Comparison between removal of Ethidium bromide and eosin by synthesized manganese (II) doped zinc (II) sulphide nanoparticles: kinetic, isotherms and thermodynamic studies

Removal of heavy metals from the aqueous solution by nanomaterials: a review with analysing and categorizing the studies

With the development of nanotechnology and its application in various sciences, scientists have investigated the use of nanoparticles as adsorbents to remove heavy metals from aqueous solutions all over the world. So far, the results of many of these studies have been published in reputable journals. Obviously, reviewing these articles and summarizing the results of these studies from different aspects will provide new perspectives for the development of this technology for heavy metals removal from water. So the current study was performed to review the results of the published studies between 1/January/1980 to 1/January/2022. The focus of the study is on the analysis of these studies and their classification. In addition, a more detailed investigation was carried out. Among the 5155 articles, 576 articles were included based on Cochrane protocols. Results show that most of the studies (90.8%) were conducted on a laboratory scale and used synthetic solutions. Most studies were performed for Pb, Cd and Cu, removal respectively. Compared to other countries, authors with affiliation from China and Iran have published more articles. The ranking of the use of various nanomaterials were: nanocomposites > metal oxide nanomaterials > metal-based nanomaterials > carbon-based nanomaterials > dendrimers, with the wide range of sizes from less than 10 nm to several hundreds of nanometers. The required amount of carbon-based nanoparticles to remove many heavy metals were lower than other nanoparticles. In most studies, pH ≤ 7 has been reported as optimal. Most studies have been followed pseudo second-order and pseudo first-order reactions and have been more agreement with Langmuir and Freundlich adsorption isotherms respectively. The results of studies show that the synthesis and optimization of new nanomaterials can be considered as a new and competitive technology. However, more studies are needed to investigate the removal of heavy metals in real samples and to overcome some challenges in the full-scale application.

Gum katira-silver nanoparticle-based bionanocomposite for the removal of methyl red dye

The present study aimed to synthesize gum katira-silver nanoparticle-based bionanocomposite. Different characterization techniques were used to analyze the synthesized bionanocomposite, such as Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), and transmission electronic microscopy (TEM). AgNPs were formed and were 6-20 nm in size. Thermo-gravimetric analysis showed that synthesized nanocomposites are more thermally stable than gum katira. All the reaction conditions, such as time, temperature, pH, solvent, amount of nanoparticles, the concentration of the initiator, crosslinker, and monomer were optimized with respect to swelling. The results showed that the highest percentage swelling (Ps) of Gk-cl-poly(AA) was 796%, and 867% of AgNPs were imbibed by Gk-cl-poly(acrylic acid)-AgNPs. Synthesized bionanocomposite was used as an adsorbent material for the adsorption of methyl red (MR) dye. The effects of different reaction conditions were also optimized to attain maximum adsorption of MR dye. The maximum dye adsorption through Gk-cl-poly(AA)-AgNPs bionanocomposite was 95.7%. Diverse kinetic and isotherm models were used to study the adsorption data. The R ² value was established as 0.987 and k₂ was .02671. The greater R ² value of second-order kinetics over first-order kinetics suggested that MR adsorption by nanocomposite is best explained by pseudo-second-order kinetics, indicating that dye adsorption occurred through chemisorption. The R ² value was determined to be .9954. The correlation coefficient values of Gk-cl-poly(AA)-AgNPs were best fitted by the Freundlich adsorption isotherm. Overall, synthesized bionanocomposite is a proficient material for removing of MR dye from wastewater.

Adsorption and removal of ethidium bromide from aqueous solution using optimized biogenic catalytically active antibacterial palladium nanoparticles

Due to being low cost and eco-friendly, biological nanomaterial synthesis and development have made broad spectral progress. This study aimed to optimize the phytomediated synthesis of catalytically active, antibacterial palladium nanoparticles (PdNPs) for adsorption-based removal of ethidium bromide (EtBr) from an aqueous solution. Optimization of synthesis demonstrated that a precursor to extract ratio of 4:1, pH 3, and incubation at 80 °C for 60 min were the optimum conditions that led to the synthesis of negatively charged, highly stable, polycrystalline, spherical, and monodispersed PdNPs of 5-10 nm. When tested as catalysts, PdNPs successfully catalyzed Suzuki-Miyaura cross-coupling between aryl halides and arylboronic acids resulting in the synthesis of 4-acetylbiphenyl. Furthermore, the antibacterial activity test demonstrated that biogenic PdNPs were most effective and potent against Staphylococcus aureus and Proteus vulgaris followed by Escherichia coli, Bacillus subtilis, and Bacillus cereus. In addition, PdNPs were found as an excellent adsorbent for adsorption of EtBr from water as the adsorption reaction obeyed pseudo-second-order kinetics with a linear regression coefficient (R² > 0.995). The adsorption reaction fitted well with the Freundlich and Temkin isotherm models, indicating multi-layer adsorption. Estimating thermodynamic parameters resulted in a positive value of ΔH⁰ and ΔG⁰, demonstrating adsorption was non-spontaneous and endothermic.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534 mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248 mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.