Nitrogen‐Doped Graphitic Carbon Nitride With Defect‐Rich Structure for Efficient Pb (II) and Cd (II) Removal From Aqueous Solutions

This study focuses on the development and evaluation of a novel composite material, designated as CF@PANi, which integrates coffee husk and polyaniline for the purpose of ammonium adsorption from aqueous solutions. The composite was synthesized under optimized conditions and characterized using various analytical techniques. The results from SEM and EDS indicated significant structural and compositional changes following the adsorption process, including an increase in porosity and a notable rise in nitrogen content from 6.35% to 17.24%, thereby confirming effective ammonium uptake. BET analysis revealed that the synthesized composite possesses a mesoporous structure with a surface area of 7.0642 m2 g-1. FTIR spectroscopy identified active functional groups, such as amine (-NH, -NH2) and hydroxyl (-OH), critical for adsorption. Batch adsorption experiments were conducted to assess the effects of various parameters, including pH, adsorbent dosage, contact time and initial ammonium concentration, on adsorption performance. The optimal conditions for ammonium adsorption were determined to be at a pH of 7, with a PANi : CF ratio of 1 : 2 and a contact time of 40 min, achieving a maximum adsorption capacity (q e) of 25.05 mg g-1, as predicted by the Langmuir isotherm model. Kinetic studies indicated that the adsorption process follows a pseudo-second-order model. The mechanistic analysis highlighted key processes involved in ammonium adsorption, including electrostatic attraction, cation exchange, surface complexation, physical adsorption, and cation-π interactions.

The removal of molybdenum (VI) from contaminated water is challenging due to its high solubility and environmental mobility. This study explores the zirconium-based metal–organic framework UiO-66 as an efficient adsorbent for Mo(VI) removal and elucidates its adsorption mechanism through systematic physicochemical and kinetic analyses. UiO-66 was synthesized via a solvothermal method, and its crystalline structure, functional groups, morphology, and porosity were confirmed by XRD, FTIR, SEM, TEM, and N2 adsorption–desorption analyses, indicating the formation of a stable and highly porous framework. Batch adsorption experiments were conducted to investigate the effects of pH, temperature, contact time, initial concentration, and competing ions. The adsorption process exhibited strong pH dependence, with optimal performance at pH 3. Under these conditions, UiO-66 achieved a maximum adsorption capacity of 275.9 ± 0.9 mg g−1 at 45 °C, outperforming many conventional adsorbents. Kinetic data followed the pseudo-second-order model (R 2 = 0.998), suggesting chemisorption as the rate-limiting step, while equilibrium data were best described by the Langmuir isotherm, indicating monolayer adsorption on homogeneous sites. Selectivity studies confirmed preferential Mo(VI) uptake in the presence of competing ions. Thermodynamic analysis revealed that the adsorption is spontaneous (ΔG < 0) and endothermic (ΔH > 0). Additionally, UiO-66 demonstrated excellent reusability over five adsorption–desorption cycles, maintaining high efficiency and structural stability. The adsorption mechanism is mainly attributed to electrostatic attraction and coordination interactions between molybdate species and Zr–O clusters. These findings highlight UiO-66 as a promising material for efficient water purification applications.

Phosphorylated chitosan/CoFe2O4 composite for the efficient removal of Pb(II) and Cd(II) from aqueous solution: Adsorption performance and mechanism studies

Highly efficient kaolin/g-C3N4/WO3 ternary nanocomposite for the effective removal of Arsenic ions from aqueous media

One-pot pyrolysis of metal-embedded biochar derived from invasive plant for efficient Cr(VI) removal

The removal of unsymmetrical dimethylhydrazine (UDMH) has long been a concern because of its harmful effect on the environment and humans. This study aimed to prepare a novel graphene oxide/O-carboxymethyl chitosan (GO/CMC) composite adsorbent using the solution-blending method for the removal of UDMH from wastewater. The prepared GO/CMC was systematically characterized by Fourier-transform infrared, Raman, scanning electronic microscopy, transmission electron microscopy, thermogravimetric, and zeta potential analyses. The effects of initial pH, temperature, adsorbent dosage, initial concentration, contact time, and recyclability on the UDMH adsorption behaviour of GO/CMC were studied. The adsorption kinetics was consistent with the pseudo-second-order kinetics model, and the adsorption process was mainly controlled by chemisorption. Adsorption isotherms indicated that the adsorption of UDMH by GO/CMC followed the Langmuir adsorption isotherm. The adsorption mechanisms were mainly electrostatic attraction, hydrogen bonding, and surface complexation. Furthermore, GO/CMC composites can be used as a renewable and eco-friendly adsorbent for the removal of UDMH wastewater. The designed GO/CMC composites exhibited a relatively satisfactory recyclability and removal efficiency after five adsorption–desorption cycles.

