Adsorption Kinetic Models Research Articles

Refinement of a kinetic adsorption model through Artificial Intelligence

The adsorption process involves capturing contaminants at active sites on adsorbent materials. Its economic efficiency and simplicity distinguish it as a preferred option amidst concerns about anthropogenic pollution. Traditional kinetic models present challenges in fitting nonlinear behaviors of porous materials, prompting the exploration of alternative approaches. Machine learning has a wide range of applications in various fields, including environmental engineering. These models possess generalization capabilities and are used as predictive tools, but they can lead to undesired behaviors if the system is complex and the model fails to capture this complexity. A novel methodology is proposed where the calibration of traditional models is studied using a machine learning model for adsorption kinetics, with hexavalent chromium as the adsorbate and activated carbon as the adsorbent. Furthermore, the technique of adding synthetic data to influence the model's capacity is studied, considering whether it leads to overfitting.Traditional models include pseudo first and second order kinetics, while multilayer perceptron is used as the machine learning model. The models obtained through the proposed methodology exhibit significant performance compared to traditional models. Additionally, an improved interpretability in their behavior compared to using only an artificial intelligence model is observed. Calibration ensures physical interpretation while enhancing generalization. The incorporation of synthetic data into the artificial intelligence model resulted in overfitting, subsequent ensemble methods effectively leveraged this, reducing bias related errors. The impact of synthetic data on calibration has demonstrated favorable outcomes.

Kinetic adsorption and isotherm models of nickel

The study investigated the adsorption capacity of Pinus halepensis Mill biomass (PHM) that has been modified to remove nickel (II) from aqueous solutions. The underwent chemical modification using zinc chloride (0.1N) to produce activated carbon. The resultant products were analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. Several variables were taken into account to achieve optimal adsorption conditions. These factors include the duration of agitation, the starting concentration of copper, and the pH level. Consequently, the highest level of efficiency was obtained at 90 mg/g when equilibrium was established after 120 minutes. The pseudo-second-order kinetic model offers a more appropriate characterization of the adsorption kinetics. Nickel adsorption adheres to the principles of the Langmuir and Freundlich isotherms. The Langmuir isotherm model produces the most favorable parameters. The adsorption capacity increased with the elevation of the initial concentration (from 1000 to 400mg/l) employed in this work at a neutral pH and 25°C in temperature.

Synthesis of Activated Carbon from Dragon Fruit Peel for Adsorption of Methyl Blue

In this study, activated carbon from dragon fruit peel was synthesized and applied for its ability to adsorb organic pigments in water. The results obtained from the SEM and FTIR analyzes revealed the presence of the characteristic functional groups of activated carbon. The adsorption capacity of synthetic activated carbon was evaluated against methylene blue dye. This study also evaluated factors affecting the adsorption process, including time, content, temperature, concentration, and solution pH. The optimal adsorption conditions were recorded at pH 6, concentration 95 mg/L, time 43 min, and temperature 30 °C. At optimal adsorption conditions, the adsorption capacity predicted from the model is said to be 54.12 mg/g with an efficiency of 27.5%. The experimental data of the study were evaluated using adsorption kinetic models and adsorption isotherm models of the material. The results showed that the activated carbon material from dragon fruit peel is a potential material in the application for adsorbing pollutant dyes in wastewater.

Adsorption equilibria and kinetics of CO2 and N2 on silica-alumina gels for reducing gas production by CO2 removal from iron flue gases

In industrial fields, hydrogen-containing flue gases generally contain a certain amount of CO2 and N2. After removing CO2, the raffinate gases can be used in various applications to mitigate carbon emissions. Furthermore, the concentrated CO2-rich extract contributes to efficient CO2 capture. Silica-alumina gel can be a high potential adsorbent because of its high CO2 adsorption capacity and energy-saving desorption. Three different silica-alumina gels with different amounts of alumina (FJ, KD, and WS) were compared to study the impact of the alumina content on the adsorption characteristics. The adsorption behaviors of CO2 and N2 were measured at 293K, 308K, and 323K at pressures up to 1000 kPa. The isotherms correlated with the dual-site Langmuir model, showing that the adsorption capacity for CO2 was much higher than that for N2 across all the adsorbents. The surface areas and adsorption capacities followed the opposite order of alumina content: FJ > KD > WS. However, the difference intervals in the isotherms did not align consistently with the alumina content, but the micropore volume changed by alumina contributed highly to the adsorption capacity. In the adsorption kinetic analysis, the diffusional time constants and kinetic parameters in a non-isothermal adsorption kinetic model showed minor dependence on pressure and temperature. The adsorption rate was higher for N2 than for CO2. It increased with alumina content, following the order WS > KD >> FJ. The results contribute to the establishment of guidelines for the selection of silica-alumina gel and the design of the adsorption process.

