Separation of mercury (II) ions from aqueous solution using zeolite-P composite membrane developed on low cost tubular ceramic support

Mercury, emitted from various industries, is toxic and has devastating environmental consequences. Therefore, it becomes imperative to monitor the levels of mercury closely. This work mainly focuses on preparing inexpensive zeolite-coated kaolin membranes for separating Hg²⁺ from water. The membrane support was prepared using kaolin (50 wt%), quartz (25 wt%), and calcium carbonate (25 wt%). This mixture was blended with a 3 % hydroxypropyl methylcellulose (HPMC) solution and then passed through an extruder to obtain tubular support, which was further sintered at 950 °C. The zeolite-coated membrane (ZP membrane) was fabricated by subjecting the sintered support to a 48-h hydrothermal synthesis in 7 Na₂O: 1 Al₂O₃: 10 SiO₂: 205H₂O gel at 90 °C. The isoelectric point of the ZP membrane was estimated to be 4.5. The zeolite-coated membrane displayed a pure-water permeability of 22.7 × 10⁻⁹ m³/m² s kPa, a porosity of 31.72 ± 0.86 %, and a pore size of 90 nm. The performance of the ZP membrane in separating the Hg²⁺ ion from an aqueous solution was investigated by pressure variations (69–345 kPa) and feed concentration (0.5–10 ppm). The results clearly showed that in all cases, the zeolite-P membrane exhibited more than 99 % rejection of Hg²⁺ ions from aqueous solutions during the filtration experiments. Thus, the prepared ZP membrane can effectively be used for the separation of Hg²⁺ ions from wastewater.