The effect of modification of Montmorillonite clay (MMT) and the development of its hybrid with reduced graphene oxide was studied for CO₂ adsorption at low pressure. Novel polyphosphoric acid modified montmorillonite (PMMT) clay was synthesized by cation exchange reaction to improve the surface area and thereby improving the carbon dioxide adsorption capacity. The MMT clay, polyphosphoric acid modified clay (PMMT), and amino modified clay (AMMT) were hybridized with reduced graphene oxide (rGO) by in-situ hydrothermal reduction of graphite oxide for CO₂ adsorption studies. The hybrids were characterized using X-ray diffraction (XRD) analysis, Fourier Transform Infrared (FTIR) analysis, Field Emission Scanning Electron Microscopic (FESEM) and Transmission Electron Microscopic (TEM) analyses. The Brunauer–Emmett–Teller (BET) surface area analysis confirmed a surface area of 50.7709 m²/g for PMMT/rGO hybrid, which was higher than that of MMT/rGO and AMMT/rGO hybrids. In general, all hybrids were active in CO₂ adsorption at comparatively low pressure [ranging from 0 to 900 mmHg]. PMMT/rGO hybrid showed highest CO₂ adsorption of 0.49 mmol/g and this was 42% more in CO₂ adsorption when compared to other materials studied in this paper. The low pressure CO2 adsorption values obtained for PMMT/rGO hybrid was substantially good when compared to the literature results and this shows the importance of clay based materials for the development of efficient adsorbent for CO₂.

The removal of organic dyes from the aquatic system using modified Montmorillonite clay (MMT), one of the low cost adsorbent, was studied in this paper. Polyphosphoric acid (PPA) modified MMT (PMMT) with better surface area was used for adsorbing cationic dyes such as methylene blue(MB), rhodamine B (RB) and anionic dye Rose Bengal. The adsorption capacity of the PMMT clay for MB, RB and Rose Bengal dyes were 293.9 mg g⁻¹, 244.77 mg g⁻¹ and 296.13 mg g⁻¹ respectively and all follows pseudo second order kinetics with Langmuir adsorption isotherm model. For better practical application polyvinyl alchohol (PVA) thin film composite with PMMT as filler was prepared and the adsorption studies were conducted. PVA composite film with 0.5 w/v% PMMT filler was found to be a good adsorbent for the cationic dye than anionic dyes and adsorbs 99% of MB dye from 30 mgL⁻¹ dye solution. The composite film showed pseudo second order kinetics and better fit with the Langmuir model and the mono layer adsorption on the clay surface can be explained by electrostatic interaction between adsorbent and adsorbate. The introduction of the PMMT clay in the PVA matrix increases the thermal stability of neat PVA. Tensile strength of the composite was showing a gradual increase with the amount of PMMT filler and at 0.4% addition of PMMT in PVA, the tensile strength was increased up to 39% when compared to PVA film.

Graphene-based polymer aerogels are one of the important solutions for the adsorption of CO₂. In the present study, we have developed an economic, uncarbonized polyvinyl alcohol (PVA) based aerogel through the freeze-drying method using modifed clay- reduced graphene oxide (rGO) hybrid as fller. The CO₂ capture efciency of PVA-modifed clay/rGO aerogel containing the hybrid fller in three diferent concentrations such as 0.1 w/v%, 0.5 w/v% and 1 w/v% at 25⁰C and comparatively low pressure ranging from 0 to 900 mmHg was studied. The polyphosphoric acid (PPA) modified montmorillonite (PMMT)/rGO hybrid was synthesized by the hydrothermal method by varying the ratio of the individual components in 2:1 and 1:2 ratios and compared with a 1:1 ratio hybrid. The powdered hybrids were characterized and analyzed for CO₂ adsorption analysis. All the powdered hybrids were showing good CO2 gas adsorption efciency and the efciency was increased with an increase in rGO content and hybrid with 1:2 ratio showed a CO₂ adsorption efciency of 0.53 mmol g−1. PVA aerogel was synthesized using 1:1 and 1:2 PMMT/rGO hybrids and CO₂ adsorption capacity were analyzed. PVAPMMT/rGO aerogel of 1:2 ratio with 0.5 w/v% showed only 0.176 mmol g−1 whereas PVA-PMMT/rGO aerogel of 1:1 ratio with 0.5 w/v% showed an excellent CO₂ adsorption capacity of 0.238 mmol g−1 at 900 mmHg at 25⁰C temperature and it is signifcantly high when compared with the literature results. The developed PVA-PMMT/rGO hybrid aerogel is an excellent material for CO₂ adsorption and it can be directly used for reducing the CO₂ level in the atmosphere.