Preparation of 97% pure nickel-cobalt alloy from waste Ni-MH batteries by using waste glass as a fluxing agent.

With the e-waste growing rapidly all over the globe due to growing demand of electronics, smartphones, etc., coming up with an efficient and sustainable recycling process is the need of the hour. The present work reports a novel and sustainable process of manufacturing Ni alloy by bringing together three major waste streams such as waste Ni-MH batteries, e-waste plastics, and waste glass. The chosen temperature (1550 °C) favours the reduction of nickel-oxide by e-waste plastic as the reductant and sends rare earth elements present in the waste Ni-MH battery as oxide mixture to the slag phase. Waste glass powder used in this process functions as the fluxing agent, hence not requiring any additional flux. The reduction mechanism is gas-based, controlled mainly by hydrogen and carbon monoxide gases released as a result of decomposition of e-waste plastic as reaction commenced from cold zone (∼300 °C) to hot zone (1550 °C) in the horizontal tubular furnace. Formation of nickel alloy and enrichment of slag with mixture of rare earth oxides were confirmed by XRD, SEM-EDS, and Rietveld refining analysis performed on the XRD spectra of slag phase. ICP-OES (Inductively coupled plasma optical emission spectroscopy) and LIBS (laser induced breakdown spectrometer KT-100S) confirmed the high metal content in the alloy, thereby emphasizing the purity (∼98%) which is close to the composition of nickel super alloy. A maximum of 61% by weight REO enrichment was achieved in the slag phase, having La2O3:44.6%, Pr2O3:14.8%, and Nd2O3: 1.6% under optimised experimental conditions (1550 °C, 15 min, and 20% waste glass powder). This scientific investigation evinces a promising route for efficient utilisation of waste streams emanating from e-waste, thereby devising a sustainable recycling technique and protecting the environment, too.

Selective synthesis of CuNi alloys using waste PCB and NiMH battery.

The aim of this study is to establish the potential novel approach for the selective synthesis of copper-nickel (CuNi) alloys using two waste streams, printed circuit board (PCB) and nickel-metal hydride (NiMH) batteries. A thermal route is established to synthesise CuNi alloys by using waste PCB, simultaneously as a Cu source and reducing agent from C-bearing polymer and waste NiMH batteries as Ni source. Thermal transformation and reduction studies were carried out at 1500 °C under an inert atmosphere. Initial characterization of raw materials was conducted in detail using various analytical techniques. Synthesised CuNi alloys were confirmed with ICP, EDS and XRD analyses. Material ratios of 75-25 wt% and 50-50 wt% of NiMH battery and PCB waste was considered and these range of compositions of e-waste, as raw materials, minimised the slag generation and optimised Ni recovery. Concentration of Nickel in the synthesised alloys was 20-30 wt%. Reduction extent of nickel oxide using PCB as reductant was confirmed by off-gas analysis. This approach has the potential to be implemented in selective synthesis of CuNi alloys instead of using conventional ores/reductant, to achieve target composition of alloys as per application requirements including marine/automotive/electronic industries. This novel approach promises significant benefits to divert e-wastes from landfill and provide sustainable solution for future metal alloy security.

Characteristics of waste automotive glasses as silica resource in ferrosilicon synthesis.

This fundamental research on end-of-life automotive glasses, which are difficult to recycle, is aimed at understanding the chemical and physical characteristics of waste glasses as a resource of silica to produce ferrosilicon. Laboratory experiments at 1550°C were carried out using different automotive glasses and the results compared with those obtained with pure silica. In situ images of slag-metal separation showed similar behaviour for waste glasses and silica-bearing pellets. Though X-ray diffraction (XRD) showed different slag compositions for glass and silica-bearing pellets, formation of ferrosilicon was confirmed. Synthesized ferrosilicon alloy from waste glasses and silica were compared by Raman, X-ray photoelectron spectroscopy and scanning electron microscopy (SEM) analysis. Silicon concentration in the synthesized alloys showed almost 92% silicon recovery from the silica-bearing pellet and 74-92% silicon recoveries from various waste glass pellets. The polyvinyl butyral (PVB) plastic layer in the windshield glass decomposed at low temperature and did not show any detrimental effect on ferrosilicon synthesis. This innovative approach of using waste automotive glasses as a silica source for ferrosilicon production has the potential to create sustainable pathways, which will reduce specialty glass waste in landfill.

