Cathode Ray Tube Funnel Glass Research Articles

Experimental investigation on the durability performances of concrete using cathode ray tube glass as fine aggregate under chloride ion penetration or sulfate attack

Cathode ray tube (CRT) funnel glass has been used to partially or totally replace natural sand as fine aggregate in concrete. It is an effective and environmentally friendly method of recycling the increasing number of discarded CRT in the electronic industry. However, little research has been performed on its durability performance under environmental attacks, in particular in the areas of chloride ion penetration and sulfate attack, the two major environmental attacks on reinforced concrete structures. This study presents an experimental investigation on the durability performances of concrete using CRT funnel glass as fine aggregate in 8% sodium chloride solution, 5% sodium sulfate solution and 10% sodium sulfate solution. Four volume replacement ratios (the ratio of CRT glass to natural sand), i.e. 0%, 30%, 60%, 100%, are considered. The chloride ion content along concrete depth direction, compressive strength and elastic modulus of concrete was measured with attack time. The test results show that although the compressive strength and elastic modulus decrease with increasing content of CRT funnel glass in concrete, the long-term resistance to chloride ion penetration is enhanced by using CRT funnel glass as fine aggregate. Furthermore, the compressive strength, rather than dynamic elastic modulus of concrete containing CRT glass, is more sensitive to sulfate attack. The relative increase in strength of CRT glass concrete is obviously larger than that of control concrete under sulfate attack. This study also provides a reference for the durability design of concrete structures using CRT funnel glass as fine aggregate.

Dynamic mechanical analysis of cement mortar prepared with recycled cathode ray tube (CRT) glass as fine aggregate

Using recycled cathode ray tube (CRT) funnel glass as a substitute for sand contributes to both reducing natural aggregate consumption and the disposal of CRT funnel glass. Currently, most studies have focused on the mechanical and durability properties of mortar or concrete containing CRT glass as fine aggregate. However, the study of the dynamic loadings (e.g., earthquake load, wind load and impact load) of major concrete structures containing CRT glass is still limited. In this paper, a dynamic thermo-mechanical analysis test with various frequencies (0.1 Hz–2.0 Hz) and temperatures (−30 °C−30 °C) is undertaken on mortars with different CRT replacement ratios (0, 20%, 40%, 60%, 80%, and 100%). The test results show that the storage modulus (stiffness) of mortar with incorporated CRT glass is lower than that of control mortar in most cases, but the decreasing trend is not proportional to the CRT replacement ratio. However, the presence of CRT glass in the mix has a negligible impact on the frequency dependence of the storage modulus of mortar. The storage modulus of each replacement ratio is nearly constant for all excitation frequencies. The frequency dependence of loss tangent (damping behavior) is significantly improved with CRT glass under 0 °C. This indicates that a frequency dependent damping model is needed when dynamic analysis is conducted on concrete structures with incorporated CRT glass in cold weather.

Extraction of lead from waste CRT funnel glass by generating lead sulfide – An approach for electronic waste management

Waste cathode ray tube (CRT) funnel glass is the key and difficult points in waste electrical and electronic equipment (WEEE) disposal. In this paper, a novel and effective process for the detoxification and reutilization of waste CRT funnel glass was developed by generating lead sulfide precipitate via a high-temperature melting process. The central function in this process was the generation of lead sulfide, which gathered at the bottom of the crucible and was then separated from the slag. Sodium carbonate was used as a flux and reaction agent, and sodium sulfide was used as a precipitating agent. The experimental results revealed that the lead sulfide recovery rate initially increased with an increase in the amount of added sodium carbonate, the amount of sodium sulfide, the temperature, and the holding time and then reached an equilibrium value. The maximum lead sulfide recovery rate was approximately 93%, at the optimum sodium carbonate level, sodium sulfide level, temperature, and holding time of 25%, 8%, 1200°C, and 2h, respectively. The glass slag can be made into sodium and potassium silicate by hydrolysis in an environmental and economical process.

