Enhancing the properties of geopolymer concrete using nano-silica and microstructure assessment: a sustainable approach.

Nowadays low calcium fly ash-based geopolymer concrete can be replaced with cement-based concrete to avoid the adverse effect of manufacturing cement on the environment. Utilization of geopolymer concrete instead of traditional concrete using low calcium fly ash and nano silica reduces a significant amount of CO-2 emission towards the atmosphere. However, the performance of geopolymer concrete is less than that of Portland cement concrete. To improve the performance of geopolymer concrete nano silica was used in the present study. In this work, geopolymer concrete was made utilizing fly ash, ground granular blast furnace slag (GGBS), and sugarcane bagasse ash. In the first instance, binary combinations i.e. fly ash and GGBS were employed as cementitious materials for the production of geopolymer concrete. In the second instance, a ternary mixture of pozzolanic material was prepared by taking 25% GGBS, 65% Fly ash, and 10% bagasse ash. In the third instance, varying percentages of nanoparticles were used for the above ternary mixture. The mechanical and durability properties of the geopolymer composite that was made earlier were tested. The compressive strength and split tensile strength of geopolymer composites were assessed for mechanical properties and a rapid chloride permeability test, water absorption test, and acid attack test were done to know about the porosity of concrete. Results showed that, with a dose of 4% nanoparticles, the durability and strength properties of the concrete had improved the most. The GCBA-N4 mixture had the highest split tensile and compressive strength was measured to be 2.91 MPa and 41.33 MPa and the rapid chloride permeability test, water absorption rate, and percentage of mass loss due to sulfate attack were found as a minimum for GCBA-N4 specimen.

Adsorption isotherm, kinetics and response surface methodology optimization of cadmium (Cd) removal from aqueous solution by chitosan biopolymers from cephalopod waste.

The present investigation was aimed to explore the cadmium removal efficiency, mechanism and characterization of Chitosan biopolymers from cephalopods waste. The extracted chitosan has showed good yield of 32% and with high minerals, ash and moisture content. In the Fourier-transform infrared spectroscopy (FT-IR) analysis multiple active functional groups of Amine, Amine, Hydroxyl were found between 612 and 3424 cm-1 and the sugar signals such as N-acetyl glucosamine (GlcNAc) and H-1 [GlcN (H-1D), GlcNAc (H-1A)] were identified in Chitosan by 1H Nuclear Magnetic Resonance (NMR). The Crystalline, rough surface, micropores characters were observed in Chitosan surface by Scanning Electron Microscope (SEM) analysis and the pores played a key role in adsorption process. The Cd ions removal was performed by batch experiment and the results were revealed that the pH, temperature, time and dosage highly influenced the process and the optimum condition was discovered through RSM for pH 7, temperature 42.5 °C, time 220 min and dosage of sorbent 1 g/L respectively. The kinetics models of the Cd removal were carried out and the results revealed that the Pseudo-second order is more suitable and fit for removal than Pseudo-first order model. Chitosan surface characters and functional groups played a big role in adsorption process and Chitosan can be alternative eco-friendly, low cost and highly efficient sorbent for heavy metal removal in effluent treatment plants.

Effective removal of fluoride ions from aqueous solution by marine microalgae as natural biosorbent.

In this study, the phytoremediation technology from marine source Dunaliella salina was chosen to eliminate fluoride ions from aqueous solution by Adsorption isotherm, Kinetics and RSM optimization methods. Marine microalgae were collected, identified and mass cultured then its physical characteristics, functional groups and surface microstructure was examined by FT-IR, NMR, XRD and SEM analysis also the same was performed on post treated bioadsorbent. Fluoride removal was optimized by different conditions through response surface methodology and kinetics modelling also performed. Several active functional groups were noticed in IR spectra and NMR of pre and post treated microalgal biosorbent. Many micropores, crystalline structure, voids were observed in pre-treated and lesser in post treated bioadsorbent, removal process was optimized by temperature, pH, dose and time and its showed high influence of removal process. The fluoride removal process was optimized by response surface methodology, Langmuir Isotherm, Freundlich Isotherm, Temkin isotherm, Pseudo I order, Pseudo II order and Intra particle diffusion and revealed that the F ions removal mechanism clearly. Microalgae are novel, low-cost and effective bio based innovative methods which are sustainable for the bioremediation of fluoride from water bodies and industrial wastewaters.