Technological advancement has increased people's standard of living, but environmental pollution has concomitantly gone up severalfold to the extent of even beyond natural repair. Many measures are continuously being taken to combat pollution, yet the problem persists and assumes serious proportions in the form of discernible global warming and heavily contaminated waterbodies. Current research focuses on sustainable solutions to environmental remediation using naturally occurring, inexpensive, and non-hazardous clay minerals. The binding, adsorptive, and catalytic properties of clay minerals applied in environmental pollution control is the focus of the current study.
The binding property of clay was explored in shaping the vegetal based activated carbon powder into cylindrical pellets. A mixture design approach was used to create formulations of binders and carbon. Empirical correlations for strength, capacity, and cost objectives were developed in terms of statistically significant variables. The optimal blends of binders and carbon that maximized strength, adsorption capacity, and minimized cost were identified.
Next, the adsorptive efficacy of the clay was investigated. The swelling nature of clay upon hydration varied the pore volume, and the material hence lacks permanent pore volume. This was addressed by pillaring the clay. Pillaring is a process through which bulky polycations are intercalated into the clay matrix. In the current work, chromium polycations were used as a pillaring agent. The synthesis steps of pillared clays were intensified by reducing the processing times for intercalation and pillaring using ultrasound. The physicochemical properties of the pillared clay could be easily tuned to cater for the dye wastewater treatment application. The anionic Acid Blue 74 and the cationic Basic Orange 2 dyes were employed to explore the adsorption performance of Cr pillared clay (CrPC). In addition to kinetic, equilibrium and thermodynamic analysis of dye adsorption, the effects of pH, temperature, adsorbent dosage, and initial dye concentration on adsorption capacity were investigated.
Next, the catalytic valorisation of plastic waste was investigated using CrPC. The catalytic pyrolysis technique was used to recycle the plastic using polypropylene as a model plastic. Two catalysts, namely, CrPC and calcined clay, were utilized for this purpose. The effects of pyrolysis temperature and catalyst-to-feed ratio on yields of gas, liquid, char, products were investigated. Through optimization, it could be shown that over 92% of the polypropylene could be converted into its starting raw material, naphtha. Thus, the technique led to a circular process where plastic waste could be recycled.
Key Words: Natural clay, binder, removal of dyes, catalytic pyrolysis, plastic recycling, circular process, sustainable materials, and processes
References:
1. Hari D., Kannan A., G. Reddy, Sustainable and rapid pillared clay synthesis with applications in removal of anionic and cationic dyes Microporous and Mesoporous Materials, February 2023. https://doi.org/10.1016/j.micromeso.2023.112488
2. Hari D., Kannan A, Sustainable Synthesis of Green Adsorbent Pellets with Optimal Attributes of Capacity, Strength, and Cost from Powdered Activated Carbon, Powder Technology, June 2023. https://doi.org/10.1016/j.powtec.2023.118763
3. Hari D., Kannan, A.: Synthesis of Pillared Clay Adsorbents and Their Applications in Treatment of Dye Containing Wastewater, Polymer Technology in Dye-containing Wastewater, Springer 2022. https://doi.org/10.1007/978-981-19-1516-1_6