A comparative study on the properties of the mortar with the cathode ray tube funnel glass sand at different treatment methods

With the rapid advances of the electronic industry, the management of the cathode ray tube (CRT) glass waste has become a major environmental problem. In this study, the CRT funnel glass sand untreated with nitric acid (n-TFG) and treated with nitric acid (TFG) were used to replace river sand as fine aggregate for the production of the mortar. The TFG glass sand series mortars exhibit the worse fluidity and fluidity preservation, the shorter setting times, the lower wet density and mechanical properties than those with n-TFG glass sand. The use of TFG glass sand in the mortar also results in the lower drying shrinkage, alkali-silica reaction (ASR) expansion and leaching content of lead than the blended n-TFG glass sand mortars. Moreover, at the drying shrinkage period of 56days, the drying shrinkage values of the mortars with TFG glass sand are within the limit of 0.075%. The mortars prepared by TFG glass sand have a low ASR expansion, at the tested age of 14days, which are below permissible limits (0.10%). The lead leaching of the mortars with TFG glass sand comply with the regulatory limits.

Recycling of incinerated sewage sludge ash and cathode ray tube funnel glass in cement mortars

This study aimed to explore the feasibility of using cement blended with ISSA as cementitious materials in the production of cement mortars using recycled CRT glasses as fine aggregates. For comparison purposes, fly ash (FA) and ground granulated blast furnace slag (GGBS) were also used. Fresh and hardened properties of the cement mortars, as well as potential lead (Pb) leaching were investigated. The experimental results showed that the incorporation of ISSA to replace cement reduced the workability, hardened density and compressive strength but increased the water adsorption, drying shrinkage and flexural strength of the mortars. The influence of the different mineral admixtures on the properties of cement mortars was closely related to their pozzolanic activities and water adsorption abilities. ISSA was superior to FA and GGBS in enhancing the flexural strength and reducing Pb leaching of the mortar samples. It is noteworthy that Pb leaching from the mortar samples prepared with both ISSA and CRT glass was greatly reduced and it complied with the local regulatory limits, and increasing the replacement ratio of cement by ISSA led to a corresponding reduction in the Pb leachate concentrations mainly due to the adsorption and precipitation of Pb by ISSA.

An Innovative Method for the Extraction of Metal from Waste Cathode Ray Tubes through a Mechanochemical Process Using 2-[Bis(carboxymethyl)amino]acetic Acid Chelating Reagent

To minimize electronic waste and reduce the environmental impact of hazardous metals, a new greener approach has been developed for the extraction of lead and barium metals from waste cathode ray tube (CRT) glass. The process steps comprise an initial mechanical activation of CRT funnel glass and then wet ball milling of the funnel glass powder using the metal chelate reagent 2-[bis(carboxymethyl)amino]acetic acid (NTA) and water at room temperature. After the mechanochemical treatment, the desired ≳99 mass % of lead and barium metals contained in the funnel glass powder was extracted as a metal–NTA species and pure nonleaded SiO2 glass material from the funnel glass matrix. The separation was accelerated by the ball-milling atomization and high stability constant of the metal–NTA species. After separation, the maximal amounts of lead and barium ions (∼99 mass %) were obtained as PbSO4 and BaSO4, respectively, with the addition of ferric sulfate. Notably, the developed method does not require heat and doe...

