Waste LCD Research Articles

Comprehensive Review for Indium Recovery from Waste LCD Panels

Comprehensive Review for Indium Recovery from Waste LCD Panels

Properties of a Low-Carbon Binder-Based Mortar Made with Waste LCD Glass and Waste Rope (Nylon) Fibers

Carbon dioxide emissions are one of the problems that arouses the interest of scientists because of their harmful effects on the environment and climate. The construction sector, particularly the cement industry, is a significant source of CO2. On the other hand, solid waste constitutes a major problem facing governments due to the difficulty of decomposing it and the fact that it requires large areas for landfill. Among these wastes are LCD waste glass (WG) and used rope waste. Therefore, reusing these wastes, for example, in concrete technology, is a promising solution to reduce their environmental impact. Limited studies have dealt with the simultaneous utilization of glass waste as a substitute for cement and rope waste (nylon) fiber (WRF). Therefore, this study aimed to partially replace cement with WG with the addition of rope waste as fibers. Thirteen mixtures were poured: a reference mixture (without replacement or addition) and three other groups containing WG and WRF in proportions of 5, 15 and 25% by cement weight and 0.25, 0.5 and 0.75% by mortar weight, respectively. Flow rate, compression strength, flexural strength, dry density, water absorption, dynamic modulus of elasticity, ultrasonic pulse velocity and electrical resistivity were tested. The results indicate that the best ratio for replacing cement with WG without fibers was 5% of the weight of cement. However, using WRF increased the amount of glass replacement to 25%, with an improvement in strength and durability characteristics.

Beneficiation and classification of ITO concentrate from waste LCD panel for industrial-scale indium extraction.

Currently, more than 55% of global indium production is consumed for indium tin oxide (ITO) production because of its excellent display properties mainly driven by demand for flat panel displays (FPDs) or LCDs. At the end of life, the waste LCD flows to the e-waste stream, accounts for 12.5% of the global e-waste, and is forecasted to be increasing progressively. These waste LCDs are potential wealth for indium that poses a threat to the environment. The volume of waste LCD generation is a global as well as national concern from a waste management perspective. Techno-economical recycling of this waste can be a panacea to the challenges associated with the lack of commercial technology and extensive research. Hence, a mass production capable of beneficiation and classification of ITO concentrate from waste LCD panels has been investigated. The mechanical beneficiation process for waste LCDs consists of five steps of operation, i.e., (i) size reduction by shredding by jaw milling, (ii) further size reduction to feed for ball milling, (iii) ball milling, (iv) classification to enrich ITO concentrate, and (v) characterization ITO concentrate and confirmation. The bench-scale process developed is intended to integrate with our indigenously developed dismantling plant (which can handle 5000 tons per annum) to handle separated waste LCD glass for indium recovery. Once scaled up, it can be integrated for continuous operation synchronized with the LCD dismantling plant.

Recovery of critical metals from leach solution of electronic waste using magnetite electrospun carbon nanofibres composite.

Scarcity in mining and geo-political direction diverts attention toward critical metal recycling. Gallium (Ga), indium (In) and germanium (Ge) are among the critical metals that consume approximately 80% of world mining in the innovative production of electrical and electronic equipment. The fast obsolescing rate generates a large amount of electronic waste, which is now seen as a secondary reservoir for critical metals. These metal resources need to be dealt with with effective recycling capabilities. Based on solid-phase extraction, magnetic nano-hydrometallurgy is opening a new area of metallic contents recovery in conventional hydrometallurgy. In the present work, polyacrylonitrile (PAN) based electrospun nanofibres were synthesized and carbonized at 800°C in an inert environment. After surface oxidation, carbon nanofibres were decorated with magnetite particles through co-precipitation. The saturation magnetization value (Ms = 23.6emu/g) confirms high loading of magnetite particles. The selected critical metal ions are freely present in an aqueous solution at pH 1 to 3; thus, highest removal efficiency was observed at pH 2. Pseudo-second-order kinetics confirm the chemical/charge interaction between sorbent and sorbate ions. Maximum sorption capacity calculated through Langmuir isotherm was 226, 191 and 171mg/g for Ge(IV), Ga(III) and In(III) metal ions, respectively. The RL value (0 < RL < 1) indicates favourable sorption process. The sorbed target metal ions were collectively eluted using 1mol/L hydrochloric acid. The preconcentration factor was calculated at 1080 for Ge(IV) and In(III) while 1260 for Ga(III). The method was validated with 5µg/mL spiked multi-element standards and applied to multiple acid-leached electronic waste samples like PCBs, waste LCD panels and solar panels. Recoveries in the range of 96.2% for Ga(III), 95.6% for In(III) and 97.4% for Ge(IV) in the presence of diverse ions indicate the suitability of the proposed method for target metal ions even in a complex matrix.

