Elemental mercury (Hg0) removal from coal syngas using magnetic tea-biochar: Experimental and theoretical insights

Mercury is ranked 3^rd as a global pollutant because of its long persistence in the environment. Approximately 65% of its anthropogenic emission (Hg⁰) to the atmosphere is from coal-thermal power plants. Thus, the Hg⁰ emission control from coal-thermal power plants is inevitable. Therefore, multiple sorbent materials were synthesized using a one-step pyrolysis method to capture the Hg⁰ from simulated coal syngas. Results showed, the Hg⁰ removal performance of the sorbents increased by the citric acid/ultrasonic application. T5CUF_0.3 demonstrated the highest Hg⁰ capturing performance with an adsorption capacity of 106.81 µg/g within 60 min at 200 °C under complex simulated syngas mixture (20% CO, 20% H₂, 10 ppmV HCl, 6% H₂O, and 400 ppmV H₂S). The Hg⁰ removal mechanism was proposed, revealing that the chemisorption governs the Hg⁰ removal process. Besides, the active Hg⁰ removal performance is attributed to the high dispersion of valence Fe₃O₄ and lattice oxygen (α) contents over the T5CUF_0.3 surface. In addition, the temperature programmed desorption (TPD) and XPS analysis confirmed that H₂S/HCl gases generate active sites over the sorbent surface, facilitating high Hg⁰ adsorption from syngas. This work represented a facile and practical pathway for utilizing cheap and eco-friendly tea waste to control the Hg⁰ emission.     

Effect of Flow Depth and Velocity on Nitrate Loss Rates in Natural Channels1

Carleton, James N. and Yusuf M. Mohamoud, 2012. Effect of Flow Depth and Velocity on Nitrate Loss Rates in Natural Channels. Journal of the American Water Resources Association (JAWRA) 1‐12. DOI: 10.1111/jawr.12007 Abstract: Loss rates of nitrate from streams and rivers are governed by movement of the ion from water column to anoxic bed sediments. Quantitative representations of nitrate in streams and rivers have often treated such losses as governed by first‐order mechanisms that are invariant with respect to potential modulating factors other than temperature. Results of studies in recent years, however, suggest that rates of water column‐sediment mass transfer are influenced by stream geometry and associated hydraulics. We develop expressions for the instream nitrate loss rate coefficient, k, as a function of water velocity and depth, using hydraulic geometry to empirically relate velocity to depth for two cases: (1) variability in mean conditions among reaches; and (2) temporal variability in conditions at a single reach, under changing flow. The result is expressions for k as functions of water column depth. Measured stream k values reported in the literature are shown to be well represented by expressions developed for the first case, and the potential for application to probabilistic analysis is briefly examined. We explore the latter case using the Hydrologic Simulation Program – FORTRAN (HSPF) model, modified to incorporate the dependence of k on instantaneous stream depth. In example simulations of two nitrate‐exporting watersheds, the incorporation of depth‐dependence of k produces improvement in the model’s ability to match observed stream nitrate concentrations.     

Bioreactor applications in waste treatment

An overview of bioreactor applications in treatment of gaseous, liquid and solid wastes is presented with emphasis on newer technologies. Waste treatment is considered in a broad context including concentration by bioaccumulation, degradation to substances with reduced environmental impact and upgrading to such useful products as feeds, foods and fuels. Biofilters and bioscrubbers for gaseous pollutants, high-rate municipal and industrial wastewater treatment in airlift bioreactors, reactor-based soil bioremediation, artificial wetland filters for liquid effluents, and protein enrichment of agricultural solid residues are some of the technologies reviewed. The various treatment strategies are illustrated with examples. The developments discussed point to an increasing role for bioreactor based processes in waste treatment and reuse.     