Water-soluble lead in cathode ray tube funnel glass melted in a reductive atmosphere

In the reduction-melting process, lead can be recovered from cathode ray tube funnel glass (PbO=25wt%); however, resulting glass residues still contain approximately 1–2wt% of unrecovered lead. For environmental protection in the residue disposal or recycling, it is important to evaluate the quantities of water-soluble species among the unrecovered lead. This study examined water-soluble lead species generated in the reduction-melting process of the funnel glass and factors determining their generation. In the reduction-melting, metallic lead was generated by reducing lead oxides in the glass, and a part of the metallic lead remained in the glass residue. Such unrecovered metallic lead can dissolve in water depending on its pH level and was regarded as water-soluble lead. When 10g Na2CO3 was added to 20g funnel glass during reduction-melting, the resulting glass contained high concentrations of sodium. In a water leaching of the glass, the obtained leachate was alkalized by the sodium-rich glass (pH=12.7–13.0). The unrecovered metallic lead in the glass was extracted in the alkalized leachate. The quantity of the unrecovered metallic lead (water-soluble lead) in the glass decreased when the melting time, melting temperature, and carbon dosage were controlled during reduction-melting.

Recycled CRT Funnel Glass as Coarse Aggregate and Fine Aggregate in the Radiation Protection Concrete

In recent decades, high-tech electrical equipment has drastically proliferated instead of Cathode Ray Tube (CRT), making CRT funnel glass potential hazardous solid waste. Due to a relatively high level of lead, CRT funnel glass could be used as a potential material for the production of anti-radioactive concrete. In our study the CRT funnel glass , which was separated as aggregate in the concrete, was reduced to 4.75-25 mm (coarse aggregates) and less 4.75 mm (fine aggregates) in the production of anti-radioactive concrete. Mixes containing 0%, 20%, 40% , 60%, 80% and 100% (volume percentage) of CRT funnel glass to replace fine aggregate and coarse aggregate (respectively or simultaneously)) were prepared. The influence of the size, shape and replacement percentage of aggregates on workability, compressive strength and radiation shielding performance were determined. It was found that the replacement of natural aggregate with recycled CRT glass considerably improved the slump and radiation shielding performance but reduced compressive strength. The optimum percentage of waste funnel glass used as fine aggregate and coarse aggregate was 40%. The results clearly showed that the CRT funnel glass performed a significant enhancement in radiation shielding properties.

A Typical e-waste—Cathode Ray Tube Glass: Alkaline Leaching in the Sulfur-Containing Medium

With more and more cathode ray tube (CRT)-based sets reaching their end-of-life or being replaced, how to deal with the CRT glass has become a global concern due to its high lead level. There is a pressing and ongoing need to develop new recycling methods for CRT glass. In this work, the alkaline leaching of CRT funnel glass in the sulfur-containing medium (S and NaS) was probed. The effects of alkaline concentration, S/Pb molar ratio, temperature and leaching time were investigated. The results showed that the recovery rate of both Si and Pb increased with increasing alkaline concentration; however, it decreased again when the concentration was higher than the critical value 6M. The recovery rate of Pb in both media decreased with increasing S/Pb molar ratio. As a comparsion, the recovery rate of Si did not change significantly. The extraction of Si and Pb, especially Si, tightly depended on the temperature. They also increased with extending of time, however, they tended to decrease when the reaction time exceeded 8h. The optimal condition was determined as: alkaline concentration 6M, S/Pb molar ratio 1.0:1, temperature 180°C and leaching time 8h.

Lead recovery and glass microspheres synthesis from waste CRT funnel glasses through carbon thermal reduction enhanced acid leaching process

In this study, a novel process for detoxification and reutilization of waste cathode ray tube (CRT) funnel glass was developed by carbon thermal reduction enhanced acid leaching process. The key to this process is removal of lead from the CRT funnel glass and synchronous preparation of glass microspheres. Carbon powder was used as an isolation agent and a reducing agent. Under the isolation of the carbon powder, the funnel glass powder was sintered into glass microspheres. In thermal reduction, PbO in the funnel glass was first reduced to elemental Pb by carbon monoxide and then located on the surface of glass microspheres which can be removed easily by acid leaching. Experimental results showed that temperature, carbon adding amount and holding time were the major parameters that controlled lead removal rate. The maximum lead removal rate was 94.80% and glass microspheres that measured 0.73–14.74μm were obtained successfully by setting the temperature, carbon adding amount and holding time at 1200°C, 10% and 30min, respectively. The prepared glass microspheres may be used as fillers in polymer materials and abrasive materials, among others. Accordingly, this study proposed a practical and economical process for detoxification and recycling of waste lead-containing glass.