Experimental Evaluation of Properties of Concrete Made of a Combination of Regular Waste Glass and LCD Glass

Experimental Evaluation of Properties of Concrete Made of a Combination of Regular Waste Glass and LCD Glass

Full components recovery of organic matter and indium from discarded liquid crystal display panels

In the present study, organic matter and indium were fully recycled from discarded LCD panels by microwave extraction - nitrogen pyrolysis - vacuum reduction. Triphenyl phosphate, an environmentally friendly halogen-free flame retardant, was extracted from the polarizing film using microwave extraction technology. The extraction rate under optimized conditions (acetone, 55 °C, 20 min, 1:50) was 95.89%. After the microwave extraction process, the polarizing film was treated with nitrogen pyrolysis. Uncondensed pyrolysis gas/oil (mainly acetic acid) was used to prepare an environmentally friendly snow melting agent. In addition, 26.42 wt% of the pyrolytic carbon residue was obtained under the optimized conditions (350 °C, 2 °C·min−1, 0.05 L min−1, 120 min), which could be used as a reductant to recycle indium from waste LCD panels. In the vacuum reduction process, the indium conversion rate could reach 99.92% without the addition of reductant. The reaction dynamics results show that the reduction process of pyrolytic carbon and In2O3 is initially controlled by a chemical reaction, followed by a mixed control that transitions to a diffusion control. Moreover, the results of the contrast experiment show that the conversion efficiency of pyrolytic carbon to indium was comparable to that of activated carbon, and both were better than that of coke. This study can be used as a practical reference for the recycling of major components of LCD panels.

A Study of Organic Impurity Removal Efficiency for Waste LCD Touch Panel Glass by Solvents Types

본 연구에서는 LCD 터치 패널 유리의 재활용을 위해 기계적 방법과 화학적 용해법을 혼용하여 OCA 및 유기 불순물을 제거하는 실험을 진행하였다. 터치 패널의 기계적 파분쇄를 위해 cut mill과 oscillation mill을 이용하였으며, OCA와 유기 불순물의 제거를 위해 물, 에탄올, 디클로로메탄을 이용하여 터치 패널 파쇄물을 세정하였다. 세정 이후 TGA를 통해 유기 불순물의 제거 효율을 평가한 결과 디클로로메탄 단일 용매를 사용한 경우 세정 효과가 가장 뛰어났으며, 세정 온도가 증가함에 따라 유기 불순물의 제거 효과가 증가함을 확인하였다. 제타 전위 측정을 통해 터치 패널 유리 파쇄물의 용매 내 분산도를 평가한 결과, 세정 효과가 가장 낮은 물의 제타 전위 절대값이 타 용매에 비해 낮았으며, 유기물의 제거 효과는 화학적인 용해 특성뿐 아니라 용매 내 물리적인 분산 특성에 의해서도 영향을 받을 수 있음을 확인하였다.

