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We present here a tribute to Maarib Bazzaz (1940-2020), formerly Maarib Darwish Lutfi Bakri, who was an innovative and a highly inquisitive plant physiologist of her time. Her research achievements include exploitation of a highly productive mutant of maize (ON8147), of differences between mesophyll and bundle sheath chloroplasts of maize, and of chlorophyll (Chl) biosynthesis. Above all, she provided convincing scientific proof that, in addition to the usual monovinyl Chl a and monovinyl Chl b, divinyl Chl a (4-vinyl-4-desethyl-Chl a) and divinyl Chl b (4-vinyl-4-desethyl-Chl b) exist in plants. We also include here reminiscences by some of her contemporaries. Particularly noteworthy is how effortlessly Maarib pursued her deep interest in science while raising two wonderful children. She was always curious about life’s mysteries and determined to search for answers in a thorough and logical manner. Above all and at all times, she was very kind to others.

The widespread generation of, ever increasing volumes of and the sustainable management of solid wastes are global issues of great concern. Due to wide variations in composition and associated complexities, significant efforts are required for their collection, processing and environmentally safe disposal in a cost effective manner. An overview of solid wastes is presented in this article with a specific focus on municipal solid wastes and industrial waste from the iron/steelmaking and aluminium industries. Key waste issues such as its sources, compositions, volumes, the factors affecting waste generation and waste processing are first discussed, followed by a further discussion regarding recycling, resource recovery, disposal and the associated environmental impacts. In a special case study, waste generation and management in Chile is presented in greater detail. Detailed information is provided on government initiatives and legislation for integrated solid waste management and its movement towards a circular economy. Measures include regulations on waste management framework which concerns the transboundary movements of hazardous wastes, persistent organic pollutants, the closure of mining activities and installations and restrictions on plastics disposal. With Chile being world’s largest producer of copper, significant efforts for mining waste management, its infrastructure and procedures are being put in place to reduce the environmental impact of the mining sector and its associated waste generation.

Thermo-electrochemical cells (also known as thermocells, TECs) represent a promising technology for harvesting and exploiting low-grade waste heat (

The Special Issue on ‘Environmental Sustainability of Current Waste Management Practices’ was a part of the section ‘Environmental Sustainability and Applications’ of the journal ‘Sustainability’ [...]

High temperature pyrolysis investigations were carried out on waste printed circuit boards (PCBs) in the temperature range 800-1000°C under inert conditions, with an aim to determine optimal operating conditions for the recovery of copper. Pyrolysis residues were characterized using ICP-OES analysis, SEM/EDS and XRD investigations. Copper foils were successfully recovered after pyrolysis at 800°C for 10-20 min; the levels of Pb and Sn present were found to be quite low and these were generally present near the foil edges. The relative proportions of Pb and Sn became progressively higher at longer heating times due to enhanced diffusion of these molten metals in solid copper. While a similar behaviour was observed at 900°C, the pyrolysis at 1000°C resulted in copper forming Cu-Sn-Pb alloys; copper foils could no longer be recovered. Optimal conditions were identified for the direct recovery of copper from waste PCBs with minimal processing. This approach is expected to make significant contributions towards enhancing material recovery, process efficiency and the environmental sustainability of recycling e-waste. Pyrolysis at lower temperatures, short heating times, coupled with reductions in process steps are expected to significantly reduce energy consumption and pollution associated with the handling and processing of waste PCBs.

Managing red mud (RM), a solid waste byproduct of the alumina recovery process, is a serious ecological and environmental issue. With ~150 million tons/year of RM being generated globally, nearly 4.6 billion tons of RM are presently stored in vast waste reserves. RM can be a valuable resource of metals, minor elements, and rare earth elements. The suitability of RM as a low-grade iron resource was assessed in this study. The utilization of RM as a material resource in several commercial, industrial operations was briefly reviewed. Key features of iron recovery techniques, such as magnetic separation, carbothermal reduction, smelting reduction, acid leaching, and hydrothermal techniques were presented. RMs from different parts of the globe including India, China, Greece, Italy, France, and Russia were examined for their iron recovery potential. Data on RM composition, iron recovery, techniques, and yields was presented. The composition range of RMs examined were: Fe2O3: 28.3–63.2 wt.%; Al2O3: 6.9–26.53 wt.%; SiO2: 2.3–22.0 wt.%; Na2O: 0.27–13.44 wt.%; CaO: 0.26–23.8 wt.%; Al2O3/SiO2: 0.3–4.6. Even with a high alumina content and high Al2O3/SiO2 ratios, it was possible to recover iron in all cases, showing the significant potential of RM as a secondary resource of low-grade iron.