Heavy metals are the most dangerous inorganic pollutants Due to their bioaccumulation and their nonbiodegradability, for this, several studies have focused on the recovery of these metals from water using different techniques. In this context, our study consists of evaluating an efficient and eco-friendly pathway of competitive recovery of heavy metals (Cd, Cr and As) from aqueous solutions by adsorption using raw rock. This adsorbent was characterized before and after the adsorption process by several techniques. The multi-metals adsorption process in the batch mode was undertaken to evaluate the effect of adsorbent mass, contact time, pH, Temperature, and initial heavy metals concentration. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. According to the modeling of the experimental results, the adsorption kinetics of heavy metals were adapted to the pseudo-second-order model. The adsorption isotherms were evaluated by the Langmuir and Freundlich isotherm models. The experimental isotherm data of heavy metals were better fitted with the Langmuir model rather than Freundlich isotherm models. The maximum experimental adsorption capacities (Qmax) predicted by the Langmuir model are 15.23 mg/g for Cd (II), 17.54 mg/g for Cr (VI) and 16.36 mg/g for As (III). The values of thermodynamic parameters revealed that the heavy metals adsorption was exothermic, favorable, and spontaneous in nature. The desorption process of heavy metals showed that this raw rock had excellent recycling capacity. Based on the results, these untreated clays can be used as inexpensive and environmentally friendly adsorbents to treat water contaminated by heavy metals.

Cadmium is one of the most toxic cations and harmful to human health and the environment. In this work, a magnetic hydroxyapatite (HAP) modified maghemite (γ-Fe2O3) nanocomposite was successfully prepared as adsorbent for the removal of aqueous Cd(II) with outstanding adsorption performance. The X-ray diffraction analysis (XRD), field emission transmission electron microscope (TEM), vibrating sample magnetometer (VSM) analysis, and Fourier-transform infrared spectroscopy (FTIR) were used for characterization of the adsorbent. The characterization results showed that the obtained nanocomposite was composed of γ-Fe2O3 and HAP and exhibited a superparamagnetic property. Considering the good separation characteristic after use, the HAP modified γ-Fe2O3 nanocomposite was used as an adsorbent for the removal of Cd(II) from aqueous solution. The effects of initial pH, adsorbent dosage, contact time, temperature, coexisting ions, and the presence of humic acid on Cd(II) adsorption were investigated. Results showed that the adsorption of Cd(II) was strongly dependent on pH, and the adsorption data could be well fitted by the Langmuir model, and the adsorption kinetics followed the pseudo-second-order model. Compared with pure HAP or γ-Fe2O3, the prepared nanocomposite had higher adsorption ability toward Cd(II). The maximum adsorbed capacity was found to be 277.78 mg/g, which was much higher than previously reported HAP or γ-Fe2O3 based adsorbents. Furthermore, the main mechanisms for Cd(II) removal was suggested to be electrostatic interaction, ion-exchange, and surface complexation. Thus, the HAP modified γ-Fe2O3 nanocomposite showed great potential as a magnetically separable adsorbent for the removal of Cd(II) from polluted water.

