Occurrence of phthalates in facemasks used in India and its implications for human exposure.

Synthetic polymers with additives are used in the manufacturing of face masks (FMs); hence, FMs could be a potential source of exposure to phthalic acid esters (PAEs). India stands second in the world in terms of the FMs usage since the beginning of Covid-19 pandemic. However, little is known about the PAEs content of FMs used in India. Some PAEs, such as DEHP and DBP are suspected endocrine disrupting chemicals (EDCs); hence, wearing FM may increase the risk of exposure to these EDCs. In this study, we collected 91 samples of FMs from eight Indian cities and analyzed for five PAEs viz. DMP, DEP, DBP, BBP, and DEHP. The PAEs contents in FMs ranged from 101.79 to 27,948.64 ng/g. The carcinogenic risk of N 95 with filter, N-95, and cloth masks was higher than the threshold levels. The findings indicate the need to control PAEs in FMs through regulatory actions.

Leaching characteristics and hazard evaluation of bottom ash generated from common biomedical waste incinerators.

India has more than 202 biomedical waste incinerators, however, knowledge on the chemical characteristics of incinerator ash is lacking. The objective of this study was to evaluate the lecahablility characteristics of bottom ash and to study the levels of incineration by-products viz. polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Bottom ash samples from 13 common biomedical waste treatment facilities (CBMWTF) were colleted and subjected to leachig test, sequential extraction procedure (SEP) and PAHs and PCBs analysis. Among metals, cadmium, chromium, manganese, lead and zinc were found higher than the regulatory limits indicating its hazardous nature. SEP showed that substantial fraction of Cd (30%) and Zn (25%) were associated with leachable fractions, whereas metals such as Cr, Fe, Mn, and Ni were mainly associated with reducible, organics and residual fractions. Concentrations of USEPA 16 priority PAHs ranged between 0.17-12.67 mg kg-1 and the total toxic equivalents (TEQ) were in the range of 0.9-421.9 ng TEQ/g. PAHs with 4-rings dominated all the samples and accounted for 68% to total PAHs concentrations. Concentration of Σ19 PCB congeners ranged from 420.4 to 724.3 µg kg-1. PCBs homologue pattern was dominated by mono- to tetra chlorinated congeners (60-86%). The findings indicate the need for segregation of plastics from biomedical waste, improvement of combustion efficiency, and efficient air pollution control devices for the existing incinerators in CBMWTFs.

Powdered silk: A promising biopolymer for the treatment of dye contaminated water.

Discharge of textile dye effluents into water bodies is creating stress to aquatic life and contaminating water resources. In this study, a new biopolymer adsorbent silk fibroin (SF) was prepared from Bombyx mori silk fibroin (SF) and used for removal of Solochrome Black-T (SB-T) from water. This innovative adsorbent exhibits an exceptional adsorption capacity of 20.08 mg/g, achieving a removal efficiency of approximately 98.6 % within 60 min. Notably, the powdered SF adsorbent demonstrates rapid kinetics, surpassing the performance of previously reported similar adsorbents in adsorption capacity and reaction speed. The molecular weight and particle diameter of the material were observed to be > 1.243 kDa and 3 µm, respectively. The experimental investigations were performed on different parameters, viz., adsorbent dosage, contact time, repeatability, and desorption-adsorption study. The experimental data well fit for the Langmuir model (R2 = 0.937, qmax = 20.08 mg/g) and the pseudo-second-order kinetics (R2 = 0.921 and qe = 1.496 mg/g). Compared to the adsorbents reported in the literature, the newly prepared SF showed high adsorption capacity and faster kinetics to address real-life situations. The novelty of this work extends beyond its remarkable adsorption capabilities. The SF adsorbent offers a cost-effective, sustainable solution and regenerable adsorption material with minimal negative environmental impacts. This regenerability, with its versatility and broad applicability, positions powdered SF fibroin as a transformative technology in water treatment and environmental protection.

Nanophotonics triggered thermally enhanced solar water disinfection bottles for slum dwellers.

Among several existing technologies, solar pasteurization is widely accepted as a reliable and cost-effective method for the removal of microbial pathogens from water. This work reports nanophotonics-triggered thermally enhanced solar water disinfection bottles (nano-SODIS) designed rationally by coating plasmonic carbon nanoparticles (CNP) on the outer surface for the targeted pathogen inactivation from water. The cost-effective CNP nanophotonic material used in this work has high efficiency in harvesting solar radiation and dissipating the heat locally. It has broad absorption efficiency to cover the entire solar spectrum; hence, it is capable to generate multiple scattering. It has also properties of boosting of photon absorption and focusing the light within a constrained spatial region, resulting in powerful and targeted heating that inactivates microorganisms in near proximity. These CNPs were used to coat the nano-SODIS water bottles that achieved the highest temperature of 65-70 °C within 90 min of exposure to solar radiation with a consequent six-log reduction. The disinfection period was reduced by a factor of 3 compared to the conventional solar disinfection system. The treated water was further assessed for 7 days, which confirmed the complete absence of bacteria and no sign of regeneration after storing for a longer period. The SODIS bottles coated with CNP thus overcome the problem of limited solar absorption by acquiring higher broadband absorption potential and thus achieving comparatively high disinfection efficiency. The broad band absorption of CNP was confirmed through UV-DRS absorption spectra. The nano-SODIS bottles designed and constructed in this work are simple, durable, and user friendly in nature and have been deployed in the rural and slums areas of Nagpur, Delhi, and Mumbai, India to provide pathogen-free potable water and to improve the health of local poor communities.