Atomic scale understanding of gasification interactions between graphene and CO2 is presently very limited. Extensive reactive force field molecular dynamics simulation studies were carried out on interactions of pristine (Pr) and a monovacancy (MV) graphene with CO2 in the temperature range (4100–5000 K). Gasification kinetics showed a non-linear behaviour with temperature; abnormal thermal behaviour was observed in the intermediate (4200–4400 K) temperature region. Gasification rates were found to be substantially lower in this region due to the formation of relatively stable intermediate structures. Three stages were used to describe the whole reaction process. The first stage involved the formation of defects as 5-membered and 7-membered rings; carbon bonds near these defects tended to elongate or break forming voids or cavities. In the second stage, the carbon chains were broken by interaction with O or CO2, leading to the formation of carbonyl groups and active carbon sites with dangling bonds. In the third stage, a number of CO2 molecules or O atoms were adsorbed on the active carbon sites releasing CO and enhanced gasification. The presence of a monovacancy promoted reaction kinetics only at relatively low temperatures with little influence at higher temperatures.

Atomic level understanding of graphene oxidation behaviour is presently far from complete. During large scale preparation of graphene from graphene oxide (GO), persistent presence of up to 8% residual oxygen is an issue of great concern. Such incomplete reduction is attributed to the presence of highly stable carbonyl and ether groups. Here we present a new approach for limiting the formation and behavior of these functional groups. We report high temperature molecular dynamics simulations on the oxidation process of pristine (Pr) and mono-vacancy (MV) graphene with O2 with specific focus on the initial reaction period. An abnormal thermal behaviour was observed in the onset times of oxidation reactions; significant differences were detected in the nucleation and growth mechanisms and reaction kinetics. Overall reaction kinetics was significantly slower in the thermal region (Pr: 4350–4450 K; MV: 4300–4450 K). By identifying this region experimentally or theoretically, a narrow window of minimal carbonyl group formation and residual oxygen could be created leading to a major breakthrough in the field.

Several industrial wastes including biomass, fly ashes, red mud, mill scales, water treatment residues, have significant concentrations of metal oxides: Fe2O3, Al2O3, TiO2, SiO2 etc. Several efforts have been made towards recovering metals within these wastes. Rather than recovering one metal at a time, we report a novel approach for simultaneously extracting multiple metals from mixed oxides in a single process step. Using three distinct furnaces/heating regimes, the carbothermic reduction of Fe2O3/Al2O3/SiO2 system was investigated at 1450–1700 °C for up to 2 h over a wide composition range. Complete reduction was achieved for both Fe2O3 and SiO2 in all cases leading to the formation of Fe and Fe–Si alloys. The reduction of alumina at moderate temperatures was the key challenge. No alumina reduction was observed during reductions at 1450 °C. A partial reduction of alumina and the formation of Fe–Al alloys was detected in the Al2O3/Fe2O3/C system at 1550 °C. The formation of Fe–Si–Al alloys was also observed in the Fe2O3/SiO2/Al2O3/C system at 1550 °C. Complete reduction of alumina was observed at 1600–1700 °C, even for up to 50 wt% alumina in the system. Optimal operating conditions and reference standards were established for the simultaneous recovery of multiple metals from waste oxides. While conserving natural resources, this novel route will lower the burden on waste storage facilities with significant contributions to the economic and environmental sustainability of industrial waste management.

With specific focus on local structural order, bonding networks, transport properties, and viscosity of the molten ash oxides, we report molecular dynamics simulations on the influence of alkalis (Na2O and K2O) on coke behavior within a blast furnace. Atomistic simulations were carried out on the Al2O3–SiO2–CaO–K2O–Na2O system at 2223 K for a range and relative proportions of Na2O and K2O. Alkalis were seen to have a strong effect on the oxygen bonding networks; the relative proportions of bridging and nonbridging oxygen showed a sharp increase, while significant reductions were observed for tricluster oxygens. Total diffusion coefficients and viscosity showed a highly nonlinear dependence on the relative proportions of two alkalis with large changes observed in the simultaneous presence of alkalis as compared to their individual presence. Our studies have shown that the combined influence of alkalis on the viscosity of molten ash, and associated coke degradation within a blast furnace, is likely to be mu...

Low temperature pyrolysis investigations were carried out on waste lignin, a coproduct of bioethanol production from sugarcane bagasse, in the temperature range 200–800 °C for 15 to 60 min under argon atmosphere. In-depth characterization of resulting chars was carried out using a range of analytical techniques including XRD, HRSEM, EDS, NMR, FTIR, Raman and BET analysis. In addition to good agreement with the published literature, we report the formation of range of multidimensional carbons from waste lignin in the form of nanofibers, micro-ribbons, complex 3D structures and their blends. XRD data showed the evolution of crystalline as well as amorphous structures as a function of temperature. Reaction pathways for structure evolution and associated phase transformations were also identified. The preparation of these novel carbon structural forms from an abundant, waste bioresource could help realize the untapped potential of waste lignin, the exploration of their properties and future applications.

