Cerium oxide‑cadmium oxide nanomaterial as efficient extractant for yttrium ions

Adsorptive removal of heavy metals and organic dyes by sodium alginate/coffee waste composite hydrogel

Heavy metals and dyes used in technological applications have a detrimental influence on human health and the environment. The most used methods for removing pollutants depend on high-cost materials. Therefore, this research was conducted on cost-effective alternatives derived from natural resources and food waste. Herein, we designed a composite hydrogel based on sodium alginate/coffee waste (Alg/coffee) as adsorbent for the removal of organic and inorganic pollutants from aquatic solutions. The selectivity study displayed that Alg/coffee is more effective in adsorbing Pb(II) and acridine orange dye (AO). Adsorption of Pb(II) and AO was studied at concentration range of 0-170 mgL-1 and 0-40 mgL-1. Adsorption data of Pb(II) and AO reveals their fitting to Langmuir-isotherm and pseudo-second-order-kinetic models. The findings demonstrated that Alg/coffee hydrogel are more effective than coffee powder itself with an adsorption (%) approaching 98.44 % of Pb(II) and 80.53 % of AO. Real sample analysis reveals the efficiency of Alg/coffee hydrogel beads in Pb(II) adsorption. The adsorption cycle was examined four times providing high efficiency toward Pb(II) and AO. Desorption of Pb(II) and AO was easily performed using HCl eluent. Thus, Alg/coffee hydrogel beads could be promising adsorbent for the removal of organic and inorganic pollutants.

Selective adsorption of iron(III) ions based on nickel(II) oxide-copper(II) oxide nanoparticles

Background:

Water contamination and its remediation are currently considered a major concern worldwide. Design of effective methods for water purification is highly demanded for adsorption and removal of such pollutants.

Objective:

This study depicts the effectiveness of nickel oxide-copper oxide nanoparticles (NiO-CuO), which can extract and remediate ferric ions, Fe (III), from aqueous solutions.

Methods:

The NiO-CuO nanoparticles were simply prepared by the co-precipitation method and then used as adsorbent with respectable advantages of high uptake capacity and surface area.

Results:

Adsorption of Fe(III) onto NiO-CuO nanoparticles showed an uptake capacity of 85.86 mgg−1 at pH 5.0. The obtained data from the carried-out experiment of Fe (III) adsorption onto NiO-CuO nanoparticles were well suited to the Langmuir isotherm and pseudo-second-order kinetic models. Moreover, different coexisting ions did not influence the adsorption of Fe(III) onto NiO-CuO nanoparticles. The recommended methodology was implemented on the adsorption and removal of several environmental water samples with high efficiency.

Conclusion:

The design method displayed that NiO-CuO nanoparticles can be used as promising material for the adsorptive removal of heavy metals from water.

Copper Oxide-Antimony Oxide Entrapped Alginate Hydrogel as Efficient Catalyst for Selective Reduction of 2-Nitrophenol

Copper oxide-antimony oxide (Cu₂O-Sb₂O₃) was prepared and entrapped inside Na-alginate hydrogel (Alg@Cu₂O-Sb₂O₃). The developed Alg@Cu₂O-Sb₂O₃ was used as catalytic reactor for the reduction of 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), congo red (CR), acridine orange (AO), methylene blue (MB) and potassium ferricyanide (K₃[Fe(CN)₆]). Alg@Cu₂O-Sb₂O₃ was found to be selective and more efficient for the reduction of 2-NP among all the pollutants. Therefore, 2-NP was selected for a detailed study to optimize various parameters, e.g., the catalyst amount, reducing agent concentration, 2-NP concentration and recyclability. Alg@Cu₂O-Sb₂O₃ was found to be very stable and easily recyclable for the reduction of 2-NP. The Alg@Cu₂O-Sb₂O₃ nanocatalyst reduced 2-NP in 1.0 min, having a rate constant of 3.8187 min⁻¹.

Fabrication and characterization of chitosan-CeO2-CdO nanocomposite based impedimetric humidity sensors

Nanocomposites of chitosan and cerium oxide‑cadmium oxide (CeO₂-CdO) nanopowder were developed to fabricate impedimetric humidity sensors. The low temperature-stirring was used to synthesize CeO₂-CdO nanopowder. Average particle size of synthesized nanopowder was 100 ± 20 nm. Various composition of chitosan-CeO₂-CdO nanocomposites were developed using echo-friendly (mechanical mixing) technique. Pellets of 13.0 mm diameter and 1.0 ± 0.1 mm thickness were prepared using hydraulic press under the pressure of 375 MPa. Silver paste was used to deposit the electrodes; the length of each electrode was 12.0 mm and the gap between two electrodes was 2.0 ± 0.5 mm. The mechanism of sensing is based on impedimetric change in response to humidity variation. Fabricated sensors showed high sensitivities ranging from -930.0 kΩ/%RH to -2091.1 kΩ/%RH. Response and recovery times are up to 1 s, while the humidity sensing range is 5 to 95%RH. The fabricated sensors are very attractive to use in several devices for environmental monitoring and biomedical applications.