Scalable, high flux of electrospun nanofibers membrane for rapid adsorption-reduction synergistic removal of Cr(VI) ions in wastewater

Trade-off between flux and reject rate is a long-standing shortcoming of membrane separation for heavy metal ions from wastewater. Herein, we design and develop a scalable, high flux of polyethyleneimine/amidoxime modified polyacrylonitrile (PEI/AOPAN) composite nanofibers membrane via using needle less electro-spun and chemical modification strategies. Subsequently, the prepared nanofibers membrane was used as a membrane separation material to rapidly and efficiently remove Cr(VI) ions from wastewater through the synergistic effect of adsorption-reduction. The result indicated that the scalable membrane was manufactured by needle free electrospinning and amine oxime modification process has the characteristics of uniform fiber diameter (315 nm), excellent hydrophilicity, good acid and alkali resistance stability, and excellent mechanical properties. During the dynamic separation process, the membrane can rapidly and efficiently remove Cr(VI) ions in wastewater (100 mg L−1), which has a flux of up to 1146 L·m−1·h−1 and a retention rate of 99.53 % under pressure conditions of 0.08 MPa. The process of Cr(VI) ions removal by this membrane follows a pseudo first-order adsorption kinetics model and Langmuir adsorption isotherm model. This work confirms the feasibility of porous membrane adsorption with high capacity, and provides the possibility of adsorptive membranes for heavy metal ions from wastewater.

Design of alkali metal oxide adsorbent for direct air capture: Identification of physicochemical adsorption and analysis of regeneration mechanism

Direct air capture (DAC) represents an advanced negative carbon emission technology, with the key being high-performance CO2 adsorbents. First, this work carefully identifies CO2 physisorption and chemisorption by CaO/HcATP (CaO loaded on acid-modified attapulgite) as DAC adsorbent. The chemisorption of amorphous "CaO" plays a crucial role in both the adsorption capacity and rate, with contributions of 66.8 % and 50.85 %, respectively. The adsorption capacity of CaO/HcATP is only 212.4 ± 25.7 µmol/g via the simple CO2 physisorption and improved by 426.7 µmol/g owning to the chemisorption of amorphous CaO. Second, the concentration of silanol groups on CaO/HcATP plays a pivotal role in the adsorption process. The concentration of silanol groups decreases to 3.85 OH/nm2 after undergoing 30 cycles of adsorption-desorption. Then it increases to 9.54 OH/nm2 by adsorbing the moisture in the air, resulting in a recovered adsorption capacity of 90.7 %. Furthermore, the pseudo-first-order adsorption kinetics model effectively predicted the experimental results. Finally, the dual loop of CO2 capture and regeneration is summarized using the CaO/HcATP as DAC adsorbent. The amorphous "CaO" interacts with the surface silanol of HcATP, synergistically capturing CO2 in the form of "CaO···CO2", which reduces desorption energy consumption. The wetting property of HcATP contributes to the regeneration of CaO/HcATP. This work contributes to establishing fundamental principles for designing cost-effective DAC adsorbents.

Evaluation of ZnO/NiO/kaolin nanocomposite as a sorbent/photocatalyst in hybrid water remediation process