Leaching of indium and tin from waste LCD by a time-efficient method assisted planetary high energy ball milling

The phenomenon of the long leaching time and low leaching rate is presented in the acid leaching process under the conventional conditions of low reaction temperature and acid concentration. In order to promote leaching rates of indium and tin in waste liquid crystal display, an optimized process combining rapid milling and acid leaching has been proposed, which is more time and energy-efficient, environmentally sound compared with the traditional acid leaching process. Leaching mechanism analysis was conducted to uncover the different leaching behavior of indium and tin. And the external factors affecting the leaching rates of indium and tin were studied to optimize. In this process, the fine powder with a weight ratio of 97.6%, which particle size less than 0.075 mm, was obtained with the optimal milling time of 30 min by rapid grinding in the planetary high energy ball milling. About −0.003 l/s of grinding rate constant was performed in the grinding size fraction from 3 mm to 0.075 mm. The research results indicated that the particle size less than 0.035 mm was agglomerated, and the addition of H2O2 reduced the leaching rate for the particle size less than 0.075 mm. Moreover, 86.3% and 76.1% of indium and tin were leached in a short leaching time of 10 min by using 3 M H2SO4 at 85 °C for particle size range from 0.075 to 0.035 mm, while 96.9% and 85.6%, respectively in 90 min.

Partial replacement of Ordinary Portland cement by LCD glass powder in concrete

This paper represents the properties of concrete with partial replacement of cement by LCD glass powder derived from discarded gadgets. This end of life LCD glass powder was obtained from electronic glass scrap and is used in this work after grinding to a particle size of 45 µm or less. X-ray Fluorescence spectroscopy (XRF) test indicates SiO2, Al2O3, CaO and MgO as the major oxides in the LCD glass powder. The fresh state, hardened state and durability properties of concrete show significant improvement with inclusion of waste LCD glass powder in concrete. 5% replacement of cement by waste LCD glass powder is considered as the optimal replacement level with respect to the strength studies. The compressive strength of 5% replacement is obtained as 20%, 28% and 36% higher than control specimen after 7 days, 28 days and 56 days respectively with regard to chloride ion penetration and sorptivity of concrete, 5% substitution of cement shows optimal results while 20% of partial replacement with LCD glass powder gives the better results on sulphate resistance and acid attack. In concrete, replacement of cement with pozzolanic materials such as waste LCD glass powder may be a viable option in mitigating environmental pollution through a reduction in cement consumption as well as by accommodating solid waste.

Leaching of indium from waste LCD screens by oxalic acid in temperature-controlled aciduric stirred reactor

Recovery of rare metal indium from waste LCD screens is important since its content is about 500 times of the original ore. Oxalic acid has excellent ability to leach indium from waste LCD screens, and how to achieve reactor scale operation is critical to promote indium recovery. In this study, a temperature-controlled aciduric stirred reactor (TCASR) was constructed to investigate the effects of operational conditions on the leaching efficiency of indium at reactor scale. Results showed that complete leaching was achieved in 10 min under the conditions of 0.2 mol/L oxalic acid, 300 g/L of ITO glass powder dosage, 90℃ and 500 rpm of stirring speed. Compared with the previous study, the consumption of oxalic acid decreased 3/5, ITO glass powder dosage increased by 6 times and reaction time decreased 7/9. Meanwhile, the duration of indium ion concentration was maintained for 20 min instead of decreasing immediately after reaching the peak, which was conducive to actual application. The process kinetics model illustrated that temperature played the most important role in affecting the reaction rate. The potential reason of longer indium ion concentration maintaining duration was preliminarily speculated as a faster leaching of indium than calcium result in less coprecipitation caused by calcium oxalate. Therefore, the TCASR is applicable for leaching of indium from waste LCD screens by oxalic acid due to the higher leaching efficiency, less reagents consumption and stronger processing ability.

Indium and tin recovery from waste LCD panels using citrate as a complexing agent

In this work, an environmentally-friendly leaching process for the recovery of indium (In) and tin (Sn) from LCD panel waste was investigated. Easily degradable citrates (C6H5O73−), i.e., sodium citrate and citric acid, were used as complexing agents. The morphology and composition of the species present in the LCD powder before and after the leaching processes were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The concentrations of In, Sn, and iron (Fe) present in the leachate were determined by atomic absorption spectrometry (AAS). The necessary thermodynamic conditions for achieving substantial In recovery were established by using MEDUSA software. The optimal process conditions were determined experimentally by varying the initial citrate concentration as well as by using reducing or oxidizing media, respectively hydrazine (N2H4) or hydrogen peroxide (H2O2). It was found that using N2H4 in a citrate solution as a reducing agent enhances the leaching efficiency. However, high concentrations of Sn and Fe with respect to In were found in the LCD powder. Therefore, a pretreatment processes to first remove the excess of Sn and Fe, which compete with In for the citrate, was implemented. Leaching with 1 M citrate, 0.2 M N2H4, at pH = 5, using sodium hydroxide (NaOH) at solid:liquid (S:L) ratio of 20 g∙L−1, yielded a remarkably high In recovery of 98.9% after 16.6 h.

