Corncob-supported aluminium-manganese binary oxide composite enhanced removal of cadmium ions

Functional Hydrogels Promote Vegetable Growth in Cadmium-Contaminated Soil

Over the years, the concentration of cadmium in soil has increased due to industrialization. Cadmium in the soil enters the human body through plant accumulation, seriously endangering human health. In the current study, two types of hydrogels were successfully synthesized using a free radical polymerization method: an ion-type hydrogel referred to as DMAPAA (N-(3-(Dimethyl amino) propyl) acrylamide)/DMAPAAQ (N,N-Dimethyl amino propyl acrylamide, methyl chloride quaternary) and a non-ion-type hydrogel known as DMAA (N,N-Dimethylacrylamide). In the experiment carried out in this study, the ion-type hydrogel DMAPAA/DMAPAAQ was introduced to cadmium-contaminated soil for vegetable cultivation. The study found that at cadmium levels of 0 and 2 mg/kg in soil, when exposed to a pH 2 solution, cadmium wasn't detected in the filtrate using ICP. As the amount of cadmium increased to 500 mg/kg, hydrogel addition gradually reduced the filtrate cadmium concentration. Notably, the use of the 4% hydrogel resulted in 0 mg/L of cadmium. For the 0% hydrogel, vegetable cadmium absorption was determined to be 0.07 mg/g, contrasting with 0.03 mg/g for the 4% hydrogel. The DMAPAA/DMAPAAQ hydrogel significantly boosts vegetable growth by efficiently absorbing nitrate ions through ion exchange, releasing them for plant uptake. In contrast, the DMAA hydrogel, used as a control, does not enhance plant growth despite its water absorption properties. In summary, the composite hydrogel shows great potential for enhancing vegetable yield and immobilizing heavy metals in soil.

Sequestration of chromium(vi) and nickel(ii) heavy metals from unhygienic water via sustainable and innovative magnetic nanotechnology

In a stride towards sustainable solutions, this research endeavors to address the critical issue of water pollution via heavy metals by coupling the power of magnetic nanotechnology, in combination with a green chemistry approach, to eliminate two noxious inorganic pollutants: chromium(vi) and nickel(ii) from aqueous environments. The synthesis of magnetite (Fe3O4) nanoparticles was achieved using ferric chloride hexahydrate (FeCl3·6H2O) as a precursor, with the assistance of Ziziphus mauritiana Lam. leaves extract, known for its remarkable salt-reducing properties. A range of bio-adsorbents, derived from corncob biomass, corncob pyrolyzed biochar, and magnetite/corncob biochar nanocomposite (NC), were engineered for their eco-friendly and biocompatible characteristics. Extensive parametric optimizations, including variations in pH, contact time, dose rate, and concentration, were carried out to gain insights into the adsorption behavior and capacity of these bioadsorbents concerning Cr(vi) and Ni(ii). Equilibrium and kinetic studies were undertaken to comprehensively understand the adsorption dynamics. In the case of Ni(ii), the Freundlich isotherm model provided a satisfactory fit for all bio-adsorbents, demonstrating R2 values of 0.91, 0.95, and 0.96 for BM, BC, and NC, respectively. Furthermore, the pseudo 1st order model emerged as the most suitable fit for Cr(vi) sequestration in corncob BM with an R2 value of 0.98, while pseudo 2nd order models were robustly fitted for BC and NC, yielding R2 values of 0.88 and 0.99, respectively. The magnetite/corncob nanocomposite outperformed other bioadsorbents in removing heavy metals from wastewater due to its environmental friendliness, larger surface area, reusability, and cost-effectiveness at an industrial scale.

Influence of duck eggshell powder modifications by the calcination process or addition of iron (III) oxide-hydroxide on lead removal efficiency