The colored effluents causing environmental pollution pose a threat to the world. This study aims to assess the effectiveness of nickel oxide/zinc oxide/kaolin nanocomposite (NiO/ZnO/Ka) in removing methylene blue (MB) from water. Furthermore, it aims to examine the impact of synergetic adsorption/photocatalytic degradation (APCD) on the MB adsorption capacity as well as the suitability of the nonlinear adsorption isotherm and kinetic modeling in analyzing the process. The composites ZnO/Ka and NiO/ZnO/Ka were synthesized by the sol–gel method and were characterized by X-ray diffraction, Fourier transform infra-red, field emission scanning electron microscopy, and Brunauer–Emmett–Teller. The impacts of various parameters, such as pH, initial concentration of MB, dose, ionic strength, and temperature, on MB removal were studied using adsorption and APCD. The results showed that ZnO/Ka had the maximum adsorption capacity of MB (39.31 mg/g) and the maximum removal (78.61%) under optimal conditions of pH 10, clay dosage of 0.1 g/25 mL, initial concentration of MB 200 mg/L, contact time of 15 min, and 298 K, while NiO/ZnO/Ka showed the maximum adsorption capacity of MB (40.88 mg/g) and maximum removal (83.74%) at pH 7. It was also noticed that Temkin and Fritz–Schlunder models are the best isotherm models, with the highest R2 (1 and 0.842) for ZnO/Ka and NiO/ZnO/Ka, respectively. Moreover, the data of adsorption and photodegradation of MB onto ZnO/Ka and NiO/ZnO/Ka were revealed to follow pseudo-first-order and Avrami kinetic models with R2 (0.897) for ZnO/Ka and (0.986) for NiO/ZnO/Ka. Overall, NiO/ZnO/Ka showed better removal of MB than ZnO/Ka, and the hybrid process (photodegradation process after adsorption) enhanced the overall efficiency of MB removal than adsorption alone.

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

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

Adsorption potential of spherical ZnO particles for sufficient antibiotic removal: isotherm, kinetic and thermodynamics

Due to the improvements of pharmaceutical industry, tetracycline (TC) is commonly detected in natural water environments, resulting in significant adverse impacts on living species. In this study, the TC adsorption over commercial spherical zinc oxide (ZnO) samples was systematically examined by considering adsorption isotherm models, kinetic model and thermodynamic behavior. The Langmuir kinetic model displayed the highest correlation coefficient (R2 = 0.97) with a maximum adsorption capacity of 86.35 mg/g. According to the results of the kinetic studies, the adsorption could be driven by both the bulk transfer of adsorbate molecules towards the adsorbent surface within the solution and chemisorption on the surface and inside the pores. In addition, the TC adsorption on the ZnO particles promoted by increasing temperature. The commercial spherical zinc oxide can be considered as a sustainable strategy to eliminate the emerging toxic contaminant of tetracycline.

Kinetic Studies on MB Adsorption by Graphene like Material from Coconut Shell Charcoal

Coconut shell (CS) activated carbon is widely used for water purification, but its adsorption capacity is inferior compare to graphene oxide (GO). GO has oxygen functional groups so it can effectively bind pollutants like methylene blue (MB). In this study we synthesized graphene-like material from CS charcoal using the modified Hummers method by varying its oxidation times. The XRD decomposition results for H-CS3.2 show a structural composition similar to GO material. The diffraction peak at 10.7° (3.04%) falls within GO's characteristic range of 8°-11°, supported by a Raman ID/IG ratio of 0.95. In contrast, H-CS3.1 material does not exhibit GO's structural composition, with a diffraction peak at 13.9° (1.09%). An increasing of oxidation time, enhanced adsorption capacity in the equilibrium state of H-CS3.2 (22.368 mg/g) surpassing H-CS3.1 (17.079 mg/g). The heightened adsorption was linked to an increased O/C ratio or higher % of atomic oxygen (0.04 for H-CS3.1 and 0.17 for H-CS3.2). The pseudo second-order Ho (PSO) adsorption kinetic model demonstrated the adsorption mechanism, with active sites (oxygen functional groups) such as carbonyl (C = O) and epoxy (C – O) at basal plane carbon. Steric hindrance caused by hydroxyl functional groups (C – OH) led to a reduction in π-π interactions and decreased adsorption ability of the H-CS3.1 material. Desorption of H-CS3.1 material was influenced by MB detachment through interface diffusion.

Kinetics of Cd adsorption by biochar, activated carbon, and zeolite in some calcareous soils

AbstractDifferent methods have developed to reduce the risks of potentially toxic elements in contaminated soils. Among them, adsorption is one of the most important and effective strategies. In this research, kinetics of Cd adsorption by biochar, activated carbon, and zeolite in some calcareous soils were investigated. A factorial experiment was conducted based on a completely randomized design with three replications. The factors included three types of adsorbents (sunflower's biochar, activated carbon, and zeolite), four levels of Cd (0, 20, 50, and 100 mg/L as Cd (NO3)2), and three soil samples, differing in their cation exchange capacity, soil organic matter, and calcium carbonate equivalent. Batch experiments were carried out to evaluate Cd adsorption isotherms and kinetic models. Furthermore, the effect of adsorbent dosage, contact time, and initial pH on the adsorption efficiency was examined. Optimizing studies revealed that the best pH for Cd adsorption was 5, while the optimal equilibrium time was achieved at 24 h. The results showed that the Freundlich model fitted to the experimental data slightly better than the Langmuir model. Moreover, the pseudo‐second‐order kinetic model better described the kinetic behavior of Cd adsorption for the investigated adsorbents. The maximum Cd removal efficiency (99%) belonged to soil No. 2 with biochar. Lastly, it was concluded that sunflower biochar, a cheap and cost‐effective adsorbent, had high efficiency in Cd adsorption in calcareous soils.