Molecular dynamics (MD) simulations were carried out to determine the influence of alkalis (K2O and Na2O; up to 10%) on the local structural order, bonding networks and fluidity of molten Al2O3-CaO-SiO2 system (2223 K). The behavior of these aluminosilicates, present as mineral matter in cokes/coals, can have a significant influence on the strength and the reactivity of cokes in high temperature regions of a blast furnace. Experimental results on the system indicate an increasing viscosity in the presence of K2O and a decreasing trend for Na2O. Attributing these differences to local distortions and the sizes of K+ and Na+ ions, theoretical investigations on these systems have predicted a reduction in viscosity for both alkalis. Our simulation results have shown that there were only marginal differences in the local structural order and bond lengths in aluminosilicates in the presence of Na2O and K2O; no specific trends were recorded. Significant differences were however observed in the location of these ions in the oxygen bonding networks. While Na+ ions were preferentially located in the bridging/non-bridging oxygen networks, K+ ions tended to be present in various oxygen tri-clusters. With increasing alkali concentrations, the total diffusion coefficients DTotal of Na2O-bearing system were found to increase, while an opposite trend was observed for K2O-bearing systems. Opposite trends observed in total diffusion coefficients of various ions in Na2O-bearing and K2O-bearing systems are expected to result in opposite trends in the viscosity as well. In addition to reproducing experimental trends, these simulations have helped identify key factors influencing the viscosities of aluminosilicates in the presence of alkalis.

The release of potentially toxic elements as airborne fine particulates is a significant environmental risk associated with recycling e-waste. Some of these may redeposit near emission sites or be transported over long distances causing wide-spread pollution. With an aim to identify key factors affecting particulate emissions, we report novel investigations on the adsorptive capture of particulate matter (PM) released during low temperature pyrolysis (600 °C; 15 min) of waste printed circuit boards (PCBs). A significant proportion of the released particulates (5.3 to 37%) were captured by adsorbents located downstream and in close proximity to the emitting source. Data was collected for four different PCBs and three adsorbents: alumina, silica-gel and activated carbon. With sizes ranging from nanoparticles to over 10 µm, adsorbed particulates were present as fines, spheres, oblongs, clusters and larger particles with no specific shape. Of the 24 elements identified initially in waste PCBs, only 14 were detected in released particulates: major PTEs— Zn, Sn, Pb and Cu (up to 400 ppm); minor PTEs— Ni, Mn, Cd, Cr and Ba (up to 10 ppm); trace PTEs— Co, In, Bi, Be and Sb (up to 1 ppm). Key factors influencing the release of PTEs during thermal processing were identified as basic elemental characteristics, densities, melting points, vapor pressures, initial concentrations, local bonding and mechanical strength. These results show that the presence of low melting point/high vapour pressure elements (Zn, Pb, Sn) should be minimised for a significant reduction in PTE emissions during e-waste processing.

An in-depth understanding about the transformation of molten coke ash is significant to uncover the mechanism of coke reaction at high temperature inside a blast furnace. The evolution of local structural order and fluidity of molten coke ash (SiO2-Al2O3-CaO) with the reduction of SiO2 at a fixed Al2O3/CaO ratio was investigated by means of molecular dynamics (MD) simulation. While [SiO4] tetrahedral was the main structural units forming Si-O network, due to the high levels of Al2O3 in coke minerals [AlO4] and a small amount of [AlO5] were the two key structural units forming the Al-O network. The effect of chemical composition on the bond length of Si-O, Al-O and Ca-O is very weak, while the coordination number of Al-O can be slightly influenced by the reduction of SiO2 due to the unstable structure of Al-centered polyhedron compared with [SiO4]. The concentration of bridging oxygen decreases, while that of tricluster oxygen increases with the reduction of SiO2 from the system. Al-centered polyhedrons prefer to be connected by O triclusters, while Si-centered polyhedron favor a link by bridging oxygen. With the decrease of SiO2, more [AlO4] will change from edge-sharing to corner-sharing with similar units. The angular distribution of Si-O-Si exhibits an asymmetric shape with the average value around 151°, while two peaks were observed in the Al-O-Al angular distribution because of the edge-sharing (∼90°) and corner-sharing (∼122°) features in Al-centered polyhedrons. With the reduction of SiO2 from the system, the diffusivity of all atoms increase considerably since the amount of strong Si-O bond decreases. Viscosity estimated from MD simulation decrease with the reduction of SiO2. The good agreement between MD simulated data and experimental data indicates that MD simulation can be adopted to estimate the property change of molten coke ash at high temperature.

