High-value Recovery Research Articles

High-efficiency simultaneous extraction of rare earth elements and iron from NdFeB waste by oxalic acid leaching

Iron can not be recovered at high value because only rare earth elements are effectively recovered from NdFeB waste via oxidation roasting-hydrochloric acid leaching process. In this study, a new method for leaching NdFeB waste with oxalic acid was developed. The high-efficiency, simultaneous and high-value recovery of rare earth elements and iron was realized to simplify the process and improve the economic benefit. Results of the oxalic acid leaching experiments show that under the optimum leaching conditions at 90 °C for 6 h in the aqueous solution of oxalic acid (2 mol/L) with a liquid–solid ratio of 60 mL/g, the iron leaching efficiency and precipitation rate of rare earth oxalate reach 93.89% and 93.17%, respectively. Rare earth oxalate and Fe(C2O4)33− were left in the residue and the leaching solution, respectively. The leaching mechanism was further analyzed by characterising the leach residues obtained through X-ray powder diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Results of the leaching kinetics study indicate that the process of oxalic acid leaching follows the shrinking nucleus model, and the leaching kinetics model is controlled by the mixed factors of diffusion and chemical reaction. The leaching residue was calcined at 850 °C for 3 h and then decomposed into rare earth oxide, which can be directly used to prepare rare earth alloy via molten salt electrolysis. For the leaching solution, ferric oxalate solution was reduced using Fe powder to prepare the ferrous oxalate (FeC2O4·2H2O).

Economic and environmental benefits of recovery networks for WEEE in Europe

The EU directive on Waste Electrical and Electronic Equipment (WEEE) imposes the obligation to collect a large share of the end-of-life products on electronics manufacturers. Environmental aspects, however, are often considered only rudimentarily. Based on previous research and real-world data, a mixed-integer linear programming (MILP) model of a European reverse network for WEEE is developed, including collection, high-value recovery, or third-party collection and recycling. The results comprise optimal network decisions and corresponding opportunity costs for economic and 21 environmental categories (18 midpoints, 3 endpoints). The evaluation of the environmental impact is based on data from the ecoinvent database, characterized using the ReCiPe 2016 Life Cycle Impact Assessment (LCIA) method. The results unveil conflicts and congruencies between the objectives. Collection and high-value recovery are preferable in up to six countries for economically optimal networks and in up to 15 countries with optimal benefit for global warming and fossil resource depletion. Discrepancies in objective values are larger between economic and most of the environmental solutions than in between most of the environmental ones. The dimensions land use and freshwater eutrophication show the least conflicts with the economic rationale. Solutions for mineral resource depletion prefer third-party collection and recycling. Conflicts between solutions are resolved by the ε-constraint method. Sensitivity analyses show the robustness of key findings. This study emphasizes the importance of a broad assessment of environmental impacts as well as mutual economic and environmental opportunity costs in large-scale recovery networks for WEEE.

Recovering large Brownfield projects in distress

A large body of knowledge exists about how to plan and establish projects for success; from project management guidelines to staged gate-execution methodologies. Despite such prescriptive means to guarantee project success, the upstream oil and gas industry has a poor track record for delivering large projects. Little guidance exists on how to restore delivery assurance to partially executed projects in distress. Furthermore, recovery efforts for large brownfield projects, mid-way through their execution, are further complicated and highly constrained. Operators and contractors alike are understandably concerned about the high failure rate of projects, particularly as Australia competes for global capital in the final investment decision for a project’s development. Issues cover the full spectrum of safety, cost, schedule, start-up, and operability. Furthermore, unanticipated issues such as industrial relations, resourcing, project controls, estimate basis, and design changes all play a central role in why projects find themselves in distress. In a recent case study, a structured recovery approach restored delivery assurance to a $900 m upstream brownfield project. Despite the numerous challenges encountered during the recovery efforts, the project went on to deliver ahead of its revised cost and schedule commitment, while also achieving outstanding safety performance. The self-governance program was instrumental in restoring delivery performance through responsive decision making that was robust, repeatable and preserved free calendar time for early intervention on high value recovery issues. The journey of recovery also restored a fractured client and contractor relationship by fostering a project delivery environment that was highly collaborative.

Use of supply relationships to recycle secondary materials

The reverse logistics function in supply chain management has received increasing attention in recent years as the value of the activity, the awareness of its potential and the legal requirements for its presence have increased. Reverse logistics has two dominant end purposes for returned materials–reconditioning (high-value recovery) or recycling (low to no value recovery). Much of the material generated by reverse logistics activity falls into this second category of low to no value. This can create a significant material management problem for many organisations. Several large organisations have successfully created recycling empires around the more primary materials that feed readily into raw material supply streams–such as metals, timbers and paper. For individual firms, however, the likelihood of investing effort in identifying both materials that could be recycled and a potential market for them has seemed frequently out of reach. This study highlights an under-researched phenomenon whereby firms engage with one another to seek economical recycling of low value and often complex secondary materials. Using eight case studies of manufacturing firms, the study identifies several examples of innovative and valuable recycling solutions occurring between supply chain members. Supply relationships are proposed to provide a critical enabler for improving firm knowledge of material value, recycling options, previously un-considered buyers or markets for a material, and for aggregating resources and improving the economy of recycling.

Linking forward and reverse supply chain investments: The role of business uncertainty

This paper explores managerial efforts in reverse supply chains (RSC), where the focus is on the capture and exploitation of used products and materials. The RSC can potentially reduce negative environmental impacts of extracting virgin raw materials and waste disposal. If so, investment in the reverse supply chain should not be made in isolation, but instead must be integrated with investments selected to improve the forward supply chain. After defining and operationalizing these constructs, a survey of plant managers was used to empirically assess the linkages between supply chain investments, organizational risk propensity (i.e., willingness to take risk) and business uncertainty. Reverse supply chain investment had two primary dimensions: reconditioning (i.e., high-value recovery) and recycling and waste management (i.e., low- or no-value recovery). Ongoing investment in the forward supply chain was significantly related to investment in recycling and waste management, but not to investment in reconditioning. Moreover, risk propensity was found to mediate the relationship between the external business uncertainty and investment in the forward and reverse supply chain.

Production speed effects on log-making error rates and value recovery for a mechanized processing operation in radiata pine in New Zealand

Mechanized processing operations are complex man-machine systems. The impacts of changes to work practices are, therefore, dependent on the effects the changes have on both the machine and the man. A mechanized processor, delimbing and cutting tree length stems into logs on a landing, was studied in two Pinus radiata plantation forest stands in New Zealand in early 2004 to determine the effect that production speed had on operator decision making and on the machine measurement accuracy and precision. The processor operator was experienced and had a reputation for high value recovery performance. The operator was asked on four occasions to process stems at different production speeds; slow, normal, fast and very fast. Over 150 stems were processed into 849 logs during the four trials. Value recovery, log-making error rates and productivity were assessed during each of the trials. It was found that production speeds ranging from 430 to 610 m3 per day had no impact on gross value recovery, the types of log...