Lead-contaminated wastewater causes toxicity to aquatic life and water quality for water consumption, so it is required to treat wastewater to be below the water quality standard before releasing it into the environment. Duck eggshell powder (DP), duck eggshell powder mixed iron (III) oxide-hydroxide (DPF), calcinated duck eggshell powder (CDP), and calcinated duck eggshell powder mixed iron (III) oxide-hydroxide (CDPF) were synthesized, characterized, and investigated lead removal efficiencies by batch experiments, adsorption isotherms, kinetics, and desorption experiments. CDPF demonstrated the highest specific surface area and pore volume with the smallest pore size than other materials, and they were classified as mesoporous materials. DP and DPF demonstrated semi-crystalline structures with specific calcium carbonate peaks, whereas CDP and CDPF illustrated semi-crystalline structures with specific calcium oxide peaks. In addition, the specific iron (III) oxide-hydroxide peaks were detected in only DPF and CDPF. Their surface structures were rough with irregular shapes. All materials found carbon, oxygen, and calcium, whereas iron, sodium, and chloride were only found in DPF and CDPF. All materials were detected O-H, C=O, and C-O, and DPF and CDPF were also found Fe-O from adding iron (III) oxide-hydroxide. The point of zero charges of DP, DPF, CDP, and CDPF were 4.58, 5.31, 5.96, and 6.75. They could adsorb lead by more than 98%, and CDPF illustrated the highest lead removal efficiency. DP and CDP corresponded to the Langmuir model while DPF and CDPF corresponded to the Freundlich model. All materials corresponded to a pseudo-second-order kinetic model. Moreover, they could be reusable for more than 5 cycles for lead adsorption of more than 73%. Therefore, CDPF was a potential material to apply for lead removal in industrial applications.

Modification of sugarcane bagasse with iron(III) oxide-hydroxide to improve its adsorption property for removing lead(II) ions

Lead contamination in wastewater results in toxicity of aquatic life and water quality, it is recommended to remove lead before discharging. Four sugarcane bagasse adsorbent materials of sugarcane bagasse powder (SB), sugarcane bagasse powder doped iron(III) oxide-hydroxide (SBF), sugarcane bagasse powder beads (SBB), and sugarcane bagasse powder doped iron(III) oxide-hydroxide beads (SBFB) were synthesized and characterized with various techniques. Their lead removal efficiencies were investigated by batch experiments on the effects of dose (0.1-0.6 g), contact time (1-6 h), pH (1, 3, 5, 7, 9, 11), and concentration (5-30 mg/L), adsorption isotherms, kinetics, and desorption experiments. All materials were amorphous phases presenting specific peaks of cellulose. SBB and SBFB detected sodium alginate peaks, and iron(III) oxide-hydroxide peaks were detected in SBF and SBFB. SB and SBF were scales or overlapping plate surfaces whereas SBB and SBFB had spherical shapes with coarse surfaces. The main functional groups of O-H, C=O, C-H, C-O, and C=C were observed in all materials, whereas Fe-O and -COOH were only found in materials with adding iron(III) oxide-hydroxide or bead material. The point of zero charges (pH_pzc) of all materials was higher than 4. The optimum conditions of SB, SBF, SBB, and SBFB with the highest lead removal efficiency at a lead concentration of 10 mg/L and pH 5 were 0.6 g and 6 h (96.08%), 0.2 g and 3 h (100%), 0.2 g and 2 h (98.22%), and 0. 1 g and 2 h (100%), respectively. Since SBFB spent less adsorbent dose and contact time than other materials with a lead removal efficiency of 100%, it was a more potential adsorbent than other materials. Thus, adding iron(III) oxide-hydroxide and changing material form helped to improve material efficiencies for lead adsorption. The maximum adsorption capacities of SB, SBF, SBB, and SBFB were 6.161, 27.027, 23.697, and 57.471 mg/L, respectively by fitting the Langmuir model. Langmuir isotherm was best fitted for SB and SBB, whereas the Freundlich model was best fitted for SBF and SBFB. The pseudo-second-order kinetic model was best fitted for all materials. Moreover, all adsorbents could be reused for more than 5 cycles with the lead removal efficiency of more than 73%. Therefore, SBFB was potential material to further apply for lead removal in industrial applications.