The rapid growth of electronic devices, their subsequent obsolescence and disposal has resulted in electronic waste (e-waste) being one of the fastest increasing waste streams worldwide. The main component of e-waste is printed circuit boards (PCBs), which contain substantial quantities of precious metals in concentrations significantly higher than those typically found in corresponding ores. The high value and limited reserves of minerals containing these metals makes urban mining of precious metals very attractive. This article is focused on the concentration and recovery of precious metals during pyro-metallurgical recycling of waste PCBs. High temperature pyrolysis was carried out for ten minutes in a horizontal tube furnace in the temperature range 800–1350 °C under Argon gas flowing at 1 L/min. These temperatures were chosen to lie below and above the melting point (1084.87 °C) of copper, the main metal in PCBs, to study the influence of its physical state on the recovery of precious metals. The heat treatment of waste PCBs resulted in two different types of solid products, namely a carbonaceous non-metallic fraction (NMFs) and metallic products, composed of copper rich foils and/or droplets and tin–lead rich droplets and some wires. Significant proportions of Ag, Au, Pd and Pt were found concentrated within two types of metallic phases, with very limited quantities retained by the NMFs. This process was successful in concentrating several precious metals such as Ag, Au, Pd and Pt in a small volume fraction, and reduced volumes for further processing/refinement by up to 75%. The amounts of secondary wastes produced were also minimised to a great extent. The generation of precious metals rich metallic phases demonstrates high temperature pyrolysis as a viable approach towards the recovery of precious metals from e-waste.

High temperature interactions of alumina–carbon refractories with molten iron were investigated at 1,823 K in argon atmosphere. These studies were specifically focussed on the decomposition of alumina in the simultaneous presence of carbon and iron, and associated refractory degradation. Refractory mixtures were prepared by blending 90 wt% alumina with 10 wt% synthetic graphite; 5–15 wt% iron powder was then mixed with the refractory mixture. Using phenol formaldehyde as a binder, pellets were prepared from various blends; these were heat treated at 1,823 K for 30 min in Ar atmosphere. The presence of molten iron significantly enhanced the decomposition of alumina resulting in an enhanced refractory degradation as well as the formation of a new reactant product. This product was identified as a Fe–Al intermetallic phase from SEM/EDS (scanning electron microscopy/energy-dispersive spectroscopy) and x-ray microdiffraction investigations.

Commonly used pre-treatments during e-waste recycling, e.g., manual dismantling, removal of components, size reduction, crushing etc. can cause significant local area contamination and environmental pollution. This study seeks to critically assess the impact of mechanical pre-treatments on average resource recovery, generation of high-value material concentrates and on concentrations of hazardous elements. Two sets of initial processing were carried out on a variety of waste printed circuit boards (PCBs). Electronic components were not removed from these boards. In Set I, PCBs were powdered using sorting, crushing, hammering followed by separation into heavy and light fractions through froth floatation. In Set II, PCBs were cut into small sized pieces. These were heat treated in a horizontal furnace in inert atmosphere at 850 °C for 15 min, followed by in-depth characterization of pyrolysis residues. The average recovery of main metal copper was quite comparable for both sets (Set I: 27.6 wt %; Set II: 26.3 wt %). In case of precious metals, there were higher recoveries for Au and Ti in Set I, whereas Ag, Pd, Pt showed better recoveries in Set II. A mixed trend was observed for minor metals Mn, Zn Sn, Sb and Si. In Set I, most elements showed a mixed presence in the heavy and light fractions after pyrolysis. On the other hand, Set II showed a significantly higher elemental segregation and generation of high value concentrates. Potential toxic hazardous elements (Pb, Cr, Co, Cd, Be) were detected in much higher amounts in Set I as compared to Set II. Waste processing under Set II was found to be more efficient, cost-effective and eco-friendly as compared to Set I. This study suggests a fresh look at traditional labour-intensive e-waste recycling practices towards limiting social and environmental impacts while enhancing the efficiency and cost-effectiveness of resource generation from e-waste.

Spark plasma sintering (SPS) investigations were carried out on three sets of Co specimens: untreated, high energy mechanically (HEMT) pre-treated, and nanomodified powders. The microstructure, density, and mechanical properties of sintered pellets were investigated as a function of various pre-treatments and sintering temperatures (700&ndash, 1000 &deg, C). Fine-grained sinters were obtained for pre-treated Co powders, nano-additives tended to inhibit grain growth by reinforcing particles at grain boundaries and limiting grain-boundary movement. High degree of compaction was also achieved with relative densities of sintered Co pellets ranging between 95.2% and 99.6%. A direct co-relation was observed between the mechanical properties and densities of sintered Co pellets. For a comparable sinter quality, sintering temperatures for pre-treated powders were lower by 100 &deg, C as compared to untreated powders. Highest values of bending strength (1997 MPa), microhardness (305 MPa), and relative density (99.6%) were observed for nanomodified HEMT and SPS processed Co pellets, sintered at 700 &deg, C.