Optimization of Electrochemical Performance of Waste LCD Glass-Derived Silicon As Anodes for Lithium Ion Batteries

Silicon has been widely studied as a promising alternative that can replace graphitic anodes owing to its high theoretical specific capacity of 3580 mA h g-1 and appropriate working voltage (~0.1 V vs. Li/Li+) for lithium ion battery (LIB) anodes [1]. Recently, the industrial wastes such as windshields, glass bottles, and rice husks have been utilized as a low cost and eco-friendly Si source [2,3,4]. Waste LCD glass-derived silicon is one of the attractive candidate and this materialization technique also can be a future green technology for resolving an immense LCD waste and insufficient recycling process [5]. In this study, high purity Si were fabricated as LIB anode materials using waste LCD glasses via magnesiothermic reduction. Firstly, we eliminated containing inert impurities (Al2O3, CaO, B2O3, In2O3 etc.) by ball-milling and acid leaching. Then, pre-treated waste LCD glasses were reduced to Si particles at 650 °C for 6 hours in Ar through magnesiothermic reduction and subsequent acid treatment. As the crystallographic analyses, waste LCD glasses were successfully reduced to highly crystalline and pure Si. Waste LCD glass derived Si electrodes exhibited the high initial discharge capacity of 4290 mA h g-1. However, the capacity decreased rapidly, indicating that the electrode underwent rapid pulverization due to drastic volume expansion/fracture upon cycling [6]. To overcome this problem, diverse strategies have been proposed including nanostructuring, incorporating with carbon mediums, and post-processing of the electrode [2,7]. Herein, we elevate the electrochemical performance of waste LCD derived Si through carbon coating and electrode post-processing, that called maturation [7]. Firstly, obtained Si materials were coated by carbon using sucrose at 800 °C in Ar. Then, the electrode was matured by storing it in chamber at ~99% relative humidity for 2 days. The prepared Si electrodes exhibit much better cycling stability than untreated electrodes. This improvement originated from coated carbon and maturation process, which strengthens the cohesion of active materials and the adhesion of active material/current collector, thus less pulverization of the electrode.

Removal and recovery attempt of liquid crystal from waste LCD panels using subcritical water

With the advancement of the fourth industrial revolution, the demand for LCD has widely accelerated as monitoring screens for computers and cell phones. Consequently, old LCD panels are expected to end up as a tremendous amount of e-waste. Apart from transparent electrodes and transistor, waste LCD panel also contains hazardous liquid crystal compound that can contaminate the landfill site. Thus, removing the material from waste LCD was investigated. In this study, water at subcritical state was applied at temperatures between 100 and 360 °C. Initially, the liquid crystals were extracted using toluene and were used to compare with subcritical water. The specific compounds of the liquid crystals were not identified. The liquid crystals (12 mg/g-LCD) were entirely removed from the LCD panel when treated above 300 °C by means of extraction with the subcritical water. Although liquid crystal was successfully removed, recovery was complicated due to the degradation of liquid crystals above 250 °C. A recovery of 70% was obtained at 250 °C without deformation of the molecules. Consequently, this study has shown that although it is not practical to recover LC from LCD panel waste using subcritical water, liquid crystals can be removed efficiently. This method is auspicious in reducing hazardous liquid crystal from waste LCD panel before their disposals at landfill sites.

Degradation process regulation of waste LCD panel to ensure the remain of indium in solid phase by hydrothermal reaction.

