Adsorption behaviour of 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite for cadmium(II) from aqueous solutions

Nanocellulose-Based Adsorbents for Heavy Metal Ion

Heavy metal ions in industrial sewage constitute a serious threat to human health. Nanocellulose-based adsorbents are emerging as an environmentally friendly material platform for heavy metal ion removal based on their unique properties, which include high specific surface area, excellent mechanical properties, and biocompatibility. In this review, we cover the most recent works on nanocellulose-based adsorbents for heavy metal ion removal and present an in-depth discussion of the modification technologies for nanocellulose in the process of assembling high-performance heavy ion adsorbents. By introducing functional groups, such as amino, carboxyl, aldehyde, and thiol, the assembled nanocellulose-based adsorbents both remove single heavy metal ions and can selectively adsorb multiple heavy ions in water. Finally, the remaining challenges of nanocellulose-based adsorbents are pointed out. We anticipate that this review will provide indispensable guidance on the application of nanocellulose-based adsorbents for the removal of heavy metal ions.

Design of a Fixed-Bed Column with Vegetal Biomass and Its Recycling for Cr (VI) Treatment

The aim of this work is to design a fixed-bed column with vegetal biomass of Eichhornia crassipes and the process of recycling it for treatment via the adsorption of water loaded with chromium (VI). In the first stage, the relationship between the fixed-bed density and the microparticle density is calculated, giving a model for the design of the fixed bed. Using this model, two systems for the treatment of Cr (VI)-contaminated water were designed and built. The vegetable biomass at three particle diameters of 0.212 mm, 0.30 mm and 0.45 mm was evaluated in the removal of Cr (VI) from water using the designed fixed-bed systems, giving the best removal of Cr (VI) with the lowest size particles and allowing the validation of the proposed model with the Thomas model. The incorporation of iron into the biomass allowed for the treatment of near 2.0 L of polluted solution, removing around 90% of Cr (VI), while it was only possible to treat nearly 1.5 L when using raw biomass, removing around 80% of Cr (VI). The recycling of the biomass was achieved via the elution of Cr (VI) with EDTA, permitting the reuse of the material for more than five treatment cycles.

Preparation of novel porous Al2O3-SiO2nanocomposites via solution-freeze-drying-calcination method for the efficient removal of uranium in solution

In this work, the efficient extraction of uranium in solution using Al₂O₃-SiO₂-T was reported. Kinetics and isotherm models indicated that the removal process of uranium on Al₂O₃-SiO₂-T accorded with pseudo-second-order kinetic model and Langmuir isotherm model, which showed that the adsorption process was a uniform mono-layer chemical behavior. The maximum adsorption capacity of Al₂O₃-SiO₂-T reached 738.7 mg g^-1, which was higher than AlNaO₆Si₂(349.8 mg g^-1) and Al₂O₃-SiO₂-NT (453.1 mg g^-1), indicating that the addition of template could effectively improve the adsorption performance of Al₂O₃-SiO₂to uranium. Even after five cycles of adsorption-desorption, the removal percentage of uranium on Al₂O₃-SiO₂-T remained 96%. Besides, the extraction efficiency of uranium on Al₂O₃-SiO₂-T was 72.5% in simulated seawater, which suggested that the Al₂O₃-SiO₂-T was expected to be used for uranium extraction from seawater. Further, the interaction mechanism between Al₂O₃-SiO₂-T and uranium species was studied. The results showed that the electrostatic interaction and complexation played key roles in the adsorption process of Al₂O₃-SiO₂-T to uranium.