An in-depth investigation was carried out on five Chinese coals using a range of advanced analytical techniques focused specifically on extracting structural parameters. Detailed investigations were carried out using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction followed by peak deconvolution and data analysis. Correlations were established for parameters determined from different techniques. The FTIR data showed good linear relationships between the apparent aromaticity (fa(FTIR)) and (R/C)u with the H/C atomic ratio for all coals under investigation. These results indicate that FTIR spectroscopy coupled with appropriate data analysis can be successfully used to determine aromaticity and the coal rank. Raman spectroscopy data showed a negative linear relationship between the GL fraction and H/C ratio; no well-defined relationship was observed between other band fractions and the H/C ratio. The decrease of AD/AG with increasing H/C ratio indicates the growth of ...

Large number of waste automotive tyres are being disposed through landfill or illegally dumped and only small proportions are currently recycled. Waste tyres can be a source of health and environmental concerns and also represents a loss of potential valuable source. The ecofriendly and resource recovery approach is critically required to recycle waste automotive tyres. In this paper, an attempt to synthesis SiC/Si 3 N 4 nanocomposite by in situ process using automotive waste tyres as resources has been reported. The synthesis was carried by using simultaneous carbothermal reduction and nitridation reaction at 1550 °C in nitrogen atmosphere using pyrolysed waste automotive tyre char as carbon source and silicon dioxide as silica source. The formation of SiC and Si 3 N 4 particles was confirmed by FTIR and XRD techniques. Raman analysis signifies the major phases of β-SiC, α-Si 3 N 4 and β-Si 3 N 4 . The particle size of synthesised SiC/Si 3 N 4 nanocomposite was in the range of 20–100 nm and mainly composed of sphere shaped nanoparticles. This innovative approach of using automotive tyres as carbon source for synthesising SiC/Si 3 N 4 nanocomposite will reduce the volume of wastes in landfills, decreases the risk of health concerns and also recovers valuable carbon resource.

We report the generation of novel carbon micro fibers and foam structures during the pyrolysis of polymer rich waste printed circuit boards (PCBs) in the temperature range of 750 °C to 1550 °C under argon atmosphere. Following initial polymer degradation and the separation of most of the metallic phase, the carbonaceous residue was seen to evolve into a variety of structures. Carbon fibers started to nucleate ~ 1150 °C, had a thickness ranging between 2 and 10 microns, contained up to 95% C with morphologies ranging between tubular, foamy network and fibrous. The chemical compositions of these carbon structures was determined through X-ray microanalysis; the carbon content was close to 90% along with 5–7% oxygen, traces of phosphorus, antimony, tin and copper. The transformation of carbon fibers to a well-defined foam structure was observed at 1250 °C; these structures were found to be stable even at higher temperatures. The formation of carbon foams/fibers was found to be not very sensitive to the relative concentration of oxide impurities present. This study shows that a potentially vast source of carbon could be recovered from the non-metallic fraction of e-waste for applications such as reduction reactions, carburization, metal–carbon composites or as a source of fuel and energy.

The degradation behavior of alumina (10–20 wt%) carbon refractories was investigated during high temperature (1 550 °C) contact with a ternary casting mould meniscus slag containing 50% MnO, 25% SiO2, and 25% Al2O3 and a binary slag containing 40% MnO and 60% SiO2. Using the sessile drop approach, the transient progress of corrosion reactions was investigated as a function of time and refractory composition. An in-depth characterization and analysis of reacted assemblies was carried out using optical and scanning electron microscopy (SEM). Optical micrographs showed a significant penetration of both slags within the refractory substrate, with very little slag remaining behind after 15 min of contact. The depth of penetration of ternary slag was found to increase with carbon concentration in the refractory. An all-round corrosion was observed with extensive refractory degradation over a period of time. Corrosion was determined to a great extent by dissolution reactions in the interfacial region; alumina dissolution from the refractory resulted in the formation of needle-like corundum crystallites which transformed to a cohesive network of faceted corundum crystals on extended contact. A number of reaction products containing Mn and Si were also observed.

A series of adsorption–alkalization experiments were conducted in a muffle furnace on two types of blast furnace cokes at 1300 °C in the presence of alkali vapors. Coke textures were found to peel off layer by layer after the alkalization process by potassium vapor, and macro fissures were observed for K/Coke ratios higher than 3/100. This phenomenon was not observed in the coke samples alkalized by sodium vapor. A number of additional potassium-bearing and sodium-bearing phases were detected with scanning electron microscope and energy dispersive spectrometer after the alkalization process. The formation of kalsilite or potassium aluminum silicate (KAlSiO4) and sodium alumina silicates (Na6Al4Si4O17) was confirmed through X-ray diffraction, however the formation of intercalation compounds that were expected to form in the alkalized coke samples could not be confirmed. The catalytic effect of sodium and potassium-bearing minerals appeared to be quite similar; the degradation of coke strength by sodium was however found to be stronger than that caused by potassium. The severe degradation of coke quality caused by alkali vapors was attributed to their strong influence on the coke carbon matrix, coke minerals, as well as their catalytic effect on the carbon gasification reaction.

