The removal of Pb(II), Cd(II), Cu(II), and Zn(II) from aqueous solutions using (un)modified Serbian interstratified montmorillonite/kaolinite clay as an adsorbent was investigated. The clay was modified by mechanochemical activation for different time periods. X-ray diffraction patterns and particle size distributions were used to characterize the samples. Batch adsorption studies were conducted to optimize various conditions. The adsorption equilibrium was established within 60 min, and the maximum adsorption occurred in the pH range of 4.5–6.5. The milled clays exhibited greater equilibrium adsorption capacities (q e) for all of the metals than the raw clay. A difference in q e values for clays milled for 2 and 19 h could be observed only for initial concentrations (C i) of ≥100 mg dm–3. This was related to the amorphization (i.e., exfoliation) of 19-h-milled clay particles. The adsorption equilibrium data of heavy metals on both raw and modified clays fit the Langmuir equation, although there were changes in the microstructure of the clay. The mechanochemical treatment of the clay reduced the amount of adsorbent necessary to achieve a highly efficient removal of heavy metals by a factor of 5. Thus, the mechanochemically treated interstratified clay can be considered as an efficient adsorbent for the simultaneous removal of divalent heavy metals.

Mechanically activated carbonized rayon fibers as an electrochemical supercapacitor in aqueous solutions, Electrochimica Actahttp://dx.

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Many water utilities, particularly in the developing countries, continue to operate inefficient water distribution systems (WDSs) with a significant amount of water and revenue losses. Various factors, manageable to different extents, contribute to water losses, such as poor infrastructure, high pressures, illegal water use, etc. Whilst the problem of water losses in WDSs is global in scale, solutions need to be tailored to local circumstances due to the various causes of water loss and the mechanisms available to manage them. This paper investigates the potentials of the available pressure management methodologies and their implementation in developing countries, using a case study of a district metering area (DMA) in Kotež-Serbia. The minimal night flow method was applied for assessment of real losses. A particular focus is on assessment of water savings due to reduction of pressures. A total of three methods for estimation of water savings are described and tested against data measured in the DMA under initial and reduced pressures: (i) the method based on Leakage Index (LI) calculations, (ii) the PRESMAC model and (iii) a newly-developed method which is based on the assumption that both leakage and consumption are pressure dependent. The results indicate that the third method leads to the most accurate prediction of the total amount of water savings under reduced pressures, with only 6% difference between measured and estimated volume of saved water.