Nanocomposites composed of polyacrylamide and nanoclay were synthesized via free-radical cross-linking polymerization and used to adsorb Co 2+ and Ni 2+ ions from water. The polyacrylamide (PAM)/sodium montmorillonite (Na-MMT) nanocomposites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy to confirm the interaction between montmorillonite and the polymer matrix. The effects of pH and heavy metal ion concentration on the adsorption capacity of PAM/Na-MMT were evaluated to determine suitable operating conditions for further experiments. Batch adsorption experimental data were fitted to Langmuir and Freundlich models, which provided information about the adsorption mechanism and the adsorbent surface. The highest Ni 2+ removal yield was found to be 99.3% using the 2:1 (w/w) nanocomposite at pH 6 in 100 ppm of Ni 2+ solution. The Co 2+ removal yield was 98.7% at pH 6 in 60 ppm of Co 2+ solution using the 4:1 (w/w) nanocomposite. These results were higher than those obtained by polyacrylamide and nanoclay under the same conditions (removal yield between 87.40 and 94.50%), indicating that PAM/Na-MMT nanocomposites remove heavy metal water pollutants more efficiently and can be used as a novel adsorbent for further industrial applications.

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BackgroundThe production of photocatalytic nanoparticles such as TiO2 has received increasing interest for biomedical and wastewater treatment applications. However, the conventional synthesis of such materials faces several environmental concerns.MethodsIn this work, green synthesis is addressed to prepare TiO2 nanoparticles at large scale using Lemongrass (Cymbopogon citratus) and titanium isopropoxide (TTIP). This process was designed and modeled using computer-aided process engineering (CAPE) in order to obtain the extended mass/energy balances, as well as operating parameters. Process simulation was carried out using the commercial software Aspen Plus®. In addition, energy performance of large-scale nanoparticle production was analyzed to identify alternatives for process improvement from an exergetic point of view.ResultsThe production capacity of the plant was estimated as 1,496 t/y of TiO2 nanoparticles by the conversion of 32,675 t/y lemongrass and 5,724 t/y TTIP. Hence, the overall production yield is 0.26 kg TiO2/kg TTIP. Exergy analysis reported an overall exergy efficiency of 0.27% and an exergy loss of 159,824.80 MJ/h. These results suggest that such a process requires the implementation of process improvement strategies to reach a more sustainable design from energy and thermodynamic viewpoints.

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The process design and technology selection are driven by multiple objectives including technical, economic, environmental, safety, and resilience drivers. Traditionally, technoeconomic analyses have been used to select and optimize the process design. Subsequently, environmental, safety, and resilience issues have been included in post-design analysis. With the recognition of the importance of including various objectives during the early stages of the process design, there has been a growing interest in the development of systematic methods for the multi-objective conceptual design. Recently, novel concepts have been proposed for the incorporation of sustainability and safety in designs through financial frameworks. In the current work, an extended approach is proposed for the incorporation of reliability, resilience, safety, and sustainability aspects during the conceptual design of the process system. In this proposed methodology, safety and sustainability weighted return on investment metric (SASWROIM) is extended to include impacts of resilience and reliability aspects with different design changes and configurations. For this purpose, a safety, sustainability, reliability, and resilience weighted return on investment metric (S2R2WROIM) is introduced. Multi-objective decision-making can thus be carried out for the optimal design based on this augmented method over the convention economic return on investment metric. The general methodology to screen process alternatives through S2R2WROIM begins with the synthesis and simulation of base case and alternative case flowsheet in Aspen HYSYS. This is followed by performance analysis, evaluation of various metrics, and applications of integrated metric to select the recommended design. A compressor process system case study in a hydrocracking process plant is demonstrated to illustrate the applications and benefits of the proposed methodology. The new approach provides decision makers with meaningful information and insights about safety, reliability, resilience, and sustainability along with the economic aspect.