Efficient adsorption of hexavalent chromium ions onto novel ferrochrome slag/polyaniline nanocomposite: ANN modeling, isotherms, kinetics, and thermodynamic studies.

The current research is concerned with the adsorption behavior of chromium (IV) ions in an aqueous solution using a novel ferrochrome slag/polyaniline nanocomposite (FeCr-PANI) adsorbent. The effect of process parameters such as temperature, pH solution, initial Cr (VI) ions concentration, adsorbent dosage, and contact time on the adsorption process is experimentally investigated in this study. Furthermore, we have trained a multilayer artificial neural network (ANN) using the experimental data of various process parameters to successfully predict the adsorption behavior of chromium (IV) ions onto the FeCr-PANI adsorbent. The ANN model was trained using the Lavenberg-Marquardt algorithm and ten neurons in the hidden layer and was able to estimate the % removal efficiency of chromium (IV) under the influence of different process parameters (R2 = 0.991). Initial solution pH was observed to have a significant influence on the % removal efficiency. The % removal efficiency was found to be high at 97.10% for the solution with pH 3 but decreased to 64.40% for the solution with pH 11. Cr (VI) % removal efficiency was observed to increase with an increase in solution temperature, adsorbent dosage, and contact time. However, the % removal efficiency was found to decrease from 96.9 to 54.8% with increasing the initial dye concentration from 100 to 400 ppm. Furthermore, the adsorption capacity increased from 9.69 to 21.93 mg/g with an increase in the initial concentration from 100 to 400 ppm, as expected. The Langmuir isotherm model exhibited the best fit with the experimental data (R2 = 0.9977). The maximum adsorption capacity was found to be 22.523 mg g-1 at 298 K. The experimental data fitted well with the pseudo-second-order kinetic model.

Reuse of lead glass sludge in the fabrication of thermally insulating foamed glass with outstanding properties and high Pb-stabilization.

This study represents the sustainable/safe consumption of lead glass sludge (LGS) in the fabrication of thermally insulating foamed glass via sintering (750-950º C) and chlorination processes. The impact of selected additives including calcium chloride (CaCl2) and sodium hydroxide (NaOH) on the foaming efficiency and Pb-stabilization has been deeply investigated. LGS is mainly lead silicate material with considerable content of calcium carbonate, which acts as foaming agent during sintering process. The newly developed foamed-materials exhibited thermal conductivity of 0.054-0.136 W/m.K, density of 0.23-1.10 g/cm3, porosity of 63.3-92.6%, and compressive strength of 0.10-2.69 MPa. X-ray diffraction proved that the immobilization mechanism was attributed to the transformation of free Pb within LGS into insoluble ganomalite Pb9Ca5MnSi9O33 phase. Adding NaOH enhanced the foaming process accompanied by a significant reduction in Pb-leaching. Incorporating CaCl2 has resulted in a retardation in Pb-leaching, which associated with Pb-stabilization and Pb-vaporization. In an attempt to reduce CO2-emission, the potential use of alkali-rich-wastewater (AW) as eco-friendly alkali source in lieu of NaOH was studied. Regardless of the variation in Pb-concentrations in leachates, all samples recorded Pb-concentrations lower than the safe limit (≤ 5 mg/l), achieving Pb-immobilization of 95.98-99.87%. The significantly reduced thermal conductivity and enhanced Pb-immobilization efficiency along with the reasonable compressive strength summarize the major innovation presented in this study.