Use of horizontal subsurface flow constructed wetlands to treat reverse osmosis concentrate of rolling wastewater

<p>According to the characteristics of the reverse osmosis concentrate (ROC) generated from iron and steel company, we used three sets of parallel horizontal subsurface flow (HSF) constructed wetlands (CWs) with different plants and substrate layouts to treat the high-salinity wastewater. The plant growth and removal efficiencies under saline condition were evaluated. The evaluation was based entirely on routinely collected water quality data and the physical and chemical characteristics of the plants (<i>Phragmites australis, Typha latifolia, Iris wilsonii</i>, and <i>Scirpus planiculmis</i>). The principal parameters of concern in the effluent were chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP). The results showed that the CWs were able to remove COD, TN, and TP from ROC. <i>S. planiculmis</i> was not suitable for the treatment of high-saline wastewater. The sequence of metals accumulated in CW plants was K>Ca>Na>Mg>Zn>Cu. More than 70% of metals were accumulated in the aboveground of <i>P. australis</i>. The CW filled with gravel and manganese ore and planted with <i>P. australis</i> and <i>T. latifolia</i> had the best performance of pollutant removal, with average removal of 49.96%, 39.45%, and 72.01% for COD, TN, and TP, respectively. The effluent water quality met the regulation in China. These results suggested that HSF CW planted with <i>P. australis</i> and <i>T. latifolia</i> can be applied for ROC pollutants removal.</p

Dissolution and Absorption: A Molecular Mechanism of Mesopore Formation in Alkaline Treatment of Zeolite

With the aim to optimize alkaline treatment of zeolites to obtain hierarchical zeolites, dissolution and absorption mechanisms relevant to mesopore formation were investigated at an atomistic scale by density functional calculations. In the dissolution processes, dealumination is energetically more favorable than desilication, though both processes can occur. The dissolved Al species prefer to be absorbed back onto zeolite surfaces whereas the dissolved Si species tend to aggregate in solution. The dissolution process promotes but the absorption process hampers the mesopore formation, laying foundation for understanding the mesoporosity influenced by the variations of zeolite framework and solution

Origin of Dirac Cones in SiC Silagraphene: A Combined Density Functional and Tight-Binding Study

The formation of Dirac cones in electronic band structures via isomorphous transformation is demonstrated in 2D planar SiC sheets. Our combined density functional and tight-binding calculations show that 2D SiC featuring C–C and Si–Si atom pairs possesses Dirac cones (DCs), whereas an alternative arrangement of C and Si leads to a finite band gap. The origin of Dirac points is attributed to bare interactions between Si–Si bonding states (valence bands, VBs) and C–C antibonding states (conduction bands, CBs), while the VB–CB coupling opens up band gaps elsewhere. A mechanism of atom pair coupling is proposed, and the conditions required for DC formation are discussed, enabling one to design a class of 2D binary Dirac fermion systems on the basis of DF calculations solely for pure and alternative binary structures