Cationic dyes adsorption by Na-Montmorillonite Nano Clay: Experimental study combined with a theoretical investigation using DFT-based descriptors and molecular dynamics simulations

Mechanical and compressibility characteristics of a soft clay stabilized by slag-based mixtures and geopolymers

A laboratory study was undertaken to evaluate and compare the stabilization effectiveness of different percentages (0, 2.5, 5, 7.5, 10%) of quick and hydrated lime when applied separately to locally available lateritic soil, a major soil group in the tropical and sub tropical regions. Performance evaluation experiments included: Atterberg limits, compaction, unconfined compression tests, California bearing ratio (CBR), swelling potential using CBR instrument and hydraulic conductivity. The soil mixtures used for unconfined compressive strength (UCS), CBR, swelling potential and hydraulic conductivity tests were compacted at optimum moisture content using the British standard light compactive effort and cured for 28 days. It was found that the quicklime caused the soil to have lower plasticity while hydrated lime yielded higher dry unit weight. Also, higher UCS especially at higher dosages (7.5 and 10%) was produced when soil sample was treated with quicklime. Similarly, the CBR values for quicklime sample clearly indicate that quicklime-stabilized soil have superior load bearing capacity. Finally, quicklime treated specimens reached slightly lower swelling values than the hydrated lime while no appreciable distinction in hydraulic conductivity values of specimens treated with the two types of lime was observed. From the foregoing results, quicklime is adjudged to have exhibited somewhat superior engineering properties and therefore creates a more effective stabilization alternative for the soil.

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Use of quick and hydrated lime in stabilization of lateritic soil: comparative analysis of laboratory data

In this study, the effect of ground granulated blast furnace slag (GGBFS) and recycled construction waste (CW) on bentonite clay stabilisation were investigated. The unconfined compressive strength (UCS) of specimens was evaluated with different combinations of GGBFS and CW over various curing periods. A series of micro analysis tests consisting of scanning electron microscope, energy dispersive spectrometer and X-ray diffraction were also conducted to determine the microstructural arrangement and mineralogical effect of the stabilisation treatment. The UCS results showed an increment in strength after introduction of GGBFS and CW and the longer curing period produced more pronounced results. The optimum additive ratio was calculated as 5 % of slag and 20 % of construction waste under all curing conditions. The micro analytical results also indicated formation of structural bonds between admixtures and bentonite in stabilised specimens, as slag crystals and bentonite particles were observed to occupy the cavities and vesicles on the construction waste grains. However, the experimental data shows that the strength improvement is not significant with the addition of only construction waste.

Experimental Evaluation of Construction Waste and Ground Granulated Blast Furnace Slag as Alternative Soil Stabilisers

Water, being the crucial feature of our planet, the contamination of which is a grave matter of concern globally. Elimination of tenacious pollutants from the aquatic phase is indispensable for the sustainability of this planet. Adsorptive sequestration of pollutants is a highly cherished way owing to its design simplicity, economic feasibility and, higher efficacy than various reported treatment methods. Amidst the ample range of adsorbents employed for an environmental cause, clay-hydrogel nanocomposites (CHN) are emerging as an enticing materials platform for wastewater treatment owing to their high sorption capacity, affinity, environmental viability, tailorable physiochemical characteristics, and better reusability. The presence of various functional groups in the polymer chain –OH, –COOH, –NH2 along with the adsorptive potential of clays validate them as a hot spot sorbent. This review initially summarizes the synthetic methodologies of various clay-hydrogel nanocomposites and then their utilization in the seizure of pollutants from the aquatic realm. The removal mechanism which governs the uptake of pollutant on the clay-hydrogel nanocomposites has been thoroughly reviewed which illustrated that electrostatic interaction, hydrogen bonding, and complexation are the prime ways to sequester dyes and metals on CHN. Discussion on isotherm and kinetic models along with thermodynamic study is also provided. Regeneration efficiency of CHN was also discussed demonstrating HCl to be potent desorbing agent than various acids and organic solvents. Finally, the future perspective for the advancement of CHN in the direction of modern technological facets is also detailed out.