Adsorptive removal of cadmium (II) from wastewater using activated carbon synthesized from stem of Khat (Catha edulis)

IntroductionCadmium is among the most hazardous heavy metals, posing the greatest risk to human beings and the environment. Adsorption with activated carbon prepared from agricultural waste is the most effective way to remove cadmium (II) from wastewater. In this study, activated carbon prepared from the stem of Khat (Catha edulis) plant was used for the removal of cadmium (II) from wastewater. ObjectiveTo evaluate the efficiency and mechanism of the removal of cadmium (II) from wastewater using Khat (Catha edulis) stem activated carbon at different operating parameters. MethodProximate and Fourier transform infrared analyses were conducted to characterise the prepared Khat stem-activated carbon. The effects of initial cadmium concentration, adsorbent dose, pH, contact time, and agitation speed on the cadmium removal efficiency of Khat stem-activated carbon were evaluated. Furthermore, isotherm and kinetic models of adsorption were used to evaluate the mechanism of cadmium removal. ResultThe proximate analysis indicated that the activated carbon derived from Khat stems possesses a bulk density of 0.58 g/cm3 and surface area of 615 m2/g. Additionally, the prepared Khat stem activated carbon has 4 %, 14 %, and 22 % of moisture content, ash content, and volatile matter, respectively. Furthermore, the proximate analysis indicated that the Khat stem activated carbon has a porosity of 55 %. The Fourier transformed infrared spectroscopy result indicated the presence of phenolic, alcoholic, and carboxylic acid functional groups on the surface of Khat stem activated carbon. The experimental data showed a better fit with the Langmuir isotherm model (R-squared and chi-square value of 0.9727 and 1.3936, respectively) and the pseudo-second-order kinetic model (R-squared and chi-square values of 0.9032 and 0.2179, respectively). The highest adsorption efficiency of cadmium (97 %) was attained at an adsorbent dose of 0.125 g, a contact time of 30 min, an initial cadmium concentration of 20 mg/L, a pH of 5, and an agitation speed of 100 rpm at room temperature (25 °C). ConclusionThe results obtained in this research demonstrated that activated carbon from Khat stems can be employed as an economical, ecologically friendly, easily accessible and efficient activated carbon to remove Cd (II) from wastewater.

Synthesis of polyaniline tannate-modified carbon nanotubes by oxidative copolymerization as highly efficient corrosion inhibitors for mild steel in HCl solution

Corrosion is a prevalent issue in industrial production, directly impacting the production process and causing severe damages. To mitigate this problem, corrosion inhibitors are highly desired. Herein, a novel type of nano corrosion inhibitor, referred to as PTCNT, was synthesized through an oxidative copolymerization method utilizing aniline, ammonium persulfate (APS), and tannic acid (TA)-modified multiwalled carbon nanotubes (MWCNTs). The results demonstrated that the PTCNT effectively inhibited the corrosion of mild steel in 1 M HCl solution, achieving the corrosion inhibition efficiency of 90.6 % at the concentration of 75 mg/L. Characterization results implied that the PTCNT adsorbed onto the surface of the mild steel, forming a protective shielding layer. Potentiodynamic polarization measurements proved that the PTCNT functioned as the hybrid corrosion inhibitor. Furthermore, the adsorption of PTCNT on the mild steel surface was investigated using adsorption isotherm and adsorption kinetic modeling. Quantum chemical calculations were used to elucidate the adsorption mechanism of PTCNT. These findings raise new avenues for the development of highly efficient corrosion inhibitors for the mild steel in HCl solutions.