The environmental risks and recycling potential of organic materials and indium of waste LCD panel has produced commercial value. It has been found that hydrothermal reaction can achieve an efficient and clean degradation of organic materials in a closed environment. However, as the degradation process occurs, the glass substrate is gradually exposed to the hydrothermal environment. Whether the metal indium is dissolved into the liquid phase and whether it affects product quality and the subsequent leaching process need to be discussed. In present study, simultaneous organic materials degradation and pretreatment of indium recycling was achieved due to the regulation of parameters. Effects of reaction temperature, reaction time, H2O2 supply and pH of the reaction solution on the transfer of indium in liquid and solid phase were investigated. The results showed that the degradation rate of the organic material reach 90% under the neutral condition of 300℃ of reaction temperature, 36 mL of water and 7.2 mL of H2O2 supply and 11 min of reaction time. This pretreatment method effectively realized the resource recovery of waste LCD panel and the outflow of metal indium was inhibited at the same time, thus further comprehensive recycling of resources could be prepared.

Controllable Formation of Carbon Fiber in Pyrolysis Process of Liquid Crystals from Waste LCD Panels and Indium Recovery by Vacuum in Situ Reduction with Carbon Fiber

The contradiction of energy, resource, and environment from waste LCD panels is prominent because they contain both harmful liquid crystals and the valuable resource indium. However, traditional whole crush technology is difficult to realize sustainable recycling of waste LCD panels due to a challenge from the low concentrations of liquid crystals and indium. Secondary pollution inevitably occurred in recycling process. In this work, a stripping product enriched in liquid crystals and indium was first gained by a mechanical stripping separation. Then, liquid crystals were reused as carbon source in pyrolysis process to form carbon fiber in control. Carbon fiber clusters can form well under the optimal condition of 500 °C, with 30% molecular sieve (particle size < 0.3 mm) and pyrolysis time of 15 min. The pyrolysis mechanism of liquid crystals and the formation mechanism of carbon fiber were discussed. Finally, vacuum in situ reduction of indium oxide from stripping product with the prepared carbon fiber c...

C, H, Cl, and In Element Cycle in Wastes: Vacuum Pyrolysis of PVC Plastic To Recover Indium in LCD Panels and Prepare Carbon Coating

Resource recycling of millions of solid wastes is a world’s problems. Because element is the basic unit of all wastes, the essence of wastes recycling is to realize cycle of elements in wastes. In this paper, a new concept of element cycle in wastes is proposed. Under guidance of element cycle, various wastes have common connection point. The concept is clarified by a case of C, H, Cl and In element cycle from waste PVC plastic and LCD panels. In this paper, a vacuum pyrolysis of waste PVC was proposed to recycle indium in LCD and synchronously prepare carbon coating. Cl in PVC combined with In in LCD was mainly regenerated in the form of InCl3. Meantime, C and H in PVC were reused to prepare carbon coating and energy products, such as pyrolysis oil and gas. The recycling system means to change two kinds of wastes into resources by their own element characteristics. Under optimized conditions, recovery rate of indium exceeded 98 %. Meantime, with increasing temperature, microstructure of carbon coating is...

Treatment of liquid crystals and recycling indium for stripping product gained by mechanical stripping process from waste liquid crystal display panels

In the past, most of technologies adopted whole crush for waste LCD panels to treat liquid crystals and indium but had low recovery due to its low concentration. In this work, a mechanical stripping process was proposed firstly to gain stripping product enriched liquid crystals and indium. Liquid crystals are enriched from 0.3 wt% in waste LCD panels to 53 wt% in the stripping product. Likewise, indium is enriched from 0.02 wt% to 7.95 wt%. Liquid crystals in stripping product should be removed in advance since it is disadvantage for indium recovery. This study can successfully remove liquid crystals by pyrolysis process. The results were summarized as follows: (i) Liquid crystals in waste LCD panels were mainly TFT type liquid crystals by thermal gravimetric analysis and chromatograph-mass spectroscopy. (ii) Liquid crystals can be well separated under optimized condition of 873 K, 40 min and 2 L/min N2 flow rate. Oil and gas produced in pyrolysis process can be reused as energy and fuel. (iii) Pilot scale experiments were utilized to assess the actual effect of pyrolysis separation; decomposition rate of liquid crystals can reach 80%. It gives some valuable information for industrial separation of liquid crystals and provides a necessary preparation for further recovery of indium.

