Tausif Ahmad

Removal of heavy metal ions (HMI) from water streams is desirable due to their toxic and carcinogenic effects. Therefore, this study was conducted to prepare a low cost adsorbent in the form of non-activated carbon (NAC) and activated carbon (AC) using rice husk, a local bio-waste material. Activation of material was performed by base leaching, chemical activation using ZnCl2, followed by acid washing. The initial and final concentrations of HMI in water were measured using Atomic Absorption Spectroscopy. Volatile matter, ash, moisture and surface area of the prepared material were measured using ASTM methods E 897- 88 R04, E 830 - 87 R04, E 949 - 88 R04 and D 1050 - 1 respectively. An enhancement factor was used to evaluate the activating effect of the adsorbent. Maximum % age removal of HMI was measured as 69.0, 64.0, 62.0 and 56% for Ni, Cd, Zn and Pb respectively using NAC. However, by using AC, a significant increase in the %age removal efficiency of HMI was observed and measured as 99.0, 95.5, 93.0 and 89% for Ni, Cd, Zn and Pb respectively. The results showed that AC derived from waste biomass is a simple, ecological and cost-effective approach to remove bulk of metal ions from water and wastewater.

Background: The removal of persistent organic pollutants (POPs) from the contaminated water by employing photocatalytic adsorption is considered as one of the most emerging technologies due to its’ cost- and energy-effectiveness. It has attracted significant attention of global researchers to process the world’s wastewater. Methods: Among different adsorbents, the metal-organic frameworks (MOFs) have demonstrated remarkable potential and a bright future perspective in the photocatalytic-based adsorptive removal of POPs from wastewater. This review deals with the introduction of MOFs and contaminations in wastewater, followed by the synthesis method for MOFs and their properties. The review is extended to the review of mechanisms for the photocatalytic adsorption along with the recent progress in removal of persistent toxic substances, pesticides, herbicides, phenols, and antibiotics. Furthermore, the future challenges in this promising area are also discussed. Results: Much research work has been done in the area of photocatalytic adsorptive removal of the POPs using the MOFs due to their significant structural and texture properties. Substantial research efforts have been carried out to functionalize the MOFs in order to improve their adsorption potential. Overall, this review demonstrated that the MOFs could be applied successfully for the photocatalytic adsorptive removal of the POPs from contaminated water. Conclusion: Despite the bright future perspective of the MOFs, there are some issues that need to be accounted for: The development of MOFs with redox-active metals and/or organic functionalized ligands, MOFs application for the photocatalytic adsorptive removal of the gaseous contaminants, indepth understanding of the mechanism of the photocatalytic adsorptive removal of the POPs, and the application of the MOFs for photocatalytic adsorptive removal of the POPs in real environmental conditions. The fast development of the MOFs in the recent era indicates a bright future perspective in spite of the challenges in this area.

Phytosynthesis of gold nanoparticles (AuNPs) has achieved an indispensable significance due to the diverse roles played by biomolecules in directing the physiochemical characteristics of biosynthesized nanoparticles. Therefore, the precise identification of key bioactive compounds involved in producing AuNPs is vital to control their tunable characteristics for potential applications. Herein, qualitative and quantitative determination of key biocompounds contributing to the formation of AuNPs using aqueous Elaeis guineensis leaves extract is reported. Moreover, roles of phenolic compounds and flavonoids in reduction of Au³⁺ and stabilization of AuNPs have been elucidated by establishing a reaction mechanism. Fourier‐transform infrared spectroscopy (FTIR) showed shifting of O─H stretching vibrations toward longer wavenumbers and C═O toward shorter wavenumbers due to involvement of polyphenolic compounds in biosynthesis and oxidation of polyphenolic into carboxylic compounds, respectively, which cape nanoparticles to inhibit the aggregation. Congruently, pyrolysis–gas chromatography–mass spectrometry revealed the major contribution of polyphenolic compounds in the synthesis of AuNPs, which was further endorsed by reduction of total phenolic and total flavonoids contents from 48.08 ± 1.98 to 9.59 ± 0.92 mg GAE/g and 32.02 ± 1.31 to 13.8 ± 0.97 mg CE/g within 60 Min, respectively. Based on experimental results, reaction mechanism explained the roles of phenolic compounds and flavonoids in producing spherical‐shaped AuNPs.