Effective of mercury (II) removal from contaminated water using an innovative nanofiber membrane: Kinetics, isotherms, and optimization studies

The study aimed to evaluate enhancements in both stability and efficiency concerning the removal of Hg(II) ions. This research specifically concentrated on creating an innovative electrospun nanofibrous membrane (CPP) that is made up of chitosan (CS), polyethylenimine (PEI), and polycaprolactone (PCL). The membrane's primary purpose is to enhance the elimination of Hg(II) from aqueous solutions. By carefully adjusting the electrospinning process variables, we improved its efficiency. Characterization techniques like FTIR, XRD, XPS, SEM, and EDX confirm the successful creation of a highly crosslinked CPP nanofiber membrane. This detailed examination reveals the textural attributes of the material, concurrently underlining its relevance in various domains. The investigation additionally delves into the impact of several aspects on the adsorption mechanism, comprising dosage, pH levels, temperature, and initial Hg(II) concentration. The research incorporates an analysis of adsorption characteristics by integrating kinetic evaluations with equilibrium studies. The findings indicate that the adsorption mechanism aligns with the values of pseudo-second-order kinetics and is appropriately represented by the Langmuir isotherm model. Furthermore, the data suggest a hybrid nature of the adsorption procedure, exhibiting both spontaneous and endothermic characteristics, as showed by the increased metal adsorption at elevated temperatures. The analysis reveals that optimal conditions for the elimination of Hg(II) ions in water purification involve a pH of 6 and the use of 0.02 g of CPP per 25 mL of solution, corresponding to a projected adsorption capability of 393.043 mg/g precisely for the Hg(II) ions solution. To enhance the efficacy of the adsorbent in the elimination of Hg(II) ions from water, several key parameters require careful examination. Notable advancements in adsorption performance have been achieved through the application of response surface methodologies and structured experimentation utilizing the Box-Behnken design, facilitated by the Design-Expert software. A thorough evaluation of the reusability of the adsorbent, conducted during five consecutive cycles of adsorption and desorption, shows a remarkable stability in its ability to efficiently remove Hg(II) ions.

Synthesis of pomegranate peel-activated carbon encapsulated onto carboxymethylcellulose and polyethylenimine for cadmium (II) adsorption: Optimization, kinetics and isotherm modeling

This research explores pomegranate peel as a precursor for activated carbon to eliminate cadmium (II) ions from aqueous solutions. The produced activated carbon was encapsulated with carboxymethylcellulose and polyethylenimine, then crosslinked with epichlorohydrin to form activated carbon carboxymethylcellulose and polyethyleneimine (ACCP) hydrogel beads. Numerous analytical methods were working to characterize the adsorbent, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and nitrogen adsorption/desorption isotherms. The BET analysis revealed a surface area of 110.02 m2/g, indicating a highly porous material with numerous active adsorption sites. A pore volume of 0.13 cc/g shows significant capacity for retaining adsorbed ions. The average pore radius of 1.88 nm classifies as mesopores, typically found near the transition between micropores and mesopores. Examine the influence of various factors, including pH, concentration of Cd(II), amount of adsorbent, duration of contact, and temperature, on the adsorption process. The adsorption isotherm monitored the Langmuir equation, suggesting a specific adsorption procedure. Kinetics were defined by the pseudo-second-order model, linking the adsorption rate to the square of unoccupied sites. Thermodynamic parameters yielded ΔHo of 97.94 kJ/mol and ΔSo of 334.8 J/mol.K, indicating an endothermic and spontaneous adsorption process. Various mechanisms for Cd(II) interaction with ACCP may include ion exchange, electrostatic forces, or complexation. Data indicate that optimal parameters for efficient Cd(II) removal in water are a pH of 6, 0.02 g of ACCP per 25 mL solution, and an adsorption capacity of 301.6 mg/g. To enhance the adsorbent's efficacy, various influential parameters must be thoroughly examined. A Box-Behnken design (BBD) and response surface methodology (RSM) are used to help identify the ideal conditions for Cd(II) adsorption. An investigation of the adsorbent's reusability over five cycles shows a substantial reliability for removal applications.