Lead recovery from scrap cathode ray tube funnel glass by hydrothermal sulphidisation.

This research focused on the application of the hydrothermal sulphidisation method to separate lead from scrap cathode ray tube funnel glass. Prior to hydrothermal treatment, the cathode ray tube funnel glass was pretreated by mechanical activation. Under hydrothermal conditions, hydroxyl ions (OH(-)) were generated through an ion exchange reaction between metal ions in mechanically activated funnel glass and water, to accelerate sulphur disproportionation; no additional alkaline compound was needed. Lead contained in funnel glass was converted to lead sulphide with high efficiency. Temperature had a significant effect on the sulphidisation rate of lead in funnel glass, which increased from 25% to 90% as the temperature increased from 100 °C to 300 °C. A sulphidisation rate of 100% was achieved at a duration of 8 h at 300 °C. This process of mechanical activation and hydrothermal sulphidisation is efficient and promising for the treatment of leaded glass.

Removal of lead from cathode ray tube funnel glass by combined thermal treatment and leaching processes

The reduction melting process is useful to recover toxic lead from cathode ray tube funnel glass; however, this process generates SiO2-containing residues that are disposed in landfill sites. To reduce the volume of landfill waste, it is desirable to recycle the SiO2-containing residues. In this study, SiO2 powder was recovered from the residue generated by reduction melting. The funnel glass was treated by a process combining reduction melting at 1000°C and annealing at 700°C to recover a large quantity of lead from the glass. The oxide phase generated by the thermal treatment was subjected to water leaching and acid leaching with 1M hydrochloric acid to wash out unwanted non-SiO2 elements for SiO2 purification. In the water washing, the oxide phase was microparticulated, and porous structures formed on the oxide surfaces. This increased the surface area of the oxide phase, and the unwanted elements were effectively washed out during the subsequent acid leaching. By controlling the acid leaching time and the amount of added acid, porous and amorphous SiO2 (purity >95wt%) was recovered. In the obtained SiO2-concentrated product, unrecovered lead remained at concentrations of 0.25–0.79wt%. When the Na2CO3 dosage in the thermal treatment was increased, the lead removal by acid leaching was enhanced, and the lead concentration in the obtained product decreased to 0.016wt%.

Recycling metals from wastes: a novel application of mechanochemistry.

Recycling metals from wastes is essential to a resource-efficient economy, and increasing attention from researchers has been devoted to this process in recent years, with emphasis on mechanochemistry technology. The mechanochemical method can make technically feasible the recycling of metals from some specific wastes, such as cathode ray tube (CRT) funnel glass and tungsten carbide waste, while significantly improving recycling efficiency. Particle size reduction, specific surface area increase, crystalline structure decomposition and bond breakage have been identified as the main processes occurring during the mechanochemical operations in the studies. The activation energy required decreases and reaction activity increases, after these changes with activation progress. This study presents an overall review of the applications of mechanochemistry to metal recycling from wastes. The reaction mechanisms, equipment used, method procedures, and optimized operating parameters of each case, as well as methods enhancing the activation process are discussed in detail. The issues to be addressed and perspectives on the future development of mechanochemistry applied for metal recycling are also presented.

