesized CoO/NiO/MnO2 Nanocomposite, the present study used adsorption to remove the dye Bromophenol Blue (BPB) from a contaminated aqueous solution. In order to (a) determine the optimal pH of the solution, (b) confirm the experiment's success, and (c) investigate the effect of adsorbent dose on BPB dye removal from aqueous solutions. The experimental data were statistically analyzed through hypothesis testing using the t-test, paired t-test, and Chi-square test. The null hypothesis that the optimal pH value is 7 is accepted since tobserved (−1.979)<ttabulated (−2.262). Since χ2observed (1.052)< χ2tabulated (3.841), null hypothesis that the higher adsorbent dose helps in higher % removal of dye is accepted. Both the obtained Freundlich adsorption isotherm and the Langmuir isotherm's R2 values, which were both close to 1, indicate that the isotherms are favorable. Karl Pearson's relationship coefficient values for Langmuir and Freundlich adsorption isotherms found to be 0.9693 and 0.9994 respectively, which show a more significant level of connection between's the factors. The ANN model predicted adsorption percentage with regression value R is 0.996. ANN model result predict 99.60 % BPB dye adsorption using optimized parametric conditions. The ANN model produced values that were more precise, reliable, and reproducible, demonstrating its superiority.

A graphene oxide based composite granule for methylene blue separation from aqueous solution: Adsorption, kinetics and thermodynamic studies

Graphene oxide and chitosan composite material using as a high-efficiency and low-cost granular adsorbent for methylene blue removal was fabricated via self-assembling method. The effects of pH value, contact time, initial concentration, adsorbent dose, temperature, and recyclic stability on the adsorption performance of methylene blue in aqueous solution were investigated in detail. Desorption process with the effects of solvents, contact time, and temperature were also conducted carefully in this study. The adsorption kinetics and adsorption isotherm of dye adsorption process showed that dye adsorption process was fitted to the pseudo-second-order kinetic model and the Freundlich adsorption isotherm, indicating a physical adsorption process with multilayer adsorption. The intra-particle diffusion model indicated that the dye adsorption by the granular adsorbent was strongly happened during the first 4 h. The thermodynamic study showed that the adsorption was a spontaneous and exothermic process and dye ions were condensed onto the surface of adsorbent. The maximum adsorption capacity of dye on the granular adsorbent was calculated as 951.35 mg/g and the adsorbent could maintain its adsorption performance after six cycles. In general, this study provided an efficient, cost-effective, and recyclable the granular adsorbent for dye separation from aqueous solution.

The removal of Sb from mine wastewater using biosynthesized Fe-Mn nanoparticles: Function and mechanism

Antimony (Sb) in mine wastewater poses a serious threat to surrounding ecosystems. In this study, biosynthesized iron-manganese nanoparticles (Fe-Mn NPs) were devised to remove Sb species. The resultant removal efficiencies were 100% for Sb(III) and 82.6% for Sb(V) utilizing a Sb(III) and Sb(V) concentration of 1mg·L-1. To understand the removal process, Fe-Mn NPs before and after exposure to Sb species were characterized by various advanced techniques, which indicated that while both Sb(III) and Sb(V) were adsorbed onto the surface of Fe-Mn NPs, Sb(III) was also partly oxidized to Sb(V). Furthermore, removal of both Sb(III) and Sb(V) followed pseudo-second-order kinetics and best fit the Freundlich adsorption isotherm model, suggesting that the removal process involved non-homogeneous chemisorption. These studies provided the evidence for an adsorption and oxidation mechanism for Sb(III) removal and an adsorption-dominated mechanism for Sb(V) removal by Fe-Mn NPs. When the produced Fe-Mn NPs were applied to remove Sb from mine wastewater, 92.7% removal was attained, demonstrating the significant practical potential of these nanoparticles to Sb species from mine wastewaters. This study provides novel insights for future exploration for Sb removal from mine wastewaters.