Utilization of natural and chemical activation corncob as adsorbent for continuous purification of used cooking oil using adsorption column

Abstract Corncob waste can be utilized for various purposes. The purpose of this research is to determine corncob adsorption ability and adsorption kinetics model of purified used cooking oil using natural and activated corncobs which is effective and economical method due to its low cost, simple, and regenerative. The research method used in this research is experimental. This study consisted of three stages, namely the manufacture adsorbent of natural and activated corncobs, purification, determination turbidy of used cooking oil. The natural corncob adsorbent turbidity is 13.2 NTU and the activated corncob adsorbent turbidity is 10.8 NTU. Percentage removal efficiency of natural corncob adsorbent is 97.238% and activated corncob adsorbent is 97.741%. It is shown from the pseudo-second-order graph that a chemical interaction occurs, the value of the coefficient of determination (R2) obtained is 1, using natural and activated corncob adsorbent.

Effect of the Total Saponins of Bupleurum chinense DC. Water Extracts Following Ultrafiltration Pretreatment on Macroporous Resin Adsorption.

Macroporous resin is an efficient separation technology that plays a crucial role in the separation and purification of traditional Chinese medicine (TCM). However, the application of macroporous resins in TCM pharmaceuticals is hindered by serious fouling caused by the complex materials used in TCM. This study examines the impact of ultrafiltration (UF) membrane technology on the macroporous resin adsorption behavior of TCM extracts. In this paper, Bupleurum chinense DC. (B. chinense) water extracts were included as an example to study the effect of UF pretreatment on the macroporous resin adsorption of total saponins. The study results indicated that the adsorption of total saponins constituents from the water extracts of B. chinense on the macroporous resin followed the pseudo-second-order kinetic model and the Langmuir model. The thermodynamic parameters of adsorption, including enthalpy changes and Gibbs free energies, were negative, while entropy changes were positive. These results demonstrated that the total saponin components form a monolayer adsorption layer by spontaneous thermal adsorption on the macroporous resin, and that the adsorption rate is not determined by the rate of intraparticle diffusion. Following treatment with a UF membrane with an average molecular weight cut-off of 50 kDa, the protein, starch, pectin, tannin, and other impurities in the water extracts of B. chinense were reduced, while the total saponin content was retained at 82.32%. The adsorption kinetic model of the saponin constituents on the macroporous resin remained unchanged and was consistent with both the second-order kinetic model and the Langmuir model; the adsorption rate of the second-order kinetic model increased by 1.3 times and in the Langmuir model at 25 °C, the adsorption performance improved by 1.16 times compared to the original extracts. This study revealed that UF technology as a pretreatment method can reduce the fouling of macroporous resin by TCM extracts and improve the adsorption performance of macroporous resin.

Synthesis of Silica-Based Imprinted Ionic from Rice Husk Ash for Adsorption of Ni(II)

Imprinted ionic synthesis through the sol-gel process for Ni (II) adsorption has been carried out. Sodium silicate from rice husk ash (NaSiO3(RHA)), N1-(3 Trimethoxysilylpropyl) diethylenetriamine (TMPDT) and Ni (II) are stirred, then 6 M HCl is added until a gel forms. Furthermore, 0.1 M EDTA and 0.1 M HNO3 were added to the dry gel to release Ni (II) to form-imprinted ionic material (SiO2-TMPDT-Ni-Imp). The material was characterized using FTIR, SAA, and SEM-EDX. FTIR characterization of SiO2-TMPDT-Ni-Imp indicated the appearance of-OH, -CH, -Si-O-and-NH absorption. The SAA characterization results show a surface area of 18.091 m2/g, a total pore volume of 0.033 cc/g, and an average pore radius of 16.739 Å. The optimum conditions for Ni (II) adsorption by SiO2-TMPDT-Ni-Imp are pH four and a contact time of 100 minutes. The appropriate adsorption kinetic model for the absorption of Ni (II is pseudo-second order with an adsorption capacity of 6.9 mg/g. Keywords: Silica, imprinted ionic, rice husk ash, adsorption, Ni (II)

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Sustainable Activated Carbon from Agricultural Waste: A Study on Adsorption Efficiency for Humic Acid and Methyl Orange Dyes