Lead extraction from cathode ray tube funnel glass melted under different oxidizing conditions

Lead was extracted into hydrochloric acid from cathode ray tube funnel glass melted under reducing atmosphere, oxidizing atmosphere, or a sequential combination of both to mechanistically investigate effects of the melting atmosphere on lead extraction. Melting funnel glass in a reductive atmosphere led to the generation of metallic lead particles that were readily soluble in the acid, increasing the quantity of lead extracted into the acid. Meanwhile, the glass product obtained after melting funnel glass in an oxidative atmosphere exhibited higher corrosion resistance in the acid, and the quantity of lead extracted from the treated glass decreased. However, Na2CO3 addition to the glass during melting hindered the enhancement of corrosion resistance and the immobilization of lead in the acid. X-ray photoelectron spectroscopic analysis of the treated glass samples showed that the positions of the peak or the profiles of the spectra attributed to Pb 4f, Si 2p, and O 1s signals were modified by oxidative melting, an indication that oxidative melting results in structural changes in the SiO2 framework of the glass.

Application of mechanochemistry to metal recovery from second-hand resources: a technical overview.

In the context of huge imbalance between increasing demand for metals and the finiteness of metal resources in nature, recycling metal from second-hand resources, especially e-waste, is of great importance, to embrace the sustainability challenge. Inspired by its hundreds of uses in extractive metallurgy, mechanochemistry has been introduced to recover metals from waste since the 1990s. The mechanochemical recycling process is technically feasible to recover metals from waste in a high yield, such as Pb recovery from cathode ray tube (CRT) funnel glass, Li and Co recovery from lithium-ion batteries, rare earth recovery from fluorescent lamps. In recovery from LCD screens, Cu recovery from waste printed circuit boards and Au, Mo and Ni recovery from waste. Particle size reduction, specific surface area increase, crystalline structure decomposition and bond breakage have been identified as the main changes induced by the mechanochemical processes in the studies. Also, the activation energy required decreases and reaction activity increases, subsequently. This paper presents a technical overview of the applications of mechanochemistry to metal recycling from waste. The current application pattern, reaction mechanisms, equipment used, method procedures, and the future research direction are discussed in detail. This work presents the limitation of current mechanochemical application in metal recovery and gives a perspective of the future development of mechanochemistry as well.

Removal of lead from cathode ray tube funnel glass by generating the sodium silicate

In the disposal of electronic waste, cathode ray tube (CRT) funnel glass is an environmental problem of old television sets. Removal of the lead from CRT funnel glass can prevent its release into the environment and allow its reuse. In this research, we reference the dry progress productive technology of sodium silicate, the waste CRT glass was dealt with sodium silicate frit melted and sodium silicate frit dissolved. Adding a certain amount of Na2CO3 to the waste CRT glass bases on the material composition and content of it, then the specific modulus of sodium silicate frit is obtained by melting progress. The silicon, potassium and sodium compounds of the sodium silicate frit are dissolved under the conditions of high temperature and pressure by using water as solvent, which shows the tendency that different temperature, pressure, liquid-solid ratio and dissolving time have effect on the result of dissolving. At 175°C(0.75MPa), liquid-solid ratio is 1.5:1, the dissolving time is 1h, the dissolution rate of sodium silicate frit is 44.725%. By using sodium sulfide to separate hydrolysis solution and to collect lead compounds in the solution, the recovery rate of lead in dissolving reached 100% and we can get clean sodium silicate and high purity of lead compounds. The method presented in this research can recycle not only the lead but also the sodium, potassium and other inorganic minerals in CRT glass and can obtain the comprehensive utilization of leaded glass.Implications:Waste cathode ray tube (CRT) funnel glass has become a serious environmental problem throughout the world. However, some techniques in the processing of CRT waste have disadvantages such as low lead recovery, low level of comprehensive utilization, technical constraint, economic costs, and other factors, so the actual practical application is still not possible. Therefore, in order to solve lead pollution existing in the waste CRT glass and to solve resource utilization problems, it is necessary to develop a waste CRT process technology that is friendly to environment, cost-saving, and feasible.