High-temperature transformation studies were carried out on polymer-rich waste printed circuit boards (PCBs) in the temperature range of 750–1,350 °C in argon atmosphere. Copper-rich metallic fractions started to separate out as foils/droplets at temperatures above 950 °C producing significant quantities of carbonaceous residue. In-depth characterisation of the residue was carried out using X-ray diffraction, Raman spectroscopy, SEM/EDS, surface area analysis, and LECO measurements. The recovery of carbons from waste PCBs reached up to 25 % of total weight. These carbons generally had a disordered structure with 3–4 layers stacking along the c-axis. The presence of metals in the carbonaceous residue became negligibly small at 1,350 °C, significantly enhancing the quality of the carbonaceous product (carbon content: 52–74 wt%). This study has shown that potentially vast reserves of carbon could be recovered from e-waste through appropriate recycling, while minimising the impact of waste on the environment.

The exploration, understanding and potential applications of ‘Carbyne’, the one-dimensional sp allotrope of carbon, have been severely limited due to its extreme reactivity and a tendency for highly exothermic cross-linking. Due to ill-defined materials, limited characterization and a lack of compelling definitive evidence, even the existence of linear carbons has been questioned. We report a first-ever investigation on the formation of carbyne-like materials during low temperature pyrolysis of biobased lignin, a natural bioresource. The presence of carbyne was confirmed by detecting acetylenic –C≡C– bonds in lignin chars using NMR, Raman and FTIR spectroscopies. The crystallographic structure of this phase was determined as hexagonal: a = 6.052 Å, c = 6.96 Å from x-ray diffraction results. HRSEM images on lignin chars showed that the carbyne phase was present as nanoscale flakes/fibers (~10 nm thick) dispersed in an organic matrix and showed no sign of overlapping or physical contact. These nanostructures did not show any tendency towards cross-linking, but preferred to branch out instead. Overcoming key issues/challenges associated with their formation and stability, this study presents a novel approach for producing a stable condensed phase of sp-bonded linear carbons from a low-cost, naturally abundant, and renewable bioresource.

The environmentally sustainable disposal and recycling of ever increasing volumes of electronic waste has become a global waste management issue. The addition of up to 25% polymeric waste PCBs (printed circuit boards) as fillers in polypropylene (PP) composites was partially successful: while the tensile modulus, flexural strength and flexural modulus of composites were enhanced, the tensile and impact strengths were found to decrease. As a lowering of impact strength can significantly limit the application of PP based composites, it is necessary to incorporate impact modifying polymers such as rubbery particles in the mix. We report on a novel investigation on the simultaneous utilization of electronic and automotive rubber waste as fillers in PP composites. These composites were prepared by using 25 wt.% polymeric PCB powder, up to 9% of ethylene propylene rubber (EPR), and PP: balance. The influence of EPR on the structural, thermal, mechanical and rheological properties of PP/PCB/ EPR composites was investigated. While the addition of EPR caused the nucleation of the β crystalline phase of PP, the onset temperature for thermal degradation was found to decrease by 8%. The tensile modulus and strength decreased by 16% and 19%, respectively; and the elongation at break increased by ~71%. The impact strength showed a maximum increase of ~18% at 7 wt.%–9 wt.% EPR content. Various rheological properties were found to be well within the range of processing limits. This novel eco-friendly approach could help utilize significant amounts of polymeric electronic and automotive waste for fabricating valuable polymer composites.

Light-weight ferro-aluminium alloys are finding increasing application in the transport sector to reduce overall weights, energy costs and CO2 emissions. As the primary production processes of both Fe and Al are among the most energy-intensive industrial processes in the world, there is an urgent need to develop alternate routes for producing Fe-Al alloys. Our group has successfully produced these alloys in the Fe2O3-Al2O3-C system by producing molten iron in situ, followed by the reduction of alumina at 1550 °C and pick-up of Al by Fe. In this article, we report on the influence of silica, a typical impurity present in iron oxide and reductant carbon, on the reduction reactions in this system, and on the formation of ferroalloys. In-depth investigations were carried out on the Fe2O3-SiO2-C and Fe2O3-Al2O3-SiO2-C systems at 1550 °C for times of up to 60 min. Detailed HRSEM/EDS and XRD analysis was carried on the quenched reaction products recovered after various heat treatments. A complete reduction of silica and alumina was observed in the Fe2O3-SiO2-C system, along with the formation of FeSi and SiC. The reduction reactions were relatively slow in the Fe2O3-Al2O3-SiO2-C system. While the formation of SiC, FeSi and mullite (Al6Si2O13) was observed, even small amounts of Fe-Al alloys could not be detected. The presence of silica impurities reduced the formation of Fe-Al to negligible levels by depleting molten iron from the reaction zone, a key ingredient for the low-temperature carbothermic reduction of alumina. This study shows that some impurities can be highly detrimental to the reaction kinetics and the formation of ferroalloys, and great care needs to be exercised during the choice of reaction constituents.

