Recent advancements in g-C3N4-based photocatalysts for photocatalytic CO2reduction: A mini review

© 2020 The Royal Society of Chemistry. Carbon dioxide (CO2) is a very important micro-molecular resource. Using CO2 captured from the atmosphere for high-output synthesis of chemicals as raw materials has great significance and potential for various industrial applications. Since the industrial revolution in the 18th century, manmade CO2 emission has increased by 45%, which negatively impacts the planetary climate by the so-called greenhouse effect. Therefore, high-efficiency photocatalysis and photocatalysts for CO2 conversion have become the most important challenges and milestones throughout the world. In consideration of this, various catalysts have been explored. Among these, graphitic carbon nitride (g-C3N4) as a semiconductor is emerging as a highly promising photocatalyst for removing CO2 from the atmosphere. Moreover, due to its excellent chemical stability and unique band structure, g-C3N4 has exhibited significant application potential for photocatalysis. This review summarizes the advancements that have been made in the synthesis and photocatalytic applications of g-C3N4-based catalysts for CO2 reduction in recent years and explains the future challenges and prospects in this vital area of research

Removal of Hg(II) in aqueous solutions through physical and chemical adsorption principles

Adsorption has been the focus of research on the treatment of heavy metal mercury pollution since it is among the most toxic heavy metals in existence. The US EPA has set a mandatory discharge limit of 10 μg Hg L-1 for wastewater and for drinking water a maximum accepted concentration of 1 μg Hg L-1. Physical adsorption and chemical adsorption are the two major mechanisms of adsorption methods used for mercury removal in aqueous sources. The recent decades\u27 research progress is reviewed to elaborate varieties of adsorption materials ranging from materials with large surface area for physical adsorption to metal oxides for chemical adsorption. Many examples are presented to illustrate the adsorption principles and clarify the relationship between the structure and performance of the adsorbents. The combination of physical adsorption and chemical adsorption gives rise to numbers of potential mercury removal composites. This review demonstrates the adsorption mechanism and the performance of varieties of adsorbents, which would provide a comprehensive understanding on the design and fabrication of new materials for the removal of heavy metal ions in water

1.31 IMPLEMENTATION AND EFFECTIVENESS OF NON-SPECIALIST MEDIATED INTERVENTIONS FOR CHILDREN WITH ASD: A SYSTEMATIC REVIEW AND META-ANALYSIS

Objectives: The task shifting of ASD to nonspecialist-mediated interventions has been suggested as a cost-effective way to ensure accessible care for all populations. This meta-analysis rates the quality of evidence presented in a RCT assessing the effectiveness of nonspecialist-mediated interventions for ASD. Methods: Eight electronic databases were searched for the RCT of nonspecialized mediated interventions for youth with a clinical diagnosis of ASD and no restrictions on age, gender, language, socioeconomic status, or time period. The quality of studies was assessed using the Cochrane tool. The meta-analytical data were rated for quality using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) criteria. The outcomes included in the meta-analysis were those reported in ≥2 studies. Heterogeneity was defined at a cutoff value of ≥40 percent and was based on its extent; data were pooled together with fixed or random effects. For outcomes reported in ≥10 studies, a meta-regression analysis established potential moderators of intervention effects. Results: We selected 33 RCTs for our predetermined eligibility criteria. With various interventions used, there was a significant improvement in communication, motor and social skills, and the parent-child relationship. The Cochrane tool revealed a low risk of bias among the studies. According to GRADE criteria, the ratings varied from very low to high. There were notably high ratings for communication, language and motor skills, moderate ratings for adaptive behaviors, the severity of symptoms, receptive language, social skills, and improvement in the parent-child relationship. The analysis revealed no impact of varying density of dosages on the effectiveness of interventions. Methodological heterogeneity was found because of differences in diagnosis criteria, study strategies, and intervention mediators, which is considered an important limitation. Conclusions: The meta-analysis showed that the interventions given by nonspecialists were effective across varying outcomes, improved the parent-child relationship, and lowered stress for parents. This analysis favors the implementation of nonspecialist-mediated interventions for youth with ASD in a cost-effective manner

Surface Modification of TFC-PA RO Membrane by Grafting Hydrophilic pH Switchable Poly(Acrylic Acid) Brushes