Design and development of a biotreatment of E. crassipes for the decontamination of water with Chromium (VI)

The use of cellulose materials for the adsorption of heavy metals has increased in favorable results to comply with the removal of these contaminants from water, such as the case of Chromium (VI), being one of the most dangerous heavy metals for the environment and human health. The objective of this research is to design and develop a biotreatment with dry and crushed biomass of E. crassipes for the continuous treatment of Chromium (VI), determining through mathematical modeling the Fick diffusion constant (Kf), based on this constant Fick will establish the performance of the biotreatment and the intraparticle diffusion constant (Ks). The diffusion speed (Kf) of the biomass of E. crassipes chemisorbing Cr (VI) of 0.30 cm/min, also it got the constant of the adsorption capacities (Ks) was 0.0198 s. With (Kf) it can design the treatment systems according to caudal or load greatly contaminated, calibrating the parameters how caudal, volume, or area of contact of the system of treatment. Also with (Ks) will be possible the design and modeling of a treatment system to improve the capacity of adsorptions calibrating the density of the particle and the density of the contact bed of the treatment system. Based on Fick's second law, an equation was designed to determine the reliability and performance of water treatment systems through the E. crassipes plant.

Design and development of a biotreatment of E. crassipes for the decontamination of water with Chromium (VI)

The use of cellulose materials for the adsorption of heavy metals has increased in favorable results to comply with the removal of these contaminants from water, such as the case of Chromium (VI), being one of the most dangerous heavy metals for the environment and human health. The objective of this research is to design and develop a biotreatment with dry and crushed biomass of E. crassipes for the continuous treatment of Chromium (VI), determining through mathematical modeling the Fick diffusion constant (Kf), based on this constant Fick will establish the performance of the biotreatment and the intraparticle diffusion constant (Ks). The diffusion speed (Kf) of the biomass of E. crassipes chemisorbing Cr (VI) of 0.30 cm/min, also it got the constant of the adsorption capacities (Ks) was 0.0198 s. With (Kf) it can design the treatment systems according to caudal or load greatly contaminated, calibrating the parameters how caudal, volume, or area of contact of the system of treatment. Also with (Ks) will be possible the design and modeling of a treatment system to improve the capacity of adsorptions calibrating the density of the particle and the density of the contact bed of the treatment system. Based on Fick's second law, an equation was designed to determine the reliability and performance of water treatment systems through the E. crassipes plant.

Estimation of equilibrium times and maximum capacity of adsorption of heavy metals by E. crassipes (review)

Cellulose emerges as an alternative for the treatment of water contaminated with heavy metals due to its abundant biomass and its proven potential in the adsorption of pollutants. The aquatic plant Eichhornia crassipes is an option as raw material in the contribution of cellulose due to its enormous presence in contaminated wetlands, rivers, and lakes. The efficiency in the removal of heavy metals is due to the cation exchange between the hydroxyl groups and carboxyl groups present in the biomass of E. crassipes with heavy metals. Through different chemical and physical transformations of the biomass of E. crassipesThe objective of this review article is to provide a discussion on the different mechanisms of adsorption of the biomass of E. crassipes to retain heavy metals and dyes. In addition to estimating equilibrium, times through kinetic models of adsorption and maximum capacities of this biomass through equilibrium models with isotherms, in order to design one biofilter for treatment systems on a larger scale represented the effluents of a real industry.

Estimation of equilibrium times and maximum capacity of adsorption of heavy metals by E. crassipes (review)

Cellulose emerges as an alternative for the treatment of water contaminated with heavy metals due to its abundant biomass and its proven potential in the adsorption of pollutants. The aquatic plant Eichhornia crassipes is an option as raw material in the contribution of cellulose due to its enormous presence in contaminated wetlands, rivers, and lakes. The efficiency in the removal of heavy metals is due to the cation exchange between the hydroxyl groups and carboxyl groups present in the biomass of E. crassipes with heavy metals. Through different chemical and physical transformations of the biomass of E. crassipesThe objective of this review article is to provide a discussion on the different mechanisms of adsorption of the biomass of E. crassipes to retain heavy metals and dyes. In addition to estimating equilibrium, times through kinetic models of adsorption and maximum capacities of this biomass through equilibrium models with isotherms, in order to design one biofilter for treatment systems on a larger scale represented the effluents of a real industry.