A GIS-based model for rating natural protection areas according to natural protection priorities

There has been a major urban shift of population in Turkey over the last century. Most people lived in rural areas until 1960, but now more than half live in urban areas. This trend has continued over the last 20 years, as families moved further away from city centres to find houses in the country, and this has caused land use to change rapidly. In decision-making studies to protect nature areas, rating and assessment of ecological data by scientific verification is difficult due to the huge volume and diversity of data. Therefore, the search for the most suitable and applicable method to achieve physical planning based on ecological understanding has been sought. The necessity for numerous parameters to be taken into account has stimulated the use of geographic information systems (GIS). This study assesses the usefulness of a GIS-based model in the protected area of Kaynaklar County, to the south of the city of Izmir. Existing cultural and natural land-use types, as well as soil, hydrologic, geologic and geomorphologic data layers (future classes) were gathered from field observation and using Landsat and IKONOS satellite images, and transferred to a database according to GIS rules. Index values were determined by taking impact on attributes of natural protection as a priority and these were attached to each feature class. Layers of data were merged by spatial intersection methods and new polygons were created for both cultural and natural features. A three-grade final map of the study area was generated using total index values of each new polygon.     

Recent developments on gas–solid heterogeneous oxidation removal of elemental mercury from flue gas

Environmental Chemistry Letters - Mercury is a toxic and persistent environmental pollutant which has been recognized as a global threat to human health and our ecosystem because mercury...     

Heavy Metal Levels in Biota and Sediments in the Northern Coast of the Marmara Sea

Concentration of Cd, Co, Cr, Ni, Zn, Fe, Mn, Pb and Cu were determinedin biota and sediment samples collected from the Marmara Sea in Turkey. The levels of Zn, Fe, Mn, Pb and Cu in the macroalgae are higher than previous studies in the Marmara Sea. Moreover, Cu and Zn concentrations at the present study are significantly high than Bosphorus and Black Sea algae. The order heavy metal concentrations in the mussel samples was: Fe > Zn > Ni > Mn > Cu > Pb > Cr > Cd > Co. The metal concentrations are generally lower when compared with the Black Sea mussels except Pb. At the same time, concentrations of Pb, Cu and Zn in the mussel species are lower when compared with the results in the Aegean Sea. The ranges of Mn and Cu in the tested fish samples are higher than Black Sea fish. On the other hand, Cd, Co, Cr, Zn and Pb concentrations are lower. The northern coast of the Marmara Sea having the highest metal concentrations in sediments as follows: Co, Cr, Ni, Fe at ?arköy ; Pb, Cu at M. Ere?li; Cd, Zn, Mn at Menek?e. The heavy metal levels in the sediment samples are lower than other areas in the Marmara Sea.     

Energy recovery from municipal solid waste in Nigeria and its economic and environmental implications

An assessment of potential biomass resources in Nigeria for the production of methane and power generation is presented in this paper. Nigeria, as an underdeveloped and populous country, needs an uninterrupted source of energy. The country's energy problems have crippled large sectors of the economy. The percentage of people connected to the national grid is 40%. These 40% experience electricity supply failure on average 10–12 hours daily. Energy generation from municipal solid waste (MSW) is an effective MSW management strategy. Yearly waste generation has increased from 6,471 gigagrams (Gg) in 1959 to 26,600 Gg in 2015. This amount is projected to reach 36,250 Gg per year by 2030. Methane emission for 2015 was 491 Gg, and it is projected to reach 669 Gg in 2030. These values translate to 3.48 × 10⁹ kilowatt hours (kWh) of electricity for 2015, with a projected 4.74 × 10⁹ kWh by 2030. The revenue to be derived from the electricity that is generated could have been US$365.04 × 10⁶ for 2015, and it is estimated that it will reach US$473.82 × 10⁶ by 2030. It was found that methane emissions from MSW increased with time, and capturing this gas for energy production will lead to a sustainable waste management.     

Correction to: Sustainable development goals assessment of Erzurum province with SWOT‑AHP analysis

Environment, Development and Sustainability -