Cellulose nanocrystals from agriculture and forestry biomass: synthesis methods, characterization and industrial applications

Agricultural and forestry biomass wastes, often discarded or burned without adequate management, lead to significant environmental harm. However, cellulose nanocrystals (CNCs), derived from such biomass, have emerged as highly promising materials due to their unique properties, including high tensile strength, large surface area, biocompatibility, and renewability. This review provides a detailed analysis of the lignocellulosic composition, as well as the elemental and proximate analysis of different biomass sources. These assessments help determine the yield and characteristics of CNCs. Detailed discussion of CNC synthesis methods -ranging from biomass pretreatment to hydrolysis techniques such as acid, mineral, solid acid, ionic liquid, and enzymatic methods-are provided. The key physical, chemical, and thermal properties of CNCs are also highlighted, particularly in relation to their industrial applications. Recommendations for future research emphasize the need to optimize CNC synthesis processes, identify suitable biomass feedstocks, and explore new industrial applications.

Cellulose Nanocrystals (CNCs) and Cellulose Nanofibers (CNFs) as Adsorbents of Heavy Metal Ions

The isolation of nanocellulose has been extensively investigated due to the growing demand for sustainable green materials. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), which have the same chemical composition but have different morphology, particle size, crystallinity, and other properties depending on the precursor and the synthesis method used. In comparison, CNC particles have a short rod-like shape and have smaller particle dimensions when compared to CNF particles in the form of fibers. CNC synthesis was carried out chemically (hydrolysis method), and CNF synthesis was carried out mechanically (homogenization, ball milling, and grinding), and both can be modified because they have a large surface area and are rich in hydroxyl groups. Modifications were made to increase the adsorption ability of heavy metal ions. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG), and dynamic light scattering (DLS) can reveal the characteristics and morphology of CNCs and CNFs. The success and effectiveness of the heavy metal adsorption process are influenced by a few factors. These factors include adsorbent chemical structure changes, adsorbent surface area, the availability of active sites on the adsorbent’s surface, adsorption constants, heavy metal ionic size differences, pH, temperature, adsorbent dosage, and contact time during the adsorption process. In this review, we will discuss the characteristics of CNCs and CNFs synthesized from various precursors and methods, the modification methods, and the application of CNCs and CNFs as heavy metal ion adsorbents, which includes suitable isotherm and kinetics models and the effect of pH on the selectivity of various types of heavy metal ions.

Recent advancements in engineered biopolymeric-nanohybrids: A greener approach for adsorptive-remediation of noxious metals from aqueous matrices

Industrial wastewater is causing serious health problems due to presence of large concentrations of toxic metals. Removal of these metals is still a big challenge using pristine natural biopolymers due to their low surface area, water solubility, and poor recovery. Developing biopolymeric composites with other materials has attained attention because they possess a high surface area and structural porosity, high reactivity, and less water solubility. In simple words, biopolymeric nanohybrids have great adsorption capacity for heavy metals. Biopolymeric materials are abundant, low cost, biodegradable, and possess different functional moieties (carboxyl, amine, hydroxyl, and carbonyl) which play a vital role to adsorb metal ions through various inter-linkages (i.e., electrostatic, hydrogen bonding, ion exchange, chelation, etc.). Biopolymeric nanohybrids have been proven a potent tool in environmental remediation such as the abatement of heavy metal ions from polluted water. Herein, we have reported the adsorption potential of various biopolymers (cellulose, chitosan, pectin, gelatin, and silk proteins) for the removal of heavy metals. This review discusses the suitability of biopolymeric nanohybrids as an adsorbent for heavy metals, their synthesis, modification, adsorption potential, and adsorption mechanism along with best fitted thermodynamic and kinetic models. The influence of pH, contact time, and adsorbent dose on adsorption potential has also been discussed in detail. Lastly, the challenges, research gaps and recommendations have been presented. This review concludes that biopolymers in combination with other materials such as metal-based nanoparticles, clay, and carbon-based materials are excellent materials to remove metallic ions from wastewater. Significant adsorption of heavy metals was obtained at a moderate pH (5-6). Contact time and adsorbent dose also affect the adsorption of heavy metals in certain ways. The Pseudo-first order model fits the data for the initial period of the first step of the reaction. Kinetic studies of different adsorption processes of various biopolymeric nanohybrids described that for majority of bionanohybrids, Pseudo-second order fitted the experimental data very well. Functionalized biopolymeric nanohybrids being biodegradable, environment friendly, cost-effective materials have great potential to adsorb heavy metal ions. These may be the future materials for environmental remediation.