Study of The Inhibition Corrosion of Aluminum Metal Using Peppermint Oil in An Acidic Medium

This study included the study of the efficiency of peppermint oil inhibition of aluminum corrosion in acidic medium HCl at concentrations (0.5, 1, 1.5, 2 M) on the corrosion rate in the presence and absence of the inhibitor peppermint oil at different concentrations (1000, 2000, 3000, 4000 ppm).In order to study the effect of changing the temperature (303, 313, 323, 333 K) on the corrosion rate in the absence and presence of the inhibitor, different concentrations of the inhibitor were chosen in addition to the acid concentration (1M). The experiments were carried out using the weight loss method to calculate the erosion rate. The expected heat of adsorption enthalpy was (-29.913 KJ/mol), with a negative sign indicates that the process is exothermic. The value of the free energy of adsorption ranged from (11.086-15.067 KJ/mol. (The results showed that Freundlich adsorption isotherm equation is the best fit to examine the adsorption process, also a scanning electron microscope. Showed the surface of aluminum before and after corrosion according to the results of the study, it was found that the used inhibitor reduces corrosion in acidic media. Its anti-corrosion efficacy also improves with increasing inhibitor concentration and with decreasing temperature.

Modified biochar activated by traditional Chinese medicine extract and its removal of tetracycline

Traditional Chinese medicine (TCM) has been widely used during the outbreak of Covid-19 in the past few years, causing waste of resources and environmental pollution. This paper will convert TCM into porous carbon-based materials through pyrolysis technology, and then combine it with TCM extract activator to synthesize a new type of adsorbent. The two main ingredients of Chinese patent medicine “Lianhua Qingwen Capsules”, Honeysuckle and Forsythia suspensa, will be used as raw materials. After the two herbs are crushed, the leachate is extracted, and the remaining residue is collected. The dried residue is activated and carbonized at high temperature to generate biochar. Further, the biochar will be soaked in TCM extraction liquid to load active ingredients. The adsorption mechanism of tetracycline (TC) by TCM biochar was explored based on the adsorption kinetics and adsorption isotherm fitting results. The microstructure, surface functional groups and crystal structure of TCM biochar will reveal the material properties of the adsorbent. The results show that compared with biochar without extract activation, the adsorption effect of combined biochar (BC-C) with the proportion of “Lianhua Qingwen Capsules” is greatly improved. BC-C has richer surface functional groups through TCM extract loading, which provides superior TC adsorption capacity (36.92 mg/g). The adsorption process of TC by TCM biochar follows the pseudo-second-order adsorption kinetic model and Freundlich adsorption isotherm model. The adsorption mechanism mainly involves pore filling, hydrogen bonding, electrostatic interaction and π-π interaction.

Hybrid Banana Pseudo Stem biochar- poly (N-hydroxyethylacrylamide) hydrogel and its magnetic nanocomposite for effective remediation of dye from wastewater

A hybrid hydrogel based on Banana Pseudo Stem, an agricultural waste material, has been developed as an adsorbent for use in wastewater treatment. The Biochar obtained from Banana Pseudo Stem was modified by graft copolymerization with N-hydroxyethylacrylamide (HEAAm). The graft copolymer was made by microwave irradiation of an aqueous mixture containing BPSBC, N-hydroxyethylacrylamide (HEAAm), N,N-methylenebisacrylamide (MBA), and potassium peroxodisulphate (KPS). The magnetite (Fe3O4) nanoparticles have been incorporated into the gel by in-situ diffusion of Fe2+ and Fe3+ followed by a reaction with ammonia solution. FTIR, SEM, EDS, TGA, VSM, BET, and XRD techniques were used to characterize the gel and its nanocomposite. The swelling process appeared to be a second-order kinetic process and the mechanism of water transport is found to be non-Fickian. The hybrid gel and nanocomposite were evaluated for the adsorptive removal of cationic dyes using Methylene Blue (MB) and Crystal Violet (CV) as model dyes. The adsorption capacities of the graft copolymer gel for MB and CV were 200 mg g−1 and 183 mg g−1 respectively. A considerable increase in adsorption capacities was observed in nanocomposite formation, with adsorption capacity values of 235 and 202 mg g−1 for MB and CV respectively. The pseudo-second-order kinetic model and Freundlich adsorption isotherm model provide the best fit of the dye sorption data. Thermodynamic studies revealed adsorption to be a spontaneous and endothermic process. Effective desorption under acidic conditions illustrated the possibility of reuse of the developed adsorbent materials in repeated cycles during the wastewater treatment process.