This study describes the adsorption of Cu (II), Co (II) and Ni (II) ions from wastewater on Vigna radiata husk biomass. The ability of adsorbent to capture the metal ions has been found to be in the order of Ni (II)&gt;Co (II) and Cu (II) depending upon the size and nature of metal ions to be adsorbed. It has been observed that percentage removal of Cu (II), Co (II) and Ni (II) ions increases with increase of adsorbent dosage, contact time and pH of the medium but up to a certain extent. Maximum adsorption capacity (qmax) for Cu (II), Co (II) and Ni (II) ions has been found to be 11.05, 15.04 and 19.88 mg/g, respectively, under optimum conditions of adsorbent dosage, contact time and pH of the medium. Langmuir model best fits the adsorption process with R2 value approaches to unity for all metal ions as compared to other models because adsorption sites are seemed to be equivalent and only monolayer adsorption may occur as a result of binding of metal ion with a functional moiety of adsorbent. Pseudo second order kinetic model best interprets the adsorption process of Cu (II), Co (II) and Ni (II) ions. Thermodynamic parameters such as negative value of Gibbs energy (∆G°) gives information about feasibility and spontaneity of the process. Adsorption process was found to be endothermic for Cu (II) ions while exothermic for Co (II) and Ni (II) ions as signified by the value of enthalpy change (∆H°). Husk biomass was recycled three times for removal of Ni (II) from aqueous medium to investigate its recoverability and reusability. Moreover V. radiata husk biomass has a potential to extract Cu (II) and Ni (II) from electroplating wastewater to overcome the industrial waste water pollution.

This work aims to enhance the adsorption performance of Laponite @diatomite for organic pollutants by modifying it with cetyltrimethylammonium bromide (CTAB). The microstructure and morphology of the CTAB-modified Laponite @diatomite material were characterized using SEM, XRD, FTIR, BET, and TG. Furthermore, the influences of key parameters, containing pH, adsorbent dosage, reaction time, and reaction temperature, on the adsorption process were investigated. The kinetics, thermodynamics, and isotherm models of the adsorption process were analyzed. Finally, potential adsorption mechanisms were given based on the characterization. The research findings indicate that CTAB-La@D exhibits good adsorption performance toward Congo red (CR) over a broad pH range. The maximum adsorption capacity of CR was 451.1 mg/g under the optimum conditions (dosage = 10 mg, contact time = 240 min, initial CR concentration = 100 mg/L, temperature = 25 °C, and pH = 7). The adsorption process conformed to the pseudo-second-order kinetic model, and the adsorption isotherms indicated that the adsorption process of CR was more in line with the Langmuir model, and it was physical adsorption. Thermodynamic analysis illustrates that the adsorption process is exothermic and spontaneous. Additionally, the mechanisms of electrostatic adsorption and hydrophobic effect adsorption of CR were investigated through XPS and FTIR analysis. This work provides an effective pathway for designing high-performance adsorbents for the removal of organic dye, and the synthesized materials hold great capability for practical utilization in the treatment of wastewater.

A novel composite of SiO2 decorated with nano ferrous oxalate (SDNF) for efficient and highly selective removal of Pb2+ from aqueous solutions

The discharge of synthetic dyes in industrial wastewaters poses a serious environmental threat as they are difficult to degrade naturally and are harmful to aquatic organisms. This study aimed to evaluate the feasibility of using clean untreated rice husk (CRH) as a sustainable and low-cost adsorbent for the removal of methylene blue (MB) from synthetic wastewater. This approach effectively avoids the energy-intensive grinding process by directly using whole unprocessed rice husk, highlighting its potential as a sustainable and cost-effective alternative to activated carbon. A series of batch adsorption experiments were conducted to evaluate the effects of key operating parameters such as initial dye concentration, contact time, pH, ionic strength, and temperature on the adsorption performance. Adsorption kinetics, isotherm models, and thermodynamic analysis were applied to elucidate the adsorption mechanism and behavior. The results showed that the maximum adsorption capacity of CRH for MB was 5.72 mg/g. The adsorption capacity was stable and efficient between pH 4 and 10, and reached the highest value at pH 12. The presence of sodium ions (Na+) and calcium ions (Ca2+) inhibited the adsorption efficiency, with calcium ions having a more significant effect. Kinetic analysis confirmed that the adsorption process mainly followed a pseudo-second-order model, suggesting the involvement of a chemisorption mechanism; notably, in the presence of ions, the Elovich model provided better predictions of the data. Thermodynamic evaluation showed that the adsorption was endothermic (ΔH° &gt; 0) and spontaneous (ΔG° &lt; 0), accompanied by an increase in the disorder of the solid–liquid interface (ΔS° &gt; 0). The calculated activation energy (Ea) was 17.42 kJ/mol, further supporting the involvement of chemisorption. The equilibrium adsorption data were well matched to the Langmuir model at high concentrations (monolayer adsorption), while they were accurately described by the Freundlich model at lower concentrations (surface heterogeneity). The dimensionless separation factor (RL) confirmed that the adsorption process was favorable at all initial MB concentrations. The results of this study provide insights into the application of agricultural waste in environmental remediation and highlight the potential of untreated whole rice husk as a sustainable and economically viable alternative to activated carbon, which can help promote resource recovery and pollution control.

