Gold recovery from waste printed circuit boards of mobile phones by using microwave pyrolysis and hydrometallurgical methods

Recycling of waste printed circuit boards (PCBs) has attracted increasing attention because of its high annually produced amount and high content of gold. In this study, gold recovery from waste PCBs was carried out by using the processes including microwave pyrolysis, acid leaching, solvent extraction and oxidative precipitation. The leaching efficiency of copper was approximately 95% when using a lixiviant composed of sulfuric acid and hydrogen peroxide, and the leaching efficiencies of gold were approximately 59, 95 and 95% by using thiourea, thiosulfate and aqua regia, respectively. The gold ions contained in the leachate previously produced by the leaching processes were not satisfactorily extracted by using organic solvents including di-(2-ethylhexyl)phosphoric acid, tributyl phosphate, dibutyl carbitol and trioctylamine, so the leachate was decided to bypass solvent extraction and directly apply to the oxidative precipitation process. By using the oxidants of hydrogen peroxide and perchloric acid, the precipitation efficiencies of gold were approximately 95 and 99%, and the final recovery rates were approximately 90 and 93%, respectively. The high recovery rates of gold can be attributable to the use of microwave pyrolysis that prevents the loss of gold caused by shredding and grinding processes. In addition, perchloric acid can provide higher selectivity for gold recovery than hydrogen peroxide. The maximum processing capacity of microwave pyrolysis of waste PCBs would be approximately 1.23 kg. The gold recovered from 1 t of waste PCBs can be sold for approximately USD 10,000, and thus the return on investment can be as high as approximately 1400%.

The Environmentally Friendly Possibility of Using Recycled Plastic from Electrical Waste to Rainwater Detention

In view of the dynamic development of electrical and electronic equipment and the reduction of its lifetime, the share of electronic equipment that has become waste has risen. In proportion to this situation, there is a constant improvement in separating industrial methods aimed at removing hazardous components of electrical waste (PCBs containing condensers, mercury switches or asbestos insulation). Another commodity, and economically more interesting, is the obtaining of the utility component of the waste iron and non-ferrous metals. After the separation of the interesting components what remains is a heterogeneous mixture of plastic pulp, which is usually landfilled or incinerated in the waste incinerator. This leads to the loss of valuable material, which could be further exploited. The paper deals with the issue of the disposal of plastics from electrical waste and its subsequent use as plastic pulp, which can be used to fill the rainwater detention reservoir.

Recycling of Printed Circuit Boards by Direct Molding Technology

The recovery and reuse of printed circuit boards (PCBs) is becoming crucial in the management of electronic waste that is undergoing an exponential increase. In this study, a simple and eco-friendly process for recycling waste PCBs is discussed. In particular, composite panels were produced by reusing 100% of waste PCBs without the addition of any additive or virgin material. After a two-step grinding process, ground PCB was used to mold panels by direct molding which is pure compression molding without material sorting. Results were very promising in terms of process feasibility and part performances. Molded samples had density about 1.45 g/cm3, flexural modulus and flexural about 3 GPa and 16 MPa, respectively. A smooth surface with low friction coefficient was obtained for the recycled panels. The study shows that despite the presence of metal and other non-metal non-organic fractions, waste PCBs can be re-processed in profitable and environmentally conscious way without the addition of any bonding agent or additive. The recycling technology can be extended to the reuse of the non-metallic fraction only, after separation and recovery of metals.

Decomposition of LCD screen inverter by pyrolysis

PCBs (Printed Circuit Boards) are important parts of electronic equipment and their use increases with technology development. Recycling of waste PCBs is challenging due to their complex structure and receives wide concerns as the amount of this type of waste is growing rapidly. In the article, the experiment of pyrolysis carried out with electronic waste sample was presented. The material employed in the present work was inverter of the LCD screen that it the example of the multilayer PCB. The correlation between pyrolysis temperature and gas emission from the system, which is associated with epoxy resin decomposition, is presented in the article.