Volume 23, Issue 6 - Special issue dedicated to the International Symposium “Chemical Engineering – Environment, Sustainability and the Future”

The exponential growth of electronic waste pollution, including outdated electrical equipment, is a significant environmental and health concern. To protect the ecosystem from e-waste contamination, chemical engineering with its prominent processes such as leaching, pyrolysis, etc. can take a leading role in resource recovery, eco-friendly waste management, and sustainable e-waste recycling. This review presents a detailed analysis of e-waste recycling technologies from the chemical engineering perspective. Several smart solutions are discussed for managing and recovering important e-waste components, including semiconductor chips, metals (Pb, Al, Steel, Ni, Ag, Au, Pd), rare-earth minerals, etc. Various metals recovered by electro-winning from cell phones, and integrated circuits, can be used to produce corrosion-resistant appliances, IoT (Internet of Things) devices like sensors, and robotics related to chemical sciences. This paper concentrates on strategies for recovering materials that can be used to make chemical engineering equipment and IoT devices, along with the roadblocks and potential connected with these strategies. This study compares the various e-waste recycling procedures on photoelectronic trash from the last few years. The paper also focuses on green upcycling and effective e-trash management from discarded keyboards into value-added goods like musical tools and innovative artistic sculptures and also from seawater. This paper portrays the pyrometallurgical and valorization of digital rubbish such as printed circuit boards (PCBs), reactors, and transistors for e-waste-based nanorobots. This review also emphasizes the difficulty of managing the growing amounts of e-waste globally and the damaging effects on the environment and human health caused by improper disposal.

The present study conducts a comparative analysis between selective catalytic reduction (SCR) using a Cu-zeolite catalyst and selective non-catalytic reduction (SNCR) for the removal of NO x from industrial waste gas. The primary objective of this investigation is to computationally explore the removal of NO x using NH 3 at various reactor conditions, along with the study of different hydrodynamic aspects. The study revealed the impact of different porosity of the catalyst (in SCR) and the number of baffles (in SNCR) on the reaction and fluid flow profile. Distinct geometries were employed to model each process, incorporating a turbulent model and kinetic parameters with an eddy-dissipation model (EDM) for simulations. Analyzing the effect of the NH 3 /NO ratio on NO conversion efficiency is a crucial component of the study. With diminishing efficiency at higher ratios, the SCR process demonstrated nearly complete NO conversion at a certain NH 3 /NO ratio, and this value changes with the inlet gas temperature. In contrast, SNCR produced less favorable conversion rates than SCR, indicating that the amount of NH 3 supply affects conversion efficiency. At the SCR system’s optimum NH 3 /NO ratio, SNCR achieved an 83 % conversion, and the conversion rate remained relatively constant as the ratio was increased. The results highlight the various possibilities for optimization of the reactor systems in terms of efficiency and economic feasibility.

Critical water crisis due to overpopulation, industrialization and urbanization has resulted to the shortfall of providing safe drinking water to one billion people in the world. This work intends to fabricate modified hydrophobic polyvinylidene fluoride (PVDF) membrane by hydrophilic chitosan extracted from waste fish scales for wastewater treatment. Chitosan was blended with PVDF in N-methyl-2-pyrrolidone solution by solution casting method. Three different concentrations of 1, 3 and 5 wt% of chitosan were taken. The morphological, spectral and thermal analysis of the produced films were elaborately studied. The contact angle decreased with the increase of chitosan content from 82.64° to 60.97°. The tensile strength decreases from 1.11 to 0.38 MPa and Young’s modulus decreased from 12.08 to 7.4 MPa with increase in chitosan content in the film from 1 to 3 %. The performance of microparticle embedded membrane was compared with the pristine PVDF membrane, and it was affirmed that the microsized-chitosan embedded PVDF membrane manifests a broad promising application perspective towards wastewater treatment owing to its excellent water flux (76 L m −2  h −1 ) as well as antibacterial properties.

The sodium magnesium contains double perovskite structure compound i.e. NaSrBi 1- x Eu x WO 6 is synthesized by using citrate – gel method. This double perovskite structure compound is prepared at different concentrations i.e. ( x  = 0.0–0.24) at different temperatures 500, 600, 700 °C for 5 h. Further, the prepared samples are characterized through different tools like XRD (X-ray diffractro meter), UV Visible Diffuse Reflectance Spectra, Photo luminescence spectra, FE SEM and CIE Software and the prepared sample shows different structures in various concentrations by using X-ray diffractrometer. Similarly, lattice parameters, peak positions are explained for all various concentrated samples at 700 °C sintered temperature for 5 h. However, the samples which are sintered at 700 °C for 5 h are excited at different wavelengths i.e. 395, 465, 540 nm, the corresponding emission intensities are also recorded. All the concentrated samples exhibits towards high intensity peaks at 595, 614 nm wavelengths in their emission spectra. The sample x  = 0.12 shows highest red emission intensity out of all concentrations in the emission spectra. 5 D 0 - 7 F 1 & 5 D 0 - 7 F 2 are the major transitions formed in the emission spectra for every concentrated sample. In the same way the structural morphology is identified clearly by using FE SSEM. The CIE color coordinators are calculated and identified as very close to NTSC coordinators of red phosphor. Finally, the color purity is also calculated to analyze the quality of red light for the prepared red phosphor which is used in different W-LEDs applications.

In this study, aqueous solutions of N,N-dimethyldipropylenetriamine (DMDPTA) + N-Methydiethanolamine (MDEA) are evaluated by experimental measurement of mixed solvent density, equilibrium CO 2 solubility and CO 2 absorption enthalpy in the varying range of temperature and composition. CO 2 solubility in the (DMDPTA + MDEA + H 2 O) solutions was measured at three temperatures (303 K, 313 K & 323 K) in the CO 2 partial pressures range of 2–210 kPa with varying DMDPTA mass % ranging from 5 to 15 % keeping total amine concentration at constant 30 mass %. The experimental density data of the formulated solvent were modeled using a Redlich-Keister excess molar volume model with a low average absolute relative deviation (AARD) of 0.011. A modified Kent-Eisenberg model was formulated to fit the experimental vapor-liquid equilibrium (VLE) data of CO 2 solubility in the formulated solvent. The modified Kent-Eisenberg model predictions compared well with the experimental data with AARD of 1.3 %., confirming the robustness of the model in capturing the intricate CO 2 solubility behavior of the examined blended amine solvent over the experimental range. The heat of CO 2 absorption was measured using a reaction calorimeter at 313 K for aqueous (5 % DMDPTA + 25 % MDEA) and (10 % DMDPTA + 20 % MDEA) solvents which also showed lower value of absorption enthalpy compared to the benchmark solvents like Monoethanolamine (MEA).