The adsorption of chromate on octacalcium phosphate (OCP) was investigated as a function of contact time, surface coverage, and solution pH [...]

Highly efficient and rapid removal of a toxic dye: Adsorption kinetics, isotherm, and mechanism studies on functionalized multiwalled carbon nanotubes

Introduction – Quite often large amounts of colored wastewater are discharged into natural streams with undesirable consequences to the environment and to human health, being generated by industries that use dyes to impart a desired color to their products (food, paper, rubber, textile, plastics and others) [1]. The dye-contained effluents are supposed to be a significant concern due to the adverse effects of dye in various parts of the life cycle. The toxicological and aesthetical problems associated with release of dyes into the environment are the main reasons of these worries. Methylene blue (MB) is one of the widespread materials in dye which is used for cotton and silk painting. The most harmful effects of MB is eye burn and also create breathing problems, nausea, vomiting, profuse sweating, mental confusion and methemoglobinemia. Many treatment methods have been used to remove the dyes from industrial wastewater, which can be divided into physical, chemical, and biological methods. Among the various methods, adsorption is an effective separation process for a wide variety of applications [2]. It is now recognized as an effective and economical method for the removal of both organic and inorganic pollutants from wastewaters. Palm Tree Fiber (PTF), a residue from date farms and industry was studied as a biosorbent for the removal of Methylene blue dye (MB) from contaminated water. Experimental Adsorbent preparation and Characterization : the Palm Tree Fiber was washed, dried, grounded then sieved to different particle size and stored into plastic bag. PTF was characterized by Field Emission Scanning Microscopy/Energy Dispersive X-ray (FESEM- JEOL JSM 6360LA, Japan). The FESEM analysis was carried out at room temperature with accelerating voltage of 20 kV. Batch experiment: Study effect of different environmental factor such as, adsorbent mass, contact time, pH and temperature. All determinations were performed in a total of three replicates per experiment and the average values were reported using Ultraviolet (UV-C) with two 15-watt lamps (Philips Model) was used as a source of ultraviolet radiation at λmax = 664 nm. kinetic and isotherm models were utilized to describe the adsorption process mechanisms [3]. Environmental application and recycling. Results and Discussion - Palm Tree Fiber (PTF) residue of date farms and industry was successfully used as biosorbent for Methylene blue (MB) dye from contaminated water. The chemical composition and surface morphology of the biosorbent was critically studies figure (1). In batch separation mode, the effect of various analytical parameters (adsorbent dose, ion strength, contact time, pH, and temperature) on MB uptake by the used bio sorbent was studied. The kinetic data were also subjected to pseudo-first order and pseudo- second order mathematical models. The pseudo-second order was more predominant for MB uptake. The adsorption equilibrium data of MB retention were subjected to Langmuir to assign the most probable retention mechanism. Langmuir isotherm model indicated an adsorption in monolayers [4]. The application study showed that 99% of MB was removed from the environmental water samples, and a good removal percentage on the 2-time recycling was achieved. Conclusions - The maximum percentage removal of MB was about 99 %, at the dosage of 20 mg. Adsorption isotherms, and kinetic models were carried out for the calculation of adsorption parameters. The data a demonstrated that the Langmuir isotherm provides a better fit due to higher R2 values. The adsorption process followed a pseudo second order kinetic model indicates that the rate controlling step may be electrostatic attraction. The regenerated biomass exhibited increased dye adsorption up to two subsequent cycles. The results presented in this study indicate that PTF presents great potential as an inexpensive and easily available alternative adsorbent for the removal of cationic dyes in wastewater treatments. For a future research, modification of PTF surface to increase the efficiency of adsorption capacity. Keywords: Adsorption kinetics; Agri-food waste; Biosorption; Methylene Blue dye; Water treatment.