Nanomaterials and Nanotechnology in Wastewater Treatment

Rapid incorporation of gold nanoparticles onto graphene oxide-polymer nanofiber membranes for photothermally-accelerated water purification

This work demonstrates the rapid coating of gold nanoparticles (AuNPs) onto electrospun composite polyacrylonitrile (PAN) nanofibers containing a large amount of graphene oxide (GO) and reduced graphene oxide (rGO) for photothermally-driven applications. A modification of GO with a cationic surfactant greatly improves its loading efficiency into the PAN nanofibers, and the subsequent hydrazine treatment readily converts the integrated GO into rGO. Rapid loading of AuNPs onto these membranes results in measurably higher photothermal heating characteristics than the pristine PAN, GO-PAN, and rGO-PAN membranes under a solar-simulated light source. The light-induced heating properties are then utilized in the removal of organic dyes in an aqueous solution. While the GO-PAN and rGO-PAN membranes remove the dyes via physical adsorption, the AuNP-loaded membranes show an additional catalytic decomposition process, resulting in detectably faster removal rates. The degradation of the organic dyes is accelerated under a solar simulated light source due to the light-enhanced heating and photocatalytic properties of the integrated AuNPs. The ability to maximize the dual properties of these membranes can greatly reduce toxic organic pollutants, which can lead to the development of practical water purification systems under sunlight irradiation.

Cu-Enhanced Efficient Förster Resonance Energy Transfer in PBSA Sunscreen-Associated Ternary Cu x Cd1-x S Quantum Dots

Quantum dots (QDs) are semiconducting nanocrystals that exhibit size- and composition-dependent optical and electronic properties. Recently, Cu-based II-VI ternary Cu _x Cd_1-x S (CCS) QDs have emerged as a promising class of QDs as compared to their binary counterparts (CuS and CdS). Herein, a series of ternary CCS QDs are synthesized by changing the molar concentration of Cu²⁺ ions only keeping the 1:1 ratio of the stoichiometric mixture of Cd²⁺ and S^2-. These CCS QDs are attached to 2-phenylbenzimidazole-5-sulfonic acid (PBSA), an eminent UV-B filter widely used in many commercial sunscreen products to avoid skin erythema and DNA mutagenic photolesions. The photoinduced Förster resonance energy transfer (FRET) is investigated from PBSA to CCS QDs as a function of Cu concentration in CCS QDs using the steady-state photoluminescence and time-resolved photoluminescence measurements. A 2-fold increase in the magnitude of non-radiative energy transfer rate (K _T(r)) is observed as the molar concentration of Cu in CCS QDs increases from 2 to 10 mM. Our findings suggest that in PBSA-CCS QD dyads, the FRET occurrence from PBSA to QDs is dictated by the dynamic mode of photoluminescence (PL) quenching. The bimolecular PL quenching rate constants (k _q) estimated by Stern-Volmer's plots for PBSA-CCS QD dyads are of the order of 10¹⁰ M^-1 s^-1, which signifies that in the PBSA-CCS QD dyad FRET system, the process of PL quenching is entirely diffusion-controlled.

Cosmetic wastewater treatment technologies: a review

Over the past three decades, environmental concerns about the water pollution have been raised on societal and industrial levels. The presence of pollutants stemming from cosmetic products has been documented in wastewater streams outflowing from industrial as well as wastewater treatment plants. To this end, a series of consistent measures should be taken to prevent emerging contaminants of water resources. This need has driven the development of technologies, in an attempt to mitigate their impact on the environment. This work offers a thorough review of existing knowledge on cosmetic wastewater treatment approaches, including, coagulation, dissolved air flotation, adsorption, activated sludge, biodegradation, constructed wetlands, and advanced oxidation processes. Various studies have already documented the appearance of cosmetics in samples retrieved from wastewater treatment plants (WWTPs), which have definitely promoted our comprehension of the path of cosmetics within the treatment cycle; however, there are still multiple blanks to our knowledge. All treatments have, without exception, their own limitations, not only cost-wise, but also in terms of being feasible, effective, practical, reliable, and environmentally friendly.