The grafting of pH-responsive poly(acrylic acid) (PAA) brushes was carried out on the surface of a commercial TFC-PA membrane using surface-initiated atom transfer radical polymerization (SI-ATRP). Poly(t-butyl acrylate) was polymerized through the SI-ATRP method followed by its acid hydrolysis to form PAA hydrophilic polymer brushes. Surface morphology, permeation flux, salt rejection, and pore sizes were investigated. The contact angle for water was reduced from 50° for a pristine membrane to 27° for the modified membrane due to a modification with the hydrophilic functional group and its brush on membrane surfaces. The flux rate also increased noticeably at lower pH values relative to higher pH for the modified membranes, while the flux remains stable in the case of pristine TFC-PA membranes. There is slight transition in the water flux rate that was also observed when going from pH values of 3 to 5. This was attributed to the pH-responsive conformational changes for the grafted PAA brushes. At these pH values, ionization of the COOH group takes place below and above pKa to influence the effective pore dimension of the modified membranes. At a lower pH value, the PAA brushes seem to permit tight structure conformation resulting in larger pore sizes and hence more flux. On the other hand, at higher pH values, PAA brushes appeared to be in extended conformation to induce smaller pore sizes and result in less flux. Further, pH values were observed to not significantly affect the NaCl salt rejection with values observed in between 98.8% and 95% and close to that of the pristine TFC-PA membranes. These experimental results are significant and have immediate implication for advances in polymer technology to design and modify the “switchable membrane surfaces” with controllable charge distribution and surface wettability, as well as regulation of water flux and salt

Graphene Oxide-PES-Based Mixed Matrix Membranes for Controllable Antibacterial Activity against Salmonella typhi and Water Treatment

The present work is focused on preparation, characterization, and antibacterial activity evaluation of graphene oxide/polyethersulfone mixed matrix filtration membranes. Graphene oxide (GO) was synthesized via improved Hummer’s method and characterized by XRD, FTIR, and SEM. FT-IR spectra showed the presence of carboxylic acid and hydroxyl groups on GO nanosheets. Different concentrations of the synthesized GO at 0.25, 0.5, and 1.0 wt. % were incorporated in polyethersulfone (PES) matrix via phase inversion method to fabricate GO-PES membranes. Increasing porosity and formation of wider, finger-like channels were observed with increased GO concentrations relative to pristine membranes as evident from scanning electron microscopy (SEM) micrographs of the fabricated membranes. However, membranes prepared with 1 wt. % GO appear to contain aggregation and narrowing of pore morphology. GO-incorporated membranes demonstrated enhanced flux, water-retaining capacities, and wettability as compared to pristine PES membranes. Shake flask and colony counting methods were employed to carry out antibacterial testing of synthesized GO and fabricated GO-PES membranes against Salmonella typhi (S. typhi)—a gram-negative bacteria present in water that is known as causative agent of typhoid. Synthesized GO showed significant reduction up to 70.8% in S. typhi cell count. In the case of fabricated membranes, variable concentrations of GO are observed to significantly influence the percentage viability of S. typhi, with reduction percentages observed at 41, 60, and 69% for 0.25, 0.5, and 1.0 wt. % GO-incorporated membranes relative to 17% in the case of pristine PES membranes. The results indicate a good potential for applying GO/PES composite membranes for water filtration application

Estimation of Potential Soil Erosion and Sediment Yield: A Case Study of the Transboundary Chenab River Catchment

Near real-time estimation of soil loss from river catchments is crucial for minimizing environmental degradation of complex river basins. The Chenab river is one of the most complex river basins of the world and is facing severe soil loss due to extreme hydrometeorological conditions, unpredictable hydrologic response, and complex orography. Resultantly, huge soil erosion and sediment yield (SY) not only cause irreversible environmental degradation in the Chenab river catchment but also deteriorate the downstream water resources. In this study, potential soil erosion (PSE) is estimated from the transboundary Chenab river catchment using the Revised Universal Soil Loss Equation (RUSLE), coupled with remote sensing (RS) and geographic information system (GIS). Land Use of the European Space Agency (ESA), Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data, and world soil map of Food and Agriculture Organization (FAO)/The United Nations Educational, Scientific and Cultural Organization were incorporated into the study. The SY was estimated on monthly, quarterly, seasonal, and annual time-scales using sediment delivery ratio (SDR) estimated through the area, slope, and curve number (CN)-based approaches. The 30-year average PSE from the Chenab river catchment was estimated as 177.8, 61.5, 310.3, 39.5, 26.9, 47.1, and 99.1 tons/ha for annual, rabi, kharif, fall, winter, spring, and summer time scales, respectively. The 30-year average annual SY from the Chenab river catchment was estimated as 4.086, 6.163, and 7.502 million tons based on area, slope, and CN approaches. The time series trends analysis of SY indicated an increase of 0.0895, 0.1387, and 0.1698 million tons per year for area, slope, and CN-based approaches, respectively. It is recommended that the areas, except for slight erosion intensity, should be focused on framing strategies for control and mitigation of soil erosion in the Chenab river catchment.Water Resource