Kokkinos Evgenios, Chousein Chasan, Simeonidis Konstantinos, Coles Sandra, Zouboulis Anastasios, Mitrakas Manassis
Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
Materials (Basel). 2020 Apr 9;13(7):1762. doi: 10.3390/ma13071762.
The surface configuration of tetravalent manganese feroxyhyte (TMFx) was appropriately modified to achieve higher negative surface charge density and, hence, to improve its efficiency for the removal of dissolved Cd and Pb mostly cationic species from water at pH values commonly found in surface or ground waters. This was succeeded by the favorable engagement of Ca cations onto the surface of a mixed Mn-Fe oxy-hydroxide adsorbent during the preparation step, imitating an ion-exchange mechanism between H and Ca; therefore, the number of available negatively-charged adsorption sites was increased. Particularly, the calcium coverage can increase the deprotonated surface oxygen atoms, which can act as adsorption centers, as well as maintain them during the subsequent drying procedure. The developed Ca-modified adsorbent (denoted as TMFx-Ca) showed around 10% increase of negative surface charge density, reaching 2.0 mmol [H]/g and enabling higher adsorption capacities for both Cd and Pb aquatic species, as was proved also by carrying out specific rapid small-scale column tests, and it complied with the corresponding strict drinking water regulation limits. The adsorption capacity values were found 6.8 μg·Cd/mg and 35.0 μg·Pb/mg, when the restructured TMFx-Ca adsorbent was used, i.e., higher than those recorded for the unmodified material.
对四价锰水铁矿（TMFx）的表面构型进行了适当改性，以实现更高的负表面电荷密度，从而提高其在地表水或地下水中常见pH值下从水中去除溶解的镉和铅（主要是阳离子物种）的效率。这是通过在制备步骤中使钙阳离子良好地结合到混合锰铁羟基氧化物吸附剂的表面来实现的，这类似于H和Ca之间的离子交换机制；因此，增加了可用的带负电荷吸附位点的数量。特别是，钙覆盖可以增加去质子化的表面氧原子，这些氧原子可以作为吸附中心，并在随后的干燥过程中保持它们。所开发的钙改性吸附剂（表示为TMFx-Ca）的负表面电荷密度增加了约10%，达到2.0 mmol [H]/g，并使对镉和铅水生物种具有更高的吸附容量，通过进行特定的快速小规模柱试验也证明了这一点，并且它符合相应严格的饮用水法规限值。当使用重组后的TMFx-Ca吸附剂时，吸附容量值分别为6.8 μg·Cd/mg和35.0 μg·Pb/mg，即高于未改性材料的记录值。
