Adsorption of dyestuff by nano copper oxide coated alkali metakaoline geopolymer in monolith and powder forms: Kinetics, isotherms and microstructural analysis

An efficient eco-friendly adsorbent material based on waste copper slag-biomass ash geopolymer: dye sorption capacity and sustainable properties

The primary intent of the research is to comprehensively assess the environmental benefits and cost dynamics associated with the adsorption process of CS-RHA (Copper Slag and Rice Husk Ash) to produce a novel geopolymer adsorbent material for application in wastewater treatment. The geopolymer forms a polyiron sialate network under alkali activation by dissolving fayalite, and aluminium silicate to ferro-ferri silicate hydrate gel. The mechanical strength, leaching characteristics, and microstructure of the geopolymer were determined using XRD and FTIR, and magnetic properties by VSM as well surface properties were derived from BET surface area and zeta potential. Recognizing the critical role of sodium iron silicate hydrate (NFS) in the sorption of methylene blue (MB) dyestuff, batch experiments were carried out using different adsorbents. The results indicated that the dye removal efficiency increased from 60% in control samples (FS) to 98% for the blend (FS1) under different pH values. The data was found to fit with the nonlinear form of Freundlich isotherm and follow pseudo-second-order kinetics. The active adsorption sites were deduced as -O-Fe-O-Si-O-Na and Si-OH groups. The addition of RHA increases the adsorption capacity of the geopolymer in a short time through chemical adsorption. The significant negative surface charge promotes MB adsorption via improved electrostatic attraction. The spent adsorbents were recovered through magnetic separation with a retrieval rate of 80-85% and active sites were rejuvenated by calcination. Consequently, waste copper slag emerges as a promising adsorbent with minimum potential ecological risk and high effective recycling capacity.

How to apply terpenoid-based deep eutectic solvents for removal of antibiotics and dyes from water: Theoretical prediction, experimental validation and quantum chemical evaluation

This study proposed a theoretical prediction method and mechanism investigation for the extraction of antibiotics and dyes from aqueous media using terpenoid-based deep eutectic solvents (DESs). Firstly, Conductor-like Screening Model for Real Solvents (COSMO-RS) approach was applied to predict selectivity, capacity and performance index in the extraction of 15 target compounds including antibiotics (tetracyclines, sulfonamides, quinolones, β-lactams) and dyes by 26 terpenoid-based DESs, and thymol-benzyl alcohol shows promising theoretical selectivity and extraction efficiency for the target compounds. Moreover, the structures of both hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) have an impact on the predicted extraction performance, which can be improved by tailoring those candidates with higher polarity, smaller molecular volume, shorter alkyl chain length and the presence of aromatic ring structures, etc. According to the predicted molecular interactions revealed by σ-profile and σ-potential, the DESs with HBD ability can promote the separation process. Furthermore, reliability of proposed prediction method was confirmed by experimental verification, indicating that the trends of theoretical extraction performance index were similar with the experimental results by using actual samples. At last, the extraction mechanism was evaluated by quantum chemical calculations based on visual presentations, thermodynamic calculations and topological properties; and the target compounds showed favorable energies of solvation to transfer from aqueous phase to DESs phase. The proposed method has been proved with potential to provide the efficient strategies and guidance for more applications (e.g., microextraction, solid phase extraction, adsorption) with similar molecular interactions of green solvents in environmental research.