Adsorption/Desorption Capability of Potassium-Type Zeolite Prepared from Coal Fly Ash for Removing of Hg2+

Column study using modified banana pseudo stem as adsorbent for removal of Pb (II)

Eco-friendly adsorbents such as banana pseudo stem play a fundamental role in the removal of heavy metal elements from the wastewater. Key water resources and chemical industries have been encountering difficulties in removing heavy metal elements using existing conventional methods. The lead-removal process is currently a challenging task for environmental scientists and engineers in terms of cost, effluent disposal, and safety concerns. Hence, this work demonstrates the adsorption of Pb (II) onto modified banana pseudo stem (MBPS) powder as a potential adsorbent to treat different effluents. A characterization of modified banana pseudo-stem powder was performed using scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy which confirms the material. Experiments carried out using a column process for the removal of lead (II) from an aqueous solution at a fixed concentration of 50 ppm, pH 6 and contact time 120 min. The BET surface area of MBPS was found to be 7.27 m²/g. The results showed that the column studies explain better performance for the removal of Pb (II) and the maximum removal was found to be 49% at lower flow rate (5 mL/min) of fixed initial concentration of 50 ppm.

Zeolite greenly synthesized from fly ash and its resource utilization: A review

Fly ash is an incineration byproduct of thermal power plants. Due to the complex composition of fly ash, improper disposal will seriously harm the ecological environment. Therefore, how to effectively use fly ash to safely and environmentally replace landfills is a worldwide concern. Considering the high silicon and aluminum contents in fly ash, it has the potential to synthesize zeolite, which has a wide range of applications in sewage treatment, gas adsorption, etc. Therefore, the synthesis of zeolites from fly ash is consistent with the theme of sustainable development. The synthesis mechanism of zeolite, various synthetic methods of zeolite from fly ash and their advantages and disadvantages was introduced in detail. In addition, combined with the current research hotspots, the application of synthetic zeolite from fly ash in the fields of sewage treatment and gas adsorption was introduced. Finally, the future development prospects and research directions of synthetic zeolite from fly ash to improve the utilization rate of fly ash were considered.

Selective adsorption of Hg(ii) with diatomite-based mesoporous materials functionalized by pyrrole-thiophene copolymers: condition optimization, application and mechanism

A novel diatomite-based mesoporous material of MCM-41/co-(PPy-Tp) was prepared with MCM-41 as carrier and functionalized with the copolymer of pyrrole and thiophene. The physicochemical characteristics of the as-prepared materials were characterized by various characterization means. The removal behaviour of Hg(ii) was adequately investigated via series of single factor experiments and some vital influence factors were optimized via response surface methodology method. The results exhibit that diatomite-based materials MCM-41/co-(PPy-Tp) has an optimal adsorption capability of 537.15 mg g-1 towards Hg(ii) at pH = 7.1. The removal process of Hg(ii) onto MCM-41/co-(PPy-Tp) is controlled by monolayer chemisorption based on the fitting results of pseudo-second-order kinetic and Langmuir models. In addition, the adsorption of Hg(ii) ions onto MCM-41/co-(PPy-Tp) is mainly completed through forming a stable complex with N or S atoms in MCM-41/co-(PPy-Tp) by electrostatic attraction and chelation. The as-developed MCM-41/co-(PPy-Tp) displays excellent recyclability and stabilization, has obviously selective adsorption for Hg(ii) in the treatment of actual electroplating wastewater. Diatomite-based mesoporous material functionalized by the copolymer of pyrrole and thiophene exhibits promising application prospect.

Improvement in adsorption of Hg2+ from aqueous media using sodium-type fine zeolite grains

To increase the adsorption capability of Hg²⁺ from aqueous media, we prepared sodium-type fine zeolite grains with various particle sizes (denoted as ZE1, ZE2 and ZE3). The particle sizes of ZE1, ZE2 and ZE3 were 16.363 ± 0.365, 1.454 ± 0.357 and 0.607 ± 0.377 μm, respectively. Moreover, the CEC, specific surface area and pore volume were in the order ZE1 (42 mmol/g and 23.5 m²/g) < ZE2 (72 mmol/g and 67.1 m²/g) < ZE3 (135 mmol/g and 176.6 m²/g). Subsequently, the Hg²⁺ adsorption capability was investigated. The performance of tested agents on Hg²⁺ adsorbed was in the order ZE1 (5.0 mg/g) < ZE2 (9.4 mg/g) < ZE3 (20.2 mg/g). It was concluded that fine crystalline zeolite was important in enhancing the adsorption capability of Hg²⁺. In addition, the mechanism of adsorption of Hg²⁺ on the ZE samples was evaluated. Our results suggested that Hg²⁺ was exchanged with sodium ions in the interlayers of ZE samples with correlation coefficients of 0.966-0.979. Our findings revealed that these ZE samples constitute potential agents for the adsorption of Hg²⁺ from aqueous media.