We report an investigation on the corrosion behavior of ZrO2–graphite insert in submerged entry nozzles (SEN) during its high temperature interaction with the mould flux focused specifically on the role of glaze coating. A detailed metallographic examination of the representative samples collected at different stages of its usage was carried out to examine the transient progress of corrosion. The interaction between the glaze material and the base refractory at the typical preheating temperature of SEN initiated the degradation of the partially stabilized ZrO2 grains due to the formation of reaction products. Clear evidence is presented to show that the reaction product and the original layer of glaze coating survived after 90 min of casting. Early stages of corrosion involved the progressive congruent dissolution of reaction products and the residual glaze phase into the mould flux. Due to the absence of the glaze layer in the later stages of operation (480 min), corrosion was caused by the fragmentation of the aggregate phase and structural damage. This work highlights the importance of compositional control and coating thickness of the glaze material on the ZrO2–graphite refractory insert.

Sessile drop investigations were carried out on Al2O3-12.9C refractory substrates in contact with molten iron at 1823 K (1550 °C) for 30 minutes. Chemical reactions in this system resulted in the generation of trace quantities of ferro-aluminum alloys. An X-ray micro-diffraction approach was developed to localize and structurally identify these phases based on epitaxial mapping using X’Pert materials research Diffractometer. Using this technique, a small peak in the standard XRD pattern could be enhanced to four diffraction peaks with much higher intensities, leading to a much improved indexing of diffraction peaks and structural characterization of the reaction product.

The rapid consumption and obsolescence of electronics have resulted in e-waste being one of the fastest growing waste streams worldwide. Printed circuit boards (PCBs) are among the most complex e-waste, containing significant quantities of hazardous and toxic materials leading to high levels of pollution if landfilled or processed inappropriately. However, PCBs are also an important resource of metals including copper, tin, lead and precious metals; their recycling is appealing especially as the concentration of these metals in PCBs is considerably higher than in their ores. This article is focused on a novel approach to recover copper rich phases from waste PCBs. Crushed PCBs were heat treated at 1150 °C under argon gas flowing at 1 L/min into a horizontal tube furnace. Samples were placed into an alumina crucible and positioned in the cold zone of the furnace for 5 min to avoid thermal shock, and then pushed into the hot zone, with specimens exposed to high temperatures for 10 and 20 min. After treatment, residues were pulled back to the cold zone and kept there for 5 min to avoid thermal cracking and re-oxidation. This process resulted in the generation of a metallic phase in the form of droplets and a carbonaceous residue. The metallic phase was formed of copper-rich red droplets and tin-rich white droplets along with the presence of several precious metals. The carbonaceous residue was found to consist of slag and ∼30% carbon. The process conditions led to the segregation of hazardous lead and tin clusters in the metallic phase. The heat treatment temperature was chosen to be above the melting point of copper; molten copper helped to concentrate metallic constituents and their separation from the carbonaceous residue and the slag. Inert atmosphere prevented the re-oxidation of metals and the loss of carbon in the gaseous fraction. Recycling e-waste is expected to lead to enhanced metal recovery, conserving natural resources and providing an environmentally sustainable solution to the management of waste products.

In this paper, the work dealt with the characterisation of chars obtained by rapid pyrolysis of waste compact discs (CDs) at different temperatures and its application as reductant in ironmaking industries. The rapid pyrolysis was performed at atmospheric pressure and temperatures ranging from 550 to 1550 °C. The obtained chars were characterised by ultimate analysis, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS), N 2 isothermal adsorption method and scanning electron microscopy (SEM). The results indicated that char structure changed upon different pyrolysis temperature. The char yield decreased from 22% to 18% and gradual increase in carbon/oxygen ratio was observed with increase in pyrolysis temperature from 550 to 1550 °C. The porosity in chars increased progressively with pyrolysis temperature, and maximum development of pores appeared at 850 °C with surface area 334 m 2 /g. At higher pyrolysis temperature, the chars became more aromatic and ordered, and aliphatic structures decreased significantly. The loss of functional groups at higher temperature such as carbonyl, aliphatic C H was evident by FTIR, XPS and Raman results. The ordered char structure obtained at 1550 °C was used as reductant carbon for iron oxide reduction process, and 90% reduction was achieved. The waste CD char obtained during pyrolysis indicates as a valuable supplementary carbon source for ironmaking industries.