Synthesis and characterization of amidoxime modified chitosan/bentonite composite for the adsorptive removal and recovery of uranium from seawater

A novel amidoxime functionalized adsorbent, poly(amidoxime)-grafted-chitosan/bentonite composite [P(AO)-g-CTS/BT] was prepared by in situ intercalative polymerization of acrylonitrile (AN) and 3-hexenedinitrile (3-HDN) onto chitosan/bentonite composite using ethylene glycol dimethacrylate (EGDMA) as cross linking agent and potassium peroxy disulphate (K₂S₂O₈) as free radical initiator. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), BET surface area analyser and X-ray photoelectron spectroscopy (XPS). Nitrile groups from two monomers converted to amidoxime groups and therefore, increases the adsorption efficiency of uranium(VI) [U(VI)] from seawater. The optimum pH for U(VI) adsorption was found to be 8.0. The adsorbent dosage of 2.0 g/L was sufficient for the complete removal of U(VI) from seawater. The kinetic data fitted well with pseudo-second-order kinetic model which assumes the presence of chemisorption. The equilibrium attained within 60 min and well agreement of equilibrium data with Langmuir adsorption model confirms monolayer coverage of U(VI) onto P(AO)-g-CTS/BT. The maximum adsorption capacity was found to be 49.09 mg/g. Spent adsorbent was effectively regenerated using 0.1 N HCl. Six cycles of adsorption-desorption experiments were conducted to study the practical applicability and repeated use of the adsorbent. The feasibility of the adsorbent was also tested using natural seawater. The results show that P(AO)-g-CTS/BT is a promising adsorbent for the removal of U(VI) from seawater.

Efficient removal of cadmium from soil-washing effluents by garlic peel biosorbent

Paddy field soil contaminated by cadmium may produce cadmium-contained corns causing Itai-itai disease, and in situ washing of soil with the organic acid is a good technical choice due to its convenience and cost-effectiveness. While the bottleneck of this technique is how to recycle the huge volume of washing effluent in an efficient and economical way. Biosorption of cadmium on the garlic peel was attempted in present study and it was found quite satisfactorily effective to remove all cadmium from the real soil leaching effluent after three-time sequential adsorption. The systematical investigation on the effect of various parameters on the adsorption of cadmium on garlic peel in the existence of tartaric ligand was performed and it was found that tartrate could change Cd²⁺ into Cd(tar)⁰ species whose electrical charge state would restrain its approach to the adsorbent particles. The porous microstructure in the transversal surface of garlic peel and the abundant groups of -COOH are the main factors affecting the adsorption capability. A demonstrative flowsheet of soil remediation by chemical washing coupled with biosorption was proposed correspondingly, in which the cadmium could be recovered from the soil washing effluent, and the recovered effluent was reused for next soil washing, and recovered garlic peel was reused for cadmium adsorption from the effluents again, showing a great prospect in the remediation of paddy field soil contaminated by cadmium. Garlic peel was used to remove the cadmium from the soil washing effluent.

Removal of cadmium from a citrate-bearing solution by floatable microsized garlic peel

Garlic peel was chosen as an effective adsorbent for a cadmium-contaminated soil remediation process.

Synthesis and characterization of polyacrylic acid- grafted-carboxylic graphene/titanium nanotube composite for the effective removal of enrofloxacin from aqueous solutions: Adsorption and photocatalytic degradation studies

Polyacrylic acid-grafted-carboxylic graphene/titanium nanotube (PAA-g-CGR/TNT) composite was synthesized. It was effectively used as adsorbent as well as photocatalyst. The composite was characterized by FTIR, XRD, SEM, TEM, Surface Area Analyzer, XPS and DRS. The photocatalytic activity of PAA-g-CGR/TNT composite was evaluated on the basis of the degradation of pollutants by using sunlight. The band gap of the prepared photocatalyst was found to be 2.6eV. The removal of the antibiotic enrofloxacin (ENR) was achieved by two step mechanism based on adsorption and photodegradation. The maximum adsorption was observed at pH 5.0. The best fitted kinetic model was found to be pseudo-second-order. The maximum adsorption was observed at 30°C. The maximum adsorption capacity was found to be 13.40mg/g. The kinetics of photodegradation of ENR onto PAA-g-CGR/TNT composite follow first-order kinetics and optimum pH was found to be 5.0. The regeneration and reuse of the adsorbent-cum-photocatalyst were also examined upto five cycles.