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Silica-based aerogel composite was prepared adopting sol–gel technique combined with atmospheric drying method utilizing waste environmentally hazardous iron tailings. High-temperature alkali fusion was applied to extract the Si, Al and Fe in the tailings so as to maximize recovery of valuable elements. The SiO2-Al2O3 (SA) and SiO2-Al2O3-Fe2O3 (SAF) aerogel composites were subjected to assess its adsorption capacity for macromolecules, utilizing methylene blue (MB) as the adsorbate. The specific surface areas of the SA and SAF aerogel were estimated to be 922.03 m2/g and 683.84 m2/g. The equilibrium adsorption capacity for MB was estimated to be 318.47 mg/g and 334.44 mg/g, respectively. Although the specific surface area of SAF was lower than SA, it offered higher MB adsorption capacity which could be attributed to the presence of iron oxide. The results promised utilization of iron tailing generated aerogel composite as a potential adsorbent for separation of high molecular weight compounds.

The potential of utilizing shiitake mushroom as feed stock for the preparation of activated carbon by chemical activation method with $$\text {K}_{2}\text {CO}_{3}$$ was explored. The prepared materials were characterized by thermogravimetric analysis, $$\text {N}_{2}$$ adsorption–desorption analysis, scanning electron microscope, Fourier transform infrared spectrometer, X-ray diffraction and Raman spectra. The activation mechanisms were proposed with the aid of thermogravimetric analysis. X-ray diffraction and Raman analysis indicated that the activated carbon was amorphous macroscopically. The influences of activation temperature, mass ratio of $$\text {K}_{2}\text {CO}_{3}$$ /shiitake mushroom, activation duration, heating rate and material mixed mode on the yield, porosity and surface morphology of the activated carbon were investigated in detail. The synthesized activated carbons was predominantly microporous having a specific surface area of 2330 m $$^{2}$$ /g, and the optimal process conditions were activation temperature of 800 $$^{\circ }$$ C, mass ratio of $$\text {K}_{2}\text {CO}_{3}$$ /shiitake mushroom of 1.5, activation duration of 180 min, heating rate of 5 $$^{\circ }$$ C/min and mixed mode of impregnation. Addition to high surface area, it also exhibited a high iodine number adsorption capacity of 1432 mg/g and methylene blue adsorption capacity of 872 mg/g, which are far higher than the adsorption capacities reported in the open literature. These results demonstrate that the synthesized activated carbon could be utilized for variety of industrial applications.

The feasibility of preparing glass ceramic from chambersite gravity tailings was explored. The crystallization parameters and state of glass ceramic were analyzed by Johnson–Mehl–Avrami and Augis–Bennett equations. The effects of sintering temperature and crystallization duration on bending strength and water absorption of glass ceramic were investigated, while the phase composition, crystal structure, lattice constants and surface topography were characterized. The results indicate the crystallization behavior of chambersite tailings glass ceramic is mainly body crystallization with clinopyroxene as a primary crystalline phase, the activation energy for crystallization (E) is 315.27 kJ/mol, the kinetics parameter for crystallization (k) is $$7.98\times 10^{14}$$ , and the main phase lattice constants of clinopyroxene were $$a=0.97392$$ nm, $$b=0.88521$$ nm, $$c=0.52748$$ nm, $$\beta =107.062{^{\circ }}$$ . At sintering temperature of 890 $$^{\circ }$$ C, pyroxene crystal with tetragonal column structure is formed, the diameter of the crystal is about 0.05–0.5 $$\upmu $$ m, while the crystallinity is more than 75%; the bending strength of the glass ceramic increases with the decrease in material particle size; at the $$\hbox {D}_{90}$$ of 5.71 $$\upmu $$ m and crystallization duration of 150 min, the bending strength of glass ceramic reaches the maximum of 128.3 MPa and the water absorption is between 0.06 and 0.02%.

The removal of $$\hbox {H}_{2}\hbox {S}$$ from copper smelting contaminated acid using sodium hydroxide (NaOH) as absorbent was investigated in a RPB reactor. The influences of operating parameters were assessed on the removal efficiency of $$\hbox {H}_{2}\hbox {S}$$ (E) and overall volumetric gas side mass transfer coefficient ( $$K_{\mathrm{G}}a$$ ). The results illustrate that E and $$K_{\mathrm{G}}a$$ increased with increase in high gravity factor, flow rate and concentration of sodium hydroxide while decreased with increase in mass concentration of $$\hbox {H}_{2}\hbox {S}$$ in feed gas. With increase in $$\hbox {H}_{2}\hbox {S}$$ gas flow rate, E was found to decrease while $$K_{\mathrm{G}}a$$ was found to increase. The increase in the temperature of absorption did not show any significant effect on E and $$K_{\mathrm{G}}a$$ . The $$K_{\mathrm{G}}a$$ of the rotating packed bed reactor was about 30 times higher than the conventional packed bed at similar gas liquid throughputs. The superior performance of RBP certainly demands further investigation, process development, scale-up for economical commercial adoption.

Process optimization of vanadium nitride synthesis from vanadium pentoxide was attempted utilizing microwave carbothermal nitridation at atmospheric pressure using response surface methodology. The process variables that have significant influence on the quality of vanadium nitride such as the reaction temperature, reaction time and carbon addition ratio were investigated. The quadratic models were developed to evaluate the variables and optimize the process conditions, while the analysis of variance was utilized to identify the significant model parameters. The optimum conditions were identified to be a reaction temperature of \({1400^{\circ}{\rm C}}\), reaction time of 240 min and carbon addition ratio of 0.29; the nitride and vanadium content in the vanadium nitride products was found to be 15.83 and 80.99 %, respectively. Experiments were repeated, and the results authenticated the optimized process conditions successfully.

This paper attempts to capture the difference between the ultrasound augmented and conventional sulphuric acid leaching of zinc from zinc residue, having a Zn content of 12.31 %, along with other metallic compounds such as Fe, Pb and SiO2. The leaching temperature, sulphuric acid concentration, particle size, Liquid/solid ratio and the ultrasound power have been chosen as parameters for investigation. The shrinking core model is utilized for analyzing the rate controlling step in the leaching process. Only a maximum of 67 % of zinc could be leached using conventional process, while 80 % could be leached with the ultrasound augmentation. For both the processes the rate controlling step is identified to be the diffusion through the product layer. The reaction order with respect to the sulphuric acid concentration is found to be 1.33 and 0.94, while the activation energy being are 13.07 and 6.57 kJ/mol, for the conventional and ultrasound-augmented leaching process, respectively. The raw as well as the leached residue are characterized using XRD and SEM/EDS analyses.