Clay-hydrogel nanocomposites for adsorptive amputation of environmental contaminants from aqueous phase: A review

The stabilization of problematic fine-grained soils using lime as an admixture is a widely accepted practice, owing to its simplicity and cost-effectiveness. The optimal quantity of lime required for soil stabilization primarily depends upon the reactive nature of soil as well as the degree of improvement desired. The term ‘optimum lime content’ (OLC) defines the amount of lime required for satisfying the immediate/short-term soil–lime interaction, and still providing sufficient amount of free calcium and high residual pH necessary to initiate long-term pozzolanic reaction. Previous researchers proposed various empirical correlations and experimental methodologies for determining OLC, in terms of clay-size fraction and plasticity characteristics of virgin soil. However, the limiting lime content obtained using various conventional methods does not account for the most influencing inherent clay mineralogy of the soil; and hence, the results of these methodologies are observed to be quite disagreeing with each other. In view of these discrepancies, the present study attempts to validate the existing conventional methodologies for OLC determination at an elementary level, by comprehending the fundamental chemistry following soil–lime interactions. Based on the theoretical and experimental observations, it is quite evident that the accuracy of conventional tests is limited by combined influence of chemical and mineralogical properties of soils. Hence, it is proposed to develop a precise methodology to ascertain the required optimal lime dosage based on scientific criteria, by incorporating the influence of soil properties such as clay mineralogy, specific surface area, soil pH, cation exchange capacity, soil acidity, base saturation capacity, and buffer capacity.

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A Critical Appraisal of the Role of Clay Mineralogy in Lime Stabilization

Calcium adsorption on clays: Effects of mineralogy, pore fluid chemistry and temperature

The recent research infers that the detailed characterization of lime-treated soils using analytical techniques enables better understanding of the complex soil–lime interaction mechanisms as well as the pivotal factors influencing the efficacy of lime treatment. In view of this, the present study focuses on evaluating the effects of lime treatment on the strength properties of sodium bentonite clay in terms of the variations in thermal characteristics derived by employing analytical thermogravimetric analysis. This technique is effectively used to monitor the consumption of free lime and evolution of new cementitious hydration products (viz., calcium silicate hydrate and calcium aluminate hydrate), as well as detrimental lime carbonation phenomenon occurring in the sodium bentonite-lime composite during short-term curing. Based on the comparative evaluation of untreated and lime-treated sodium bentonite, variations in the weight loss corresponding to thermal decomposition of different chemical phases are estimated. The additional inferences from X-ray diffraction and Fourier transform infrared spectroscopy analyses substantiated the interpretations of thermogravimetric results regarding the lime stabilization mechanisms and consequent strength evolution in sodium bentonite-lime composites. Thus, the present study demonstrates that the comprehensive analysis of thermogravimetric results enables reliable interpretation of the soil–lime interaction mechanisms and the evolution of strength during curing.

Characterization of Lime-Treated Bentonite Using Thermogravimetric Analysis for Assessing its Short-Term Strength Behaviour

The quantification of the kinetics of short-term clay–lime interactions is a key step for optimizing the parameters during lime stabilization of fine-grained soils, and also for predicting the long-term performance of lime treated soil matrix. The existing scientific literatures often believed that monitoring of consistency limits as well as compaction characteristics of lime treated soils yield significant amount of information regarding their physico-mechanical behaviour. However, apparently limited extent of works has been carried out to assess the role of clay mineralogy and pore fluid chemistry on inherent variations in plasticity and compaction characteristics. Further, no definite single conclusion could be drawn from the previous studies conducted to comprehend the plausible mechanisms of stabilization occurring in the lime treated soils during short-term and long-term interaction periods.In order to enhance the current understanding, this study primarily focused on the critical evaluation of plasticity properties and compaction characteristics variations of lime treated soils with respect to change in pore fluid chemistry (such as pH and concentration of lime). The study employed soils with quite diverse physico-chemical and mineralogical compositions so as to highlight the role played by the clay mineralogy in governing the extent of short-term improvement that can be mobilized by lime treatment. Based on the significant observations gathered from experimental works, attempts have been made to elucidate the possible short-term mechanisms of lime stabilization which also contribute to long-term strength and durability of lime treated soil.

Chinchu Cherian

Papers

A Critical Appraisal of the Role of Clay Mineralogy in Lime Stabilization

Calcium adsorption on clays: Effects of mineralogy, pore fluid chemistry and temperature

Characterization of Lime-Treated Bentonite Using Thermogravimetric Analysis for Assessing its Short-Term Strength Behaviour

Re-Appraisal of the Physico-Mechanical Stability of Lime Treated Soils

Evaluating the Performance of Wood Fly Ash and Polymer as an Environmentally Friendly Remediation Technique for Wildfire Impacted Forest Soils