Sodium alginate nanocomposite based efficient system for the removal of organic and inorganic pollutants from wastewater

An effective and selective catalytic system based on cerium oxide-stannous oxide (CeO₂-SnO) wrapped Na-alginate hydrogel was developed for the selective reduction of potassium ferricyanide (K₃[Fe(CN)₆]). Na-alginate hydrogel was used as a reacting container for CeO₂-SnO nanoparticles. Na-alginate wrapped CeO₂-SnO (Alg/CeO₂-SnO) was applied as a catalyst and examined toward the reduction of several hazardous pollutants, such as nitrophenols, dyes and K₃[Fe(CN)₆]. Alg/CeO₂-SnO nanocatalyst was mostly selective toward K₃[Fe(CN)₆] since it was more effective and economical for reduction of K₃[Fe(CN)₆]. Further different parameters like catalyst amount, reducing agent amount, K₃[Fe(CN)₆] concentration and recyclability were optimized. The increase in both nanocatalyst amount and NaBH₄ concentration resulted in increasing the rate of the catalytic reduction of K₃[Fe(CN)₆]. Alg/CeO₂-SnO nanocatalyst reduced K₃[Fe(CN)₆] in 4.0 min with a reaction rate constant of 0.9114 min^-1. The nanocatalyst can be easily recovered by pulling the hydrogel from the reaction medium up to four cycles. Alg/CeO₂-SnO nanocatalyst was also examined in real samples like irrigation water, sea water, well water, university water, which was effective for K₃[Fe(CN)₆] reduction by 95.16%-96.54%. This novel approach provides a new catalyst for efficient removal of K₃[Fe(CN)₆] from real samples and can be a time and cost alternative tool for environmental safety.

Super adsorption performance of carboxymethyl cellulose/copper oxide-nickel oxide nanocomposite toward the removal of organic and inorganic pollutants

A novel nanocomposite bead based on polymeric matrix of carboxymethyl cellulose and copper oxide-nickel oxide nanoparticles was synthesized, characterized, and applied for adsorptive removal of inorganic and organic contaminants at trace level of part per million (mgL^-1) from aqueous sample. Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) adsorbent beads were selective toward the removal of Pb(II) among other metal ions. The removal percentage of Pb(II) was more than 99% with 3 mgL^-1. The waste beads after Pb (II) adsorption (Pb@CMC/CuO-NiO) and CMC/CuO-NiO nanocomposite beads were employed as adsorbents for removing of various dyes. It was found that Pb@CMC/CuO-NiO can be reused as adsorbent for the removal of Congo Red (CR), while CMC/CuO-NiO nanocomposite beads were more selective for removal of Eosin Yellow (EY) from aqueous media. The adsorption of CR and EY was optimized, and the removal percentages were 93% and 96.4%, respectively. The influence of different parameters was studied on the uptake capacity of Pb(II), CR, and EY, and lastly, the CMC/CuO-NiO beads exhibited responsive performance in relation to pH and other parameters. Thus, the prepared CMC/CuO-NiO beads were found to be a smart material which is effective and played super adsorption performance in the removal of Pb(II), CR, and EY from aqueous solution. These features make CMC/CuO-NiO beads suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial adsorbents.

Development of alginate@tin oxide-cobalt oxide nanocomposite based catalyst for the treatment of wastewater

In this study, tin oxide‑cobalt oxide nanocatalyst was prepared by a simple method, which grew in spherical particles with an average diameter of 30 nm. Tin oxide-cobalt oxide was further wrapped in alginate polymer hydrogel (Alg@tin oxide-cobalt oxide), and both materials were utilized as nanocatalysts for the catalytic transformation of different pollutants. Tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts were tested for the catalytic reduction of 4-nitrophenol, congo red, methyl orange, methylene blue (MB) and potassium ferricyanide in which sodium borohydride was used as a reducing agent. Tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts synergistically reduced MB in shorter time (2.0 and 4.0 min) compared to other dyes. The reduction conditions were optimized by changing different parameters. The rate constants for MB reduction were calculated and found to be 1.5714 min^-1 and 0.6033 min^-1 using tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts, respectively. Implementing Alg@tin oxide-cobalt oxide nanocatalyst toward MB reduction in real samples proved its efficacy in sea and well water samples. The catalyst could be easily recovered, recycled and revealed a minimal loss of nanoparticles, which offering a competition and replacement with reputable commercial catalysts.

Adsorptive removal of lanthanum based on hydrothermally synthesized iron oxide-titanium oxide nanoparticles

Iron oxide-titanium oxide (Fe₂O₃-TiO₂) nanoparticles were developed as an effective adsorbent in order to extract and remove lanthanum ions selectively from aqueous media. Fe₂O₃-TiO₂ nanoparticles were prepared by simple hydrothermal method and structurally characterized using FESEM, EDS, XRD, FTIR, and BET techniques. The analytical potential of Fe₂O₃-TiO₂ nanoparticles was interpreted by applying the kinetic and isotherm models. The maximum static uptake capacity was 89.63 mgg^- 1 at pH 7. Adsorption isotherm data evinced that a monolayer adsorption occurred on a homogeneous adsorbent surface which is compatible with Langmuir isotherm model. Data acquired from kinetic models study proved that La (III) adsorption onto Fe₂O₃-TiO₂ nanoparticles followed a pseudo-second-order kinetic equation. Thermodynamic study exhibited that a spontaneous process is favorable for adsorption mechanism of La (III) on Fe₂O₃-TiO₂ nanoparticles. Moreover, the existence of different coexisting ions did not influence the extraction of La (III). Finally, the recommended methodology was applied on several environmental samples.