Synthesis, characterization, process optimization, and techno-economic study on the production of Co-Al layered double hydroxide nanoparticles

Layered double hydroxides (LDHs) have been widely explored for their unique structures and diverse functionalities. In this work, Co-Al LDHs were synthesized at different operating conditions (i.e., different reaction time and temperature) using the co-precipitation (CP) and low-temperature (below 100°C) hydrothermal (LTHT) methods. The properties of the synthesized materials were tested using various characterization techniques such as X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and optical methods (UV-Diffuse Reflectance Spectroscopy (UV-DRS), Photoluminescence (PL), Fluorescence (FL) Spectroscopy) and Raman Spectroscopy to evaluate structural, chemical bonding, functional group identification, morphological, optical properties and photocatalytic potential. Results show that co-precipitation, with a longer reaction time, resulted in higher product yield, while low-temperature hydrothermal had a temperature-dependent yield and produced LDH of higher purity. The multi-criteria decision-making (MCDM) method, including TOPSIS, SAW, and GRA, was used to determine the optimal synthesis conditions based on yield, quality, and cost. Based on the selection criteria and assigned criteria weightage, co-precipitation (CP) with a 16-hour reaction time is selected as the optimal choice. Techno-economic analysis performed using Aspen Plus reported that co-precipitation offers an annual sales revenue of $53.25 million with a capital cost of $3.21 million, annual operating expenses of $17.25 million due to lower energy requirements. The study also compares the effect of product sales prices on profit margin (pre- and post-taxes), annual cash flow, and payback period, providing insights into the financial feasibility of the scaled-up LDH production.