Enhanced removal of multiple metal ions on S-doped graphene-like carbon-supported layered double oxide: Mechanism and DFT study

Effective adsorptive removal of Pb2+ ions from aqueous solution using functionalized agri-waste biosorbent: New green mediation via Seidlitzia rosmarinus extract

Currently, the use of natural adsorbent for the elimination of pollutants, such as heavy metals, from water has been extensively investigated. However, the low adsorption capacity of these natural adsorbents has led researchers towards the use of synthetic surfactants, which themselves can become environmental pollutants. In this research, an investigation was conducted to examine the impact of a surfactant obtained from the Seidlitzia rosmarinus plant on the adsorption properties of Pumpkin seed shell (PSS), a natural adsorbent. As a result, a modified version of PSS, known as functionalized Pumpkin seed shell (FPSS), was developed, and the effect of these two adsorbents on the elimination of Pb2+ has been investigated. FESEM, EDS, FTIR, and BET analyses were conducted to get detailed information of the adsorbent. Additionally, the effects of contact time, dosage of the adsorbent, pH of the solution, and temperature on the adsorbent were studied. The experimental data was fitted using Langmuir, Freundlich, Temkin, and Jovanovic isotherms. The PSS adsorbent was fitted best with the Langmuir isotherm, showing an adsorption capacity of 160.80 mg g-1, while the FPSS adsorbent was fitted with the Jovanovic isotherm, exhibiting an adsorption capacity of 553.57 mg g-1. Furthermore, kinetic modeling results indicated that the data for these adsorbents follow pseudo-second-order kinetic. Finally, the impact of coexisting ions and reusability was examined, with the FPSS adsorbent outperforming PSS. Therefore, the investigation of all these aspects demonstrated that the use of this natural surfactant significantly improves the performance of the adsorbent.

Doping matters in carbon nanomaterial efficiency in environmental remediation

Carbon nanomaterials (CNMs) are rapidly emerging in materials science research due to their widespread environmental applications. They are useful for environmental pollutants' remediation through various methods. Heteroatom doping resulted in reliable approaches to overcome pristine CNMs challenges. The engineering of the dopants is believed to be a promising route to improve the efficiency of CNMs in environmental remediation. The idea of doping has been attractive since it allows the control of electronic properties due to the electron transfer between dopants and the host material and the dopants along with the bonding between analogous atoms and carbon atoms. This mini-review, through computational and experimental studies, puts special emphasis on the role of doping different CNMs as an efficient approach to enhance the environmental remediation.

Effective adsorption of Pb(ii) from wastewater using MnO2 loaded MgFe-LD(H)O composites: adsorption behavior and mechanism

Pb(ii) adsorption by MnO₂/MgFe-layered double hydroxide (MnO₂/MgFe-LDH) and MnO₂/MgFe-layered metal oxide (MnO₂/MgFe-LDO) materials was experimentally studied in lab-scale batches for remediation property and mechanism analysis. Based on our results, the optimum adsorption capacity for Pb(ii) was achieved at the calcination temperature of 400 °C for MnO₂/MgFe-LDH. Langmuir and Freundlich adsorption isotherm models, pseudo-first-order and pseudo-second-order kinetics, Elovich model, and thermodynamic studies were used for exploring the Pb(ii) adsorption mechanism of the two composites. In contrast to MnO₂/MgFe-LDH, MnO₂/MgFe-LDO_{400 °C} has a stronger adsorption capacity and the Freundlich adsorption isotherm model (R² > 0.948), the pseudo-second-order kinetic model (R² > 0.998), and the Elovich model (R² > 0.950) provide great fits to the experimental data, indicating that the adsorption occurs predominantly via chemisorption. The thermodynamic model suggests that MnO₂/MgFe-LDO_{400 °C} is spontaneously heat-absorbing during the adsorption process. The maximum adsorption capacity of MnO₂/MgFe-LDO_{400 °C} for Pb(ii) was 531.86 mg g^-1 at a dosage of 1.0 g L^-1, pH of 5.0, and temperature of 25 °C. Through characterization analysis, the main mechanisms involved in the adsorption process were precipitation action, complexation with functional groups, electrostatic attraction, cation exchange and isomorphic replacement, and memory effect. Besides, MnO₂/MgFe-LDO_{400 °C} has excellent regeneration ability in five adsorption/desorption experiments. The above results highlight the powerful adsorption capacity of MnO₂/MgFe-LDO_{400 °C} and may inspire the development of new types of nanostructured adsorbents for wastewater remediation.

Utilization of nitrogen, sulfur co-doped porous carbon micron spheres as bifunctional electrocatalysts for electrochemical detection of cadmium, lead and mercury ions and oxygen evolution reaction

The development of high-performance bifunctional electrocatalysts for oxygen evolution reaction and heavy metal ion (HMI) detection is significant and challenging. Here, a novel nitrogen, sulfur co-doped porous carbon sphere bifunctional catalyst was designed and fabricated by hydrothermal followed by carbonization using starch as carbon source and thiourea as nitrogen, sulfur source for HMI detection and oxygen evolution reactions. Under the synergistic effect of pore structure, active sites and nitrogen, sulfur functional groups, C-S_0.75-HT-C₈₀₀ demonstrated excellent HMI detection performance and oxygen evolution reaction activity. Under optimized conditions, the detection limits (LODs) of C-S_0.75-HT-C₈₀₀ sensor were 3.90, 3.86 and 4.91 nM for Cd²⁺, Pb²⁺ and Hg²⁺ when detected individually; and the sensitivities were 13.12, 19.50 and 21.19 μA/μM. The sensor also obtained high recoveries of Cd²⁺, Hg²⁺ and Pb²⁺ in river water samples. During the oxygen evolution reaction, a Tafel slope of 70.1 mV/dec and a low overpotential of 277 mV were obtained for C-S_0.75-HT-C₈₀₀ electrocatalyst with a current density of 10 mA/cm² in basic electrolyte. This research offers a neoteric and simple strategy in the design as well as fabrication of bifunctional carbon-based electrocatalysts.