In this study, porous activated carbon was produced from coffee waste and used as an effective adsorbent for the removal of humic acid (HA) from seawater and methyl orange (MO) dye from aqueous solutions. Phosphoric acid H3PO4 was used as an activating agent for the chemical activation of these agricultural wastes. The characterization of the activated carbon obtained using a scanning electron microscope (SEM), Fourier-transform infrared (FTIR) spectroscopy analysis, X-ray diffraction (XRD) and the Brunauer–Emmett–Teller (BET) method revealed that the activated carbon products exhibited high porosity and the formation of various functional groups. The effects of different parameters were examined using batch adsorption experiments, such as the adsorbent masses, pH, initial pollutant concentration and contact time. The results show that the performance increased with an increased adsorbent mass (up to 0.25 g/L) and decreased initial concentration of the adsorbent tested. On the other hand, this study clearly showed that the adsorption efficiency of the MO on the raw spent coffee grounds (SCGs) waste was around 43%, while no removal was observed for the humic acid. The experiments demonstrated that the activated carbon synthesized from the used coffee grounds (the efficiency was compared with commercial activated carbon (CAC) with a difference of 13%) was a promising alternative to commercially available adsorbents for the removal of humic acid from seawater. To understand and elucidate the adsorption mechanism, various isothermal and kinetic models were studied. The adsorption capacity was analyzed by fitting experimental data to these models. The experimental data for methyl orange dyes were analyzed using Langmuir and Freundlich isothermal models. The Freundlich isotherm model provided a superior fit to the equilibrium data, as indicated by a higher correlation coefficient (R2) than that of the Langmuir model. The maximum adsorption was observed at pH 3. The Freundlich adsorption capacity was found to be 333 mg/g adsorbent. The PAC showed a high adsorption capacity for the MO and HA. The PAC showed the highest adsorption capacities for the HA and MO compared with the other adsorbents used (SCGs and CAC) and would be a good material to increase the adsorption efficiency for humic acid removal in the seawater pretreatment process. In addition, the prepared AC BET surface area was 520.40 m2/g, suggesting a high adsorption capacity. This makes the material potentially suitable for various applications that require a high surface area. These results indicate that high-quality sustainable activated carbon can be efficiently produced from coffee waste, making it suitable for a wide range of adsorbent applications targeting various pollutants.

Efficient adsorption and performance optimization of coal fly ash/desulphurized manganese residue composite microspheres on dyes

Coal fly ash (CFA) and desulphurized manganese residue (DMR), as industrial solid wastes featuring high storage capacity but low utilization rate and high environmental risk, were used to develop composite microsphere adsorbents for dye removal from industrial wastewater. The microspheres were prepared using spray drying combined with low-temperature sintering, facilitated by DMR, resulting in a uniform size distribution and quartz and mullite as the major phases. The microspheres have porous structures with abundant functional groups and those with 10 wt% DMR sintered at 800 °C have the optimal adsorption property. With 80 g/L dosage of the optimized microspheres, the removal efficiency of malachite green (MG) reaches 99.6 %. The adsorption process follows the pseudo-second-order kinetic and Langmuir isotherm adsorption models, with van der Waals force, hydrogen bond, and electrostatic attraction promoting the adsorption. After three regeneration cycles, the dye removal efficiency reaches up to 96 %, indicating broad prospects in filtration and adsorption.

Adsorption effect for removing fluoride with species of nitrogen by using La-BDC-NH2/C3N4: Experiments and mechanism

Fluoride contamination has emerged as a significant global environmental concern, with prolonged consumption of fluoride-rich groundwater being a primary contributor to fluorosis. Nitrogen sites play an important role in the process of fluoride removal, but the influence of different nitrogen species on fluoride adsorption has not been clearly clarified. In this study, a lanthanide organic framework adsorbent La-MOF-NH2 was prepared by solvothermal method, and a new adsorbent La-MOF-NH2@g-C3N4 was synthesized by adding g-C3N4 rich in various nitrogen sources. The effects of adsorbent dosage, pH, temperature and co-existing anions on the adsorption of fluorine were systematically studied. Optimal conditions were identified at a dosage of 2 g/L and a pH of 3, achieving theoretical maximum adsorption capacities of 219.4406 mg/g and 63.1401 mg/g, respectively. The results of five regeneration experiments shown that La-MOF-NH2 and La-MOF-NH2@g-C3N4 have strong recovery capacity. According to the adsorption isotherm and kinetic model, the adsorption mechanism of fluoride ions is mainly hydrogen bonding and chemisorption. In addition, through the experimental characterization and mechanism study, it was proved that amino group > pyridinic nitrogen > graphitic nitrogen. It provides a good guide for designing adsorbents containing nitrogen sites.