Synthesis of Zeolite from Waste LCD Panel Glass

Synthesis of Zeolite from Waste LCD Panel Glass

폐 LCD판넬로부터 붕규산유리 발포체 제조를 위한 원료 유리 제조

사용 후 발생되는 폐 LCD판넬용 유리의 재활용 방안을 마련하고자 별도의 전처리 없이 폐 LCD판넬을 습식분쇄함으로서 발포체 제조용 원료유리로 사용가능한 폐 붕규산유리의 회수 방법을 조사하였으며, 이렇게 회수된 폐 붕규산유리를 사용하여 발포체의 제조를 시도하였다. 입도 270 mesh 이하의 크기로 분쇄 조절된 폐 붕규산유리를 대상으로 폐 붕규산분말 100 g에 대해 발포제로서 탄소분을 0.3 중량 분율, 추가 발포조제로서 <TEX>$Na_2CO_3$</TEX>, <TEX>$Na_2SO_4$</TEX>, <TEX>$CaCO_3$</TEX>를 각각 1.5 중량 분율이 되도록 첨가한 원료 유리분말을 발포소성온도 <TEX>$950^{\circ}C$</TEX>에서 20 min간 발포를 진행함으로서 밀도가 <TEX>$0.3g/cm^3$</TEX> 이하되는 발포체를 제조할 수 있었다. 또한 원료 유리에 추가적으로 <TEX>$SiO_2$</TEX> 또는 <TEX>$H_3BO_3$</TEX>를 첨가함으로서 얻어지는 발포체에 효과적으로 개기공을 형성할 수 있었으며, 개기공의 형성은 흡음 등 새로운 기능을 가진 발포체의 제조 가능성을 보여주었다. In this article, the foamed body of glass was manufactured from the waste borosilicate glass produced by wet pulverization process without additional pretreatment which can be used as a recycling method for waste LCD panel glass. Each 100 g of pulverized waste borosilicate glass with the size of less than 270 mesh were mixed with 0.3 weight fraction of carbon and 1.5 weight fraction of <TEX>$Na_2CO_3$</TEX>, <TEX>$Na_2SO_4$</TEX> and <TEX>$CaCO_3$</TEX> and let them foamed for 20 minutes at <TEX>$950^{\circ}C$</TEX> to manufacture the foamed body having the density of less than <TEX>$0.3g/cm^3$</TEX>. Additionally, adding <TEX>$SiO_2$</TEX> or <TEX>$H_3BO_3$</TEX> to the mixture enabled the foamed body to have efficient formation of open pores which showed the possibility for producing the foamed body with new functionalities such as sound absorption.

A study of the fresh properties of Recycled ready-mixed soil materials (RRMSM)

Climate anomalies in recent years, numerous natural disasters caused by landslides and a large amount of entrained sands and stones in Taiwan have created significant disasters and greater difficulties in subsequent reconstruction. How to respond to these problems efficaciously is an important issue. In this study, the sands and stones were doped with recycled materials (waste LCD glass sand, slag powder), and material was mixed for recycled ready-mixed soil. The study is based on security and economic principles, using flowability test to determine the water-binder ratio (W/B=2.4, 2.6, and 2.8), a fixed soil: sand ratio of 6:4 and a soil: sand: glass ratio of 6:2:2 as fine aggregate. Slag (at concentrations of 0%, 20%, and 40%) replaced the cement. The following tests were conducted: flowability, initial setting time, unit weight, dropweight and compressive strength. The results show that the slump values are 220 -290 mm, the slump flow values are 460 -1030 mm, and the tube flow values are 240-590 mm, all conforming to the objectives of the design. The initial setting times are 945-1695 min. The unit weight deviations are 0.1-0.6%. The three groups of mixtures conform to the specification, being below 7.6 cm in the drop-weight test. In the compressive strength test, the water-binder ratios for 2.4 are optimal (13.78-17.84 kgf/cm2). The results show that Recycled ready-mixed soil materials (RRMSM) possesses excellent flowability. The other properties, applied to backfill engineering, can effectively save costs and are conducive to environmental protection.