Microrecycled zinc oxide nanoparticles (ZnO NP) recovered from spent Zn-C batteries for VOC detection using ZnO sensor.

Non-intrusive techniques for diagnosis and biomonitoring - for example, breath testing to detect biomarkers - have the potential to support the advancement of versatile and remote point-of-care (PoC) diagnostics. This paper investigates tuning the sensitivity and selectivity performance of chemo-resistive sensors to detect volatile organic compound (VOC) biomarkers using a hybridized material of pristine graphene (pG) and zinc oxide nanoparticles (ZnO NP) recovered from spent Zn-C batteries. This hybridized graphene nanocomposite material of ZnO nanoparticles showed enhanced sensing performance because of high conductive property of graphene along with the synergetic interplay between graphene composite materials and ZnO NPs. The elevated surface area as well as adsorption capability of ZnO NPs provided improved sensitivity and selectivity for particular VOCs. It was proposed that this hybridized material could be used to fabricate chemo-resistive sensors with sensing performances tailored for VOC biomarker detection. To test this hypothesis, the ability of graphene hybrid nanocomposites with ZnO NPs to improve the sensing characteristics and efficiency of distinguishing diverse VOC biomarkers such as ethanol, acetone, methanol, chloroform, acetonitrile and terahydrofuran (THF) was investigated. Results demonstrated that the microrecycled ZnO based hybrid sensor has good selectivity along with the sensitivity towards ethanol and chloroform VOCs at room temperature (20 °C).

Manganese oxide synthesized from spent Zn-C battery for supercapacitor electrode application.

Manganese oxide (Mn3O4) nanomaterials have promising potential to be used as supercapacitor electrode materials due to its high energy storage performance and environmental compatibility. Besides, every year huge volume of waste batteries including Zn-C battery ends up in landfill, which aggravates the burden of waste disposal in landfill and creates environmental and health threat. Thus, transformation of waste battery back into energy application, is of great significance for sustainable strategies. Compared with complex chemical routes which mostly apply toxic acids to recover materials from Zn-C battery, this study establishes the recovery of Mn3O4 particles via thermal route within 900 °C under controlled atmosphere. Synthesized Mn3O4 were confirmed by XRD, EDS, FTIR, XPS and Raman analysis and FESEM micrographs confirmed the coexistence of spherical and cubic Mn3O4 particles. Mn3O4 electrode derived from waste Zn-C battery demonstrate compatible electrochemical performance with standard materials and conventional synthesis techniques. Mn3O4 electrode exhibited highest capacitance value of 125 Fg-1 at 5 mVs-1 scan rate. The stability of the electrode showed good retention in discharge and charge capacity by about 80% after 2100 cycles. This study demonstrates that waste Zn-C battery can be further utilized for energy storage application, providing sustainable and economic benefits.

Zinc Oxide Nanoparticles from Waste Zn-C Battery via Thermal Route: Characterization and Properties.

Disposable batteries are becoming the primary sources of powering day-to-day gadgets and consequently contributing to e-waste generation. The emerging e-waste worldwide is creating concern regarding environmental and health issues. Therefore, a sustainable recycling approach of spent batteries has become a critical focus. This study reports the detail characterization and properties of ZnO nanoparticles recovered from spent Zn-C batteries via a facile thermal synthesis route. ZnO nanoparticles are used in many applications including energy storage, gas sensors, optoelectronics, etc. due to the exceptional physical and optical properties. A thermal treatment at 900 °C under an inert atmosphere of argon was applied to synthesize ZnO nanoparticles from a spent Zn-C battery using a horizontal quartz tube furnace. X-ray diffraction (XRD), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of crystalline ZnO nanoparticles. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis confirmed that the size of synthesised ZnO particles were less than 50 nm and mainly composed of sphere shaped nanoparticles. Synthesized ZnO exhibited BET surface area of 9.2629 m²/g and showed absorption of light in the UV region. Excitation of ZnO by UV light showed photoluminescence in the visible range. This study will create an opportunity for potential applications of ZnO nanoparticles from spent batteries and will benefit the environment by reducing the volume of e-waste in landfills.