The implementation of pulverized coal injection technology has resulted in the reduction in the amounts of coke being used in the blast furnace, which has led to increased demands for high quality cokes to provide enhanced performance. Under the twin pressures of resource shortage of coking coals and continuous requirements for improved coke quality, an in-depth understanding of coke behavior in blast furnace has become very important and pertinent. This review article is focused on a comprehensive investigation on the evolution of structural order, microstructure and mineral matter of metallurgical coke in a blast furnace and presents various mechanisms of coke degradation during its descent in a blast furnace toward establishing reference standards for coke quality and performance. Coke structure, microstructure and reactivity were investigated as a function of temperature, its location in the blast furnace and under the influence of alkalis above the tuyere level. The transformation of coke in the blast furnace hearth and its dissolution into hot metal were also reviewed. The current indices for evaluating coke quality were examined based on the modifications of coke structure, and several unresolved issues in the field requiring further research were identified. This literature survey has shown that while crystalline order and microstructure had a strong influence on carburization, gasification reactions and the strength of coke, factors such as mineral matter, alkalis, temperature were among some of the important factors that affected the degradation of coke in a blast furnace.

Around the world the amount of electronic waste is growing exponentially and considered to be an important environmental and health issue. The environmental friendly and resource recovery methodology is critically required for existing scenario to recycle electronic waste. In this paper, a novel approach to synthesise silicon carbide (SiC) nanoparticles by using electronic waste compact discs (CDs) char as a carbon source is reported. The synthesis is based on carbothermal reduction at 1550 °C using waste CD char as the carbon source and silicon dioxide as the silicon source. FTIR, Raman and XPS results confirm the formation of SiC particles and XRD signifies the major phases of 3C-SiC. The size of synthesised SiC particles was in the range of 40–90 nm and was mainly composed of sphere shaped nanoparticles. This innovative approach of using electronic waste CDs as the carbon source for synthesising SiC nanoparticles will reduce the volume of waste in landfills and also the dependency of industries on traditional raw materials.

Molecular dynamics (MD) simulations were carried out to investigate the melting transition of iron with an aim to determine the accuracy and reliability of simulated melting points (MP), computing efficiency, and the role played by initial configurations. Two simulation techniques with equilibrium and non-equilibrium heating, and two well-known potentials: Mendelev (EAM) and Etesami (MEAM) were used to investigate a variety of initial configurations containing perfect crystal solid lattice and solid-liquid (S-L) coexistence regions with a number of S-L interfaces and relative S-L proportions (PC, SLSS-2, SLSS-4, SLSS-2 (20%L) and SLSS-2(80%L)). The simulated magnitude of MPs using the non-equilibrium heating method was found to be ~2020 K, which is about 200 K higher than experimental MP of iron (1811 K). Similar values were obtained for both potentials, PC and SLSS-2 configurations; there was a strong evidence for hysteresis effects as well. Simulations with equilibrium heating technique showed that MPs were found to be identical for the wide range of S-L configurations investigated: Mendelev potential (1769 ± 1 K) and Etesami potential (1811 ± 1 K). Corresponding results from the purely solid PC configurations were found to be much higher (1981 ± 1 K and 1951 ± 1 K respectively). Results on other system properties including pair distribution functions, density, local melting and solidification are also reported. These studies have helped identify optimal simulation parameters, potentials and computational approaches to probe the melting region of iron towards applications to problems of industrial importance.

A possible reaction mechanism is presented for the low temperature carbothermic reduction of alumina in the presence of molten iron under inert conditions. This reduction was found to take place in ...

Rapid urbanization, a general improvement in living standards and increased consumption has resulted in the generation of unprecedented amounts of waste in recent years. Among different wastes, electronic wastes (e-waste) volumes are growing three times faster than any other forms of urban waste. It is estimated that 20 to 50 million tonnes of e-waste are generated worldwide every year. E-waste contains over 1000 different substances; some are toxic and hazardous, which cause serious problems to environment and on human health. Generation of waste residues during recovery of precious metals from e-waste, the presence of hazardous lead, waste plastics, secondary pollution caused by landfilling non-metallic residues are some of the problems associated with recycling e-waste. We report a novel approach to recover valuable materials from waste printed circuit boards; controlled pyrolysis of e-waste was carried out at high temperatures (750-1550 °C) in an argon atmosphere. Segregation of lead and other metals was investigated as a function of temperature and reaction products were analyzed using Inductively Coupled Plasma spectroscopy and Scanning Electron Microscopy. Temperatures above 1350 °C were required to completely remove lead and other metals from e-waste; waste residue that was left behind was predominantly composed of carbon. Further research was carried out on the utilization of lead free non-metallic residue as a carbon source in ironmaking application. Non-metallic residual waste from recycling PCB was found to be a promising reductant in ironmaking applications. This research has laid the foundations of a ‘Zero Waste’ approach for managing and recycling electronic waste.