Enhancement of CO2 adsorption performance with the chitosan-modified activated carbon by different methods

Carbon dioxide (CO2) has almost become synonymous with greenhouse gases. Neither improvement of energy efficiency nor the application of alternative energy can reduce the concentration of CO2 to the allowable concentration. Therefore, CO2 must be captured to prevent its escape into the atmosphere. CO2 is commonly adsorbed by activated carbon because of the good affinity between them. In this study, to enhance the CO2 adsorption performance of this material, activated carbon was modified by two ways, synthesis and grafting with chitosan, to examine how the adsorption performance was affected by the different modifications. The experimental results showed that the adsorption performances of activated carbon with grafted chitosan and synthesized with chitosan were better than that of activated carbon. Although the nitrogen content was higher in the activated carbon synthesized with chitosan than in the carbon grafted with chitosan, the adsorption enhancements were similar due to the reduced surface area of the former. In addition, the results of the multi adsorption-desorption processes showed that the adsorption performance of the activated carbon grafted with chitosan slightly decreased, while that of the activated carbon synthesized with chitosan was almost unchanged. As the heterogeneous adsorption was modeled well by the Toth adsorption isotherm model, this isotherm model was used to model the experimental data for comparison with the Freundlich adsorption isotherm model. The average deviation of adsorption uptake fitted by the Toth adsorption isotherm model was about 3.07%, in comparison with 12.71% fitted by the Freundlich adsorption isotherm model.

A hybrid electrocoagulation-biocomposite adsorption system for the decolourization of dye wastewater

Among the various methods for the removal of azo dye, electrocoagulation is recognized to be highly efficient. However, the process is associated with high operation and maintenance cost, which demands the need for reducing the electrolysis time without compromising the performance efficiency. This can be achieved by adopting hybrid electrocoagulation process with a low-cost but effective process, such as adsorption. The study investigated the performance of a hybrid electrocoagulation-biocomposite system (H-EC-BC) for removing methyl orange dye. Firstly, the operating parameters of electrocoagulation process were optimized and a removal efficiency of 99% has been attained using Fe-SS electrodes at a pH of 6 for a reaction time of 30 min. The performance of EC process was found to be decreasing with increase in dye concentration. Secondly, biocomposite was synthesized from Psidium guajava leaves and characterized using SEM, FTIR, EDAX, and XRD analyses. The results suggested that it is having a porous nature and cellulose crystal structure and confirmed the presence of chemical elements such as carbon (65.2%), oxygen (29.1%) as primary with Fe, Cl, Na and Ca as secondary elements. The performance of the biocomposite was evaluated for the dye adsorption using spectrophotometric methods. Various operating parameters were optimized using experimental methods and a maximum removal efficiency of 65% was achieved at a pH of 6, dosage of 5 g/L and an adsorption contact time of 120 min. The maximum efficiency (92.78%) was obtained with Fe-SS electrodes and KCl as a sustaining electrolyte under acidic circumstances (pH 6). The biocomposite was observed to be more efficient for higher dye concentration. Langmuir and Freundlich adsorption isotherms were fitted with the experimental results with R2 values as 0.926 and 0.980 respectively. The adsorption kinetics were described using Pseudo-first and Pseudo-second order models, wherein Pseudo-second order model fits the experimental results with R2 value of 0.999. The energy consumption of electrocoagulation (EC) process in the hybrid H-EC-BC system was compared to that of a standard EC process. The results demonstrated that the hybrid system is approximately 7 times more energy efficient than the conventional process, thereby implicating its adaptability for field application.

