Synthesis of carbon-based nanocatalysts with tuned surface sites, well-exposed catalytic sites, and enhanced efficiency of mass transfer is necessary for activating peroxymonosulfate (PMS) into reactive oxygen species (ROS) to remove organic contaminants. In our research, a series of N and cobalt codoped mesoporous dendritic carbon (CoX/NMDC-Y, where X=0.033, 0.02, 0.015, 0.01 Co/Si molar ratio and Y is the pyrolysis temperature) as PMS catalysts were synthesized via single-step hydrothermal process, and used for degrading BPA and other organic pollutants (methyl orange, rhodamine B, phenol, and sulfamethoxazole) for the first time. The Co0.02/NMDC-700 /PMS system showed high catalytic efficiency in a wide pH range. Under selected experimental conditions (PMS=0.7mM, Co0.02/NMDC-700=0.2g L−1, pH=8.2), degradation of BPA in the Co0.02/NMDC-700/PMS, Co0.02/MDS-700/PMS, only PMS, and NMDC-700/PMS systems reached approximately 100%, 81%, 21%, and 29%, respectively. Likewise, 0.3 mg L−1Co was leached in the Co0.02/NMDC-700/PMS process. The morphology, structure, and catalytic efficiency of Co0.02/NMDC-700 were well-preserved after recycling. Using EPR and organic scavengers depicted that SO4•−, •OH, 1O2, and O2•− were generated from PMS activation. The XPS, in-situ ATR-FTIR, and electrochemical analyses were used to investigate the mechanism of PMS activation. The high degradation efficiency was assigned to better textural characteristics, well-exposed catalytic sites due to dendritic morphology, diffusion-friendly structure, and synergistic effect of Co and N and ROS. Our proposed research may give insights into employing other metals (Fe, Mn, Cu, and their composite) incorporated in NMDC for PMS activation and other areas of AOPs.
The separation and recovery of useful organics from wastewater have been a promising alternative to tackling water pollution and resource shortages, while strategies that truly work have rarely been explored. Herein, a reversible CO2 triggered sol–gel state transformation mediated selective organics uptake-release system using a surface modified carbonitride (S-CN) is proposed and exhibits remarkable organics recovery performance from wastewater. Results show that CO2 can serve as a cross-linker for linking S-CN particles to form a hydrogel by electrostatic interaction and hydrogen bonding, which can be recycled to the pristine sol state simply by removing the cross-linked CO2 with Ar purging. The reversible sol–gel transformation achieves nearly complete uptake of valuable organics from wastewater with high selectivity at the first sol-to-gel stage through electrostatic interaction, hydrogen bonding, and π–π interactions together, and it recovers 90% of the organics uptaked by releasing them into a concentrated solution at the second gel-back-to-sol stage.
2 Abstract: The Cholistan rangelands were observed to be degrading due to various stresses, whose effects could be seen as poor livestock production. Hence a preliminary survey was conducted in order to assess the nutrients concentration of major browses used as feed during the period of whole year for livestock grazing therein. The browse species were evaluated by their mineral composition including the macro minerals (P, K, Na, Ca and Mg) and micro minerals (Mn, Cu, Zn and Fe). The investigated species were consisting of Calligonum polygonoides, Suaeda fruticosa, Salsola baryosma, Haloxylon recurvum, Haloxylon salicornicum, Capparis decidua, Calotropis procera, Tamarix aphylla, Prosopis cineraria and Acacia nilotica. The browse samples were collected based on preferences by grazing animals, accessibility to browsing and abundance in the said area. The results of this study indicated that the concentration of almost all the minerals (micro and macro) except Na among selected browses was less than required level for ruminants grazing therein. This may be, one of the causes responsible for the pitiable health and productivity of livestock in Cholistan rangelands. The low quality forages require the attention of range manger to improve the habitat conditions and livestock breeds. It was proposed that fertilization of soil and vegetation with additional sources will not only improve the over all vegetation but also enhance the productivity of grazing animals and other wildlife. These rangelands have potential for improvement provided proper ecological management practices and with participation of local community.
An economical and environment-friendly material as a catalyst is highly desirable to activate peroxymonosulfate (PMS) into reactive oxygen species (ROS). Cobalt-doped dumbbell-shaped manganese oxide (CoX˗MnOx where X = 1.0, 6.0, 12.0, 18.0, and 24.0 mM) was synthesized as a PMS-activator for degrading organic pollutants in wastewater. We have developed a green, facile, and low-temperature route without any organic solvents, and templates to synthesize Co-doped dumbbell-shaped MnOx with hierarchical porosity. It is the first-ever research to use these materials for peroxymonosulfate activation. The microstructure contained nanoparticles that self-assembled into a maze-like dumbbell-shaped mesostructure. Phenol degradations after 9 min of Co18-MnOx/PMS, MnOx/PMS, Co3O4/PMS, PMS, and adsorption were 100%, 27%, 33%, 17%, and 5%, respectively. The Co18-MnOx morphology, microstructure, textural properties, and catalytic efficiency were well-retained after recycling. Compared to SO4·− and ·OH, 1O2 and O2·− were the dominant ROS. The balance among redox couples of different species (Co2+/Co3+, Mn3+/Mn4+, O2−/O2) and PMS decomposition enabled ROS production. The high catalytic activity was assigned to the Mn/Co synergism, hierarchical microstructure, and ROS. Furthermore, the DFT study investigated the difference between the activation mechanism of PMS (adsorption and electron transfer) on MnOx and Co-MnOx surfaces. Our research devised a facile procedure to synthesize other transition metals doped MnOx for advanced oxidation processes and multipurpose applications.
Soil samples at 0-20 cm depth were collected from major crop areas of Hindukush mountainous range, District Chitral, extreme Northwestern Pakistan, during April 2014 to assess their physico-chemical properties and spatial distribution pattern. 103 soil samples were analyzed and maps were created by geostatistical technique of inverse distance weighting and kriging techniques using GIS and GS win-7 computer software. The soil texture ranged from silt loam to dominantly sandy loam, slightly acidic to alkaline and moderate to highly calcareous but with no salinity indication. Soil organic matter was higher than 2 % in about 75 % of samples. Soil pH, EC and lime showed slight dependence on each other with r values from 0.4 to 0.5 while OM varied independently as indicated by their lower correlation values. Semivariogram analysis showed that soil pH, lime, OM had strong spatial dependence (nugget-sill ratio, <25%) while silt, sand, EC had moderately (nugget-sill ratio, 25-75%) and clay had weakly distributed in the area. Linear, Gaussian and exponential models were used for different soil parameter based on nugget, mean prediction error and root mean square standardize prediction error values and maps were developed through extension techniques to cover all the area outside the sampling points.
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