Characterization of residue from leached cathode ray tube funnel glass: reutilization as white carbon black

Cathode ray tube (CRT) funnel glass remains an urgent environmental problem and is composed mainly of lead oxide and silicon oxide. In this research, the residue could be obtained from 2 h to 500 rpm activated CRT funnel glass after extracting lead via acid leaching under the conditions of HNO3 concentration 1.0 mol/L, leaching temperature 95 °C and leaching time 1 h. In order to reutilize the residue, its physico-chemical properties were characterized by scanning electron microscopy, Brunauer–Emmett–Teller, thermogravimetric analysis, X-ray diffraction and Fourier transform infrared spectroscopy. The results indicated that the residue was an amorphous superfine powder with approximately 93 wt% silica oxide and specific surface area of more than 170 m2/g. It can be reutilized as white carbon black.

Evaluation of lead recovery efficiency from waste CRT funnel glass by chlorinating volatilization process

The current study was carried out to develop a novel process, namely chloride volatilization procedure for lead recovery from waste cathode ray tube (CRT) funnel glass. In the recovery system, the glass powder was first compressed into cylindrical pellet homogeneously with chlorinating agents, and then subjected to thermal treatment for solid-phase reaction. In this case, lead could be easily released from the silicon oxide network of the glass and it was recovered in the form of PbCl2. It was found that CaCl2 was the most effective chlorinating agent, and the optimum operation temperature, holding time and system pressure were 1000 °C, 2 h, 600±50 Pa, respectively. The evaporated PbCl2 could be easily recovered by a cooling device. The evaporation ratio of lead from waste CRT was 99.1% and the purity of the recovered PbCl2 product was 97.0%. The reaction routes and lead recovery mechanisms of the process were identified. This study provides an efficient and practical process for waste CRT funnel glass detoxification and recycling.

Reduction–melting combined with a Na2CO3 flux recycling process for lead recovery from cathode ray tube funnel glass

With large quantity of flux (Na2CO3), lead can be recovered from the funnel glass of waste cathode-ray tubes via reduction–melting at 1000°C. To reduce flux cost, a technique to recover added flux from the generated oxide phase is also important in order to recycle the flux recovered from the reduction–melting process. In this study, the phase separation of sodium and the crystallization of water-soluble sodium silicates were induced after the reduction–melting process to enhance the leachability of sodium in the oxide phase and to extract the sodium from the phase for the recovery of Na2CO3 as flux. A reductive atmosphere promoted the phase separation and crystallization, and the leachability of sodium from the oxide phase was enhanced. The optimum temperature and treatment time for increasing the leachability were 700°C and 2h, respectively. After treatment, more than 90% of the sodium in the oxide phase was extracted in water. NaHCO3 can be recovered by carbonization of the solution containing sodium ions using carbon dioxide gas, decomposed to Na2CO3 at 50°C and recycled for use in the reduction–melting process.

Use of CRT funnel glass in concrete blocks prepared with different aggregate-to-cement ratios

Managing huge quantities of cathode ray tube (CRT) glass waste has attracted much research interest since the last decade. A recycling process has been developed by The Hong Kong Polytechnic University, to turn hazardous CRT waste glass into valuable resources (e.g. treated funnel glass (TFG)). However, finding a beneficial use for the recycled TFG remains an issue for the local waste management industry. In this study, the use of TFG to replace recycled fine concrete aggregates in concrete blocks prepared with different aggregate-to-cement (A/C) ratios was investigated. The experimental results show that the impermeable nature of TFG made concrete blocks more resistant to water penetration and have lower drying shrinkage. The use of TFG also increased the block density and improved the X-ray radiation–shielding performance. All the blocks demonstrated acceptable compressive strength and alkali-silica reaction behaviour, and a lower A/C ratio could maintain a better alkaline environment and stronger cement matrix structure to stabilize and solidify the TFG in the blocks to prevent lead leaching. On the basis of the findings, the authors concluded that it is feasible to utilize high per cent of TFG in concrete blocks if a proper A/C ratio and appropriate casting method are used.