NaY zeolite synthesis from rice husk ash for Chromium(VI) ion adsorption

NaY zeolite in this study is novelly synthesized from rice husk ash with a one-stage process instead of passing the solid silica recovery process as usual. NaY zeolite applies to assess adsorption ability of chromium(VI) ions in water with varying key factors. The as-synthesized zeolite is characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscope, specific surface area analysis and inductively coupled plasma mass spectrometry with optical emission spectroscopy. As a result, the optimal conditions for silica extraction are at 90oC with a NaOH concentration of 4 M for 4 h with recovery efficiency 87.5%. NaY zeolite is successfully synthesized with Si/Al ratio of 10, aging time of 24 h and crystallization time of 24 h with synthesis yield of 31.25% and crystallinity of 96%. The optimal conditions for the chromium(VI) adsorption in aqueous solution are at pH 2.0, adsorption time of 120 min, initial concentration of 20 mg/L with an adsorbent mass of 0.1 g. The kinetics and adsorption isotherms show a good agreement with pseudo-second order and Freundlich adsorption isotherm model. NaY zeolite is synthesized via environmentally friendly approach with time and energy savings and shows its high adsorb-ability of chromium(VI) in water.

EXPLORING THE POTENTIAL OF AGRICULTURAL WASTE AS NATURAL RESOURCE-BASED ADSORBENTS FOR METHYLENE BLUE REMOVAL

Excessive agricultural waste in the agricultural industry leads to various forms of pollution, including water pollution. To address this issue, there's a growing interest in finding alternative methods. One approach is to utilize agricultural waste as natural resource-based adsorbents to eliminate contaminants, such as the case of methylene blue (MB) in this study. The study specifically focuses on using rice husk (RH) from a local rice mill in Perlis, Malaysia, to absorb methylene blue. The structure of rice husk, characterized by scanning electron microscopy (SEM), reveals a coarser and more compact outer area, contributing to its absorption capacity for methylene blue. The study on rice husk involves three main aspects: contact time, adsorbent dosage, and dye concentration. The removal percentage of MB increased as the three studied adsorption parameters increased. The adsorption data were analyzed using Langmuir and Freundlich adsorption isotherms, with the the Freundlich Isotherms were found to be more suitable based on higher coefficient of correlation (R2) values compared to Langmuir. The pseudo-second-order kinetics model demonstrated a higher R2 value (1.00) compared to the pseudo-first-order model (0.747). The results indicate promising potential for addressing pollution through sustainable means and provide insights into the adsorption process under varying conditions.

Removal of Congo red dye from industrial effluents using metal oxide-clay nanocomposites: Insight into adsorption and precipitation mechanisms

The efficacy of magnesium oxide (MgO)-bentonite clay nanocomposite particles (MgO nanoparticles embedded in powdered bentonite clay) for water and wastewater treatment applications is examined herein. Congo red (CR), a widely used azo dye, was used as the model contaminant. For CR concentrations ≤120 mg/L, the optimum nanocomposite dosage was ≤1 g/L, achieving CR removal ≥99% for contact times (mixing durations) ≤10 min, whereas temperature and pH had no significant effect on the treatment process. The removal of CR dye followed the pseudo-second-order model than the first order model. Furthermore, adsorption isotherms followed the Langmuir adsorption isotherm rather than the Freundlich adsorption isotherm (R2 ≥ 0.99), hence confirming monolayer homogenous adsorption. The surface morphological and physicochemical characteristics of the nanocomposite were also identified, and results suggest that CR removal was governed by electrostatic attraction between the protonated hydroxyl groups (i.e., -OH2+), embedded on the nanocomposite surface, and the negatively charged –SO3-groups of the CR dye. When used for the treatment of real printing ink wastewater, CR was practically removed (⁓100%), whereas for real printing and dyeing wastewater (PDW), a more challenging effluent that also contains salts and other contaminants, CR removal was ≥80%. Overall, the produced MgO-bentonite clay nanocomposite hold great promise for sustainable CR removal, a typical contaminant that is released by many industries including printing, tannery and textile, paper, plastic, and paint and coatings.