Silk fibroin: a promising bio-material for the treatment of heavy metal-contaminated water, adsorption isotherms, kinetics, and mechanism.

Silk is the strongest natural biopolymer produced by silk worms possessing superior adsorbent properties and thus extensively used in various applications. The present study involved the preparation of powder form of a silk fibroin materials and their application in adsorption of heavy metals, particularly, iron from aqueous solution. The morphological and structural characteristic properties of this promising materials were examined by using different analytical techniques. Batch experiments were conducted within feasible parametric ranges to understand the effect of dose, time, concentration, pH, and reusability. Silk fibroin was effective for iron adsorption over a wide range of pH 6 to 10. The adsorption removal efficiency of 98% was attained for removal of iron from contaminated water at moderate dose of 0.25 g and contact time of 60 min, which is unprecedented by considering the environment benign nature of the material. The data was examined in different isotherm models wherein it fitted best in Langmuir adsorption model. Similarly, Langmuir isotherm model, with R2 value of 0.984 and KL 0.412 and maximum adsorption capacity as 12.82 mg g-1, suggests monolayer adsorption. Kinetic study with better R2 value of 0.941 represented the pseudo-second order kinetics governed by the chemisorption reaction. To understand the practical applicability of silk fibroin, the repeatability study up to 5 cycles were performed. The findings are very encouraging which confirmed the usage of silk fibroin as adsorbent for multiple cycles with marginal decrease in adsorption efficiency. Eventually, the material was tested for iron removal in real contaminated water which revealed its potential and selectivity for removal of iron in different matrix.

Biomimetic lipophilic activated carbon for enhanced removal of triclosan from water.

Triclosan, an antimicrobial micro-pollutant with a high bio-accumulation potential represented by its high octanol-water partition coefficient (log Kow) of 4.76 is commonly encountered in water and wastewater worldwide. The present study focuses on biomimetic surface modification of commercial activated carbon (PAC) with long chain fatty acid namely docosahexaenoic acid (DHA) resulting in enhanced affinity for the hydrophobic micro-pollutant; triclosan (TCS). The sorption process of the resulting modified lipophilic carbon (PACM) was investigated for the effect of various experimental conditions. The Freundlich isotherm and pseudo-second-order kinetic models had a better fit. PACM exhibited the maximum adsorption capacity of 395.2 mg g-1 in contrast to 71.5 mg g-1 obtained for PAC. The surface morphology in terms of surface area, surface acidity, pore size, contact angle, etc. and were also evaluated. The contact angle of 134.3° obtained for PACM confirmed its highly hydrophobic nature. The efficacy of PACM was also evaluated using real-world secondary treated effluent containing triclosan confirming its applicability for tertiary treatment of wastewater. The study established that the biomimetic approach of creating lipid-like sites on the carbon surface results in the enhanced removal of lipophilic micro-pollutants. It can also be utilized for the removal and recovery of a wide variety of other organic micro-pollutants.

Effect of hydrophobicity of pharmaceuticals and personal care products for adsorption on activated carbon: Adsorption isotherms, kinetics and mechanism.

Adsorption of three pharmaceuticals and personal care products (PPCPs), namely caffeine, ibuprofen and triclosan on commercial powdered activated carbon was examined in aqueous medium. The contaminants were chosen based on their diverse log Kow (octanol-water partition coefficient) viz. - 0.07 for caffeine, 3.97 for ibuprofen and 4.76 for triclosan to examine the role of hydrophobicity on adsorption process. The adsorbent characterisation was achieved using BET surface area, SEM, pore size distribution studies and FTIR. Influence of mass of PAC, contact time, solution pH and initial concentration on adsorption capacity of PAC was studied. Adsorption isotherms and kinetics were applied to establish the mechanism of adsorption. The kinetics followed pseudo-second order with physisorption occurring through particle diffusion. The Freundlich model fitted best among the isotherm models. The adsorption capacity increased in the order CFN < IBU < TCS which correlates with increasing hydrophobicity (log Kow), molecular weight and decreasing water solubility, respectively. We conclude that micro-pollutant hydrophobicity contributes towards adsorption on activated carbon.