Ferric iron loaded porphyrinic zirconium MOFs on corncob for the enhancement of diuretics extraction

Herein, corncob waste was used as a scaffold for the fabrication of effective adsorbents. Porphyrinic zirconium metal-organic frameworks (MOFs) PCN-223 and PCN-224 constructed by different numbers of Zr6 cluster nodes were grown on the surface of the corncob. Fe (Ш) ions were implanted in the porphyrin ring by post-synthesis modification. The results showed that the extraction capacity of diuretics on PCN-224@corncob containing suitable pore size was larger than that of PCN-223@corncob. The adsorption of diuretics was further enhanced because of the electrostatic effect caused by implantation of Fe (Ш) ions. PCN-224-Fe@corncob was recyclable and selective for the extraction of furosemide (Fur) and bumetanide (Bum). Coupled in-syringe solid phase extraction (IS-SPE) with ultra-performance liquid chromatography (UPLC), an efficient, sensitive, and stable method was established. With a sensitivity between 0.6 and 1.0 μg/L and a recovery between 83.2% and 119.2%, it is used for the analysis of trace amounts of Fur and Bum in weight loss products and environmental water. The functionalized corncob has potential application for the adsorption of diuretics, and the metal ions implantation in MOFs provides a promising strategy for enhancing extraction capacity.

Effective removal of Cu(II), Pb(II) and Cd(II) by sodium alginate intercalated MgAl-layered double hydroxide: adsorption properties and mechanistic studies

To improve the adsorption efficiency of layered double hydroxides (LDHs) for heavy metals, a novel sodium alginate (SA) intercalated MgAl-LDH (SA-LDH) was synthesized in this work. SA-LDH was characterized by XRD, FTIR, XPS and employed as adsorbent for Cd(II), Pb(II), Cu(II) elimination. Adsorbent dosage, initial pH and contact time, which are regarded as several key parameters, were optimized. The results showed that SA-LDH exhibited better adsorption performance compared with the pristine MgAl-LDH. The maximum adsorption capacities of SA-LDH for Cu(II), Pb(II) and Cd(II) reached 0.945, 1.176 and 0.850 mmol/g, respectively. The possible mechanisms were analyzed by XPS, XRD and FTIR. The results showed that Cd(II), Pb(II) and Cu(II) may be removed by SA-LDH via (i) bonding or complexation with Sur-OH or Sur-O- of SA-LDH, (ii) precipitation of metal hydroxides or carbonates, (iii) isomorphic substitution, and (iv) chelation with -COO^- in the interlayers. This work provides an effective method for the development of LDH-based adsorbent and the treatment of wastewater containing heavy metals.

Effects of Mixtures of Engineered Nanoparticles and Metallic Pollutants on Aquatic Organisms

In aquatic environment, engineered nanoparticles (ENPs) are present as complex mixtures with other pollutants, such as trace metals, which could result in synergism, additivity or antagonism of their combined effects. Despite the fact that the toxicity and environmental risk of the ENPs have received extensive attention in the recent years, the interactions of ENPs with other pollutants and the consequent effects on aquatic organisms represent an important challenge in (nano)ecotoxicology. The present review provides an overview of the state-of-the-art and critically discusses the existing knowledge on combined effects of mixtures of ENPs and metallic pollutants on aquatic organisms. The specific emphasis is on the adsorption of metallic pollutants on metal-containing ENPs, transformation and bioavailability of ENPs and metallic pollutants in mixtures. Antagonistic, additive and synergistic effects observed in aquatic organisms co-exposed to ENPs and metallic pollutants are discussed in the case of “particle-proof” and “particle-ingestive” organisms. This knowledge is important in developing efficient strategies for sound environmental impact assessment of mixture exposure in complex environments.

Two-step pyrolysis of corncob for value-added chemicals and high-quality bio-oil: Effects of alkali and alkaline earth metals

Two-step pyrolysis (TSP) of corncob(CC) coupled with water and acid washing pretreatment was conducted to investigate the effects of alkali and alkaline earth metals (AAEMs) on TSP by Py-GC/MS. TG-FTIR was used to analyze the pyrolysis characteristics of the samples. The results showed that the removal of AAEMs postponed the pyrolysis process and significantly influenced the distribution of the pyrolysis products. As the content of AAEMs decreased, the bio-oil yield increased and the biochar yield decreased. TSP of CC achieved high selectivities for phenols and ketones in the first step and for hydrocarbons in the second step. TSP of acid-washed corncob (ACC) achieved high selectivities for furans in the first step and for sugars in the second step. Additionally, some value-added chemicals such as furfural (11.54%, ACC), 4-vinylphenol (23.57%, CC) and levoglucosan (43.05%, ACC) were also enriched in TSP. Therefore, a promising polygeneration scheme of TSP for the efficient utilization of biomass was proposed.