Hydrometallurgical Recycling Process for Mobile Phone Printed Circuit Boards Using Ozone

Two-Stage Leaching of PCBs Using Sulfuric and Nitric Acid with the Addition of Hydrogen Peroxide and Ozone

The paper presents the possibility of recovering metals from printed circuit boards (PCBs) of spent mobile phones using the hydrometallurgical method. Two-stage leaching of Cu(II), Fe(III), Sn(IV), Zn(II), Ni(II) and Pb(II) with H2SO4 (2 and 5 M) and HNO3 (2 M) with the addition of H2O2 (10 and 30%) and O3 (9 or 15 g/h) was conducted at various process conditions (temperature-313, 333 and 353 K, time-60, 120, 240, 300 min, type and concentration of leaching agent, type and concentration of oxidant, solid-liquid ratio (S/L)), allowing for a high or total metals leaching rate. The use of two leaching stages allows for the preservation of selectivity, separation and recovery of metals: in the first stage of Fe(III), Sn(IV) and in the second stage of the remaining tested metal ions, i.e., Cu(II), Zn(II), Ni(II) and Pb(II). Removing Fe from the tested PCBs' material at the beginning of the process eliminates the need to use magnetic methods, the purpose of which is to separate magnetic metal particles (ferrous) from non-magnetic (non-ferrous) particles; these procedures involve high operating costs. Since the leaching of Cu(II) ions with sulfuric(VI) acid practically does not occur (less than 1%), this allows for almost complete transfer of these ions into the solution in the second stage of leaching. Moreover, to speed up the process and not generate too many waste solutions, oxidants in the form of hydrogen peroxide and ozone were used. The best degree of leaching of all tested metal ions was obtained when 2 M sulfuric(VI) acid at 353 K was used in the 1st research stage, and 2 M nitric(V) acid and 9 g/h O3 at 298 K in the 2nd stage of leaching, which allowed it to be totally leached 100% of Fe(III), Cu(II), Sn(IV), Zn(II), Ni(II) and 90% Pb(II).

Composition and recycling of smartphones: A mini-review on gaps and opportunities

After more than a decade since smartphones became consolidated in the market, many recycling solutions have been proposed to deal with them. To continue developing useful solutions and enable adjustment of routes, this mini-review aims to analyse the current research scenario, presenting relevant gaps, trends and opportunities. From a structured searching and screening procedure, a vast source of data was arranged and is available to extract useful information (43 studies on composition and 93 studies on recycling). The study provides discussions about the history of smartphone development, constituent materials and recycling methods for different components, comparisons between feature phones and smartphones and others. Among some conclusions, the authors highlight the lack of studies on pre-extractive methods, green chemistry, recovery of critical and precious metals, determination of priority materials for recovery and solutions for entire devices. In the end, a list containing six research gaps for composition studies and seven research gaps for recycling studies is provided and may be seen as opportunities for future research.

Novel applications of vacuum distillation for heavy metals removal from wastewater, copper nitrate hydroxide recovery, and copper sulfide impregnated activated carbon synthesis for gaseous mercury adsorption

Hydrometallurgical processing of electronic waste produces copper (Cu)-containing wastewater. Recycling of Cu is thus crucial, as it reduces the Cu impact on the environment, and increases Cu sustainability in industry. Vacuum distillation provides excellent performance in both metals removal from aqueous solution, metal recovery, and metal impregnation to porous material. Thus, this work aimed to both utilize a vacuum distillation to remove heavy metals (Cu, Na, Ni, Zn and Fe) and recover copper nitrate hydroxide (Cu₂NO₃(OH)₃) from Cu-containing wastewater in industrial applications (e.g., mordant agent in dyeing and pigment for glass), as well as prepare copper sulfide (CuS) impregnated activated carbon for mercury (Hg⁰) adsorption. The experimental results indicated a vacuum distillation metals removal efficiency of over 99.99 % at 60 °C and -72 cm Hg. Additionally, the copper nitrate hydroxide (Cu₂NO₃(OH)₃) crystalline solid derived from the vacuum distillation process achieved 77 % purity, and the copper sulfide impregnated activated carbon (CuSAC) adsorbents were prepared by adding activated carbon (AC) during the vacuum distillation process. In adsorption tests, 50 % CuSAC exhibited the greatest gaseous mercury (Hg⁰) adsorption performance, and it was noted that a high adsorption temperature of 175 °C negatively impacted Hg⁰ adsorption of 50 % CuSAC due to mercury sulfide (HgS) decomposition. Furthermore, in a simulated flue gas (SFG) environment, Hg⁰ capture by CuSAC was shown to be slightly obstructed. In addition, mercury temperature-programmed desorption (Hg-TPD) identified that HgS was the dominant species among adsorbed Hg species of Hg-laden 50 % CuSAC, indicating that Hg⁰ capture of CuSAC was mainly facilitated by sulfur active sites. As such, the vacuum distillation technique proved to efficiently remove metals and leads to successful preparation of adsorbent for Hg. Therefore, the process is an effective treatment method for Cu-containing wastewater, and can be practically applied to capture or recycle Cu in the industry in the future.

Leaching of Copper Contained in Waste Printed Circuit Boards, Using the Thiosulfate-Oxygen System: A Kinetic Approach

The present work is related to the treatment of crushed waste of printed circuit boards (WPCBs) from electrical and electronic devices (WEEE), carrying out the recovery of copper in solution. In the first stage, the studied material was characterized by AAS, SEM-EDS, and XRD. The results revealed significantly high amounts of copper (744.42 mg/g), compared with the rest of the metals present in the sample, mainly iron and zinc. In the second stage of the work, alkali dynamic leaching experiments were carried out in the S2O3−2− O2 medium, evaluating important kinetic variables in order to verify the controlling step of the system and adjust the data to a kinetic model. According to the results obtained from the various experimental tests executed, it was found that in the studied system of S2O3−2− O2, the leaching of copper was preferably adjusted to the model of spherical particles with a shrinking core finding a mixed chemical−diffusive control, with values of Ea = 25.78 kJ/mol and n = 0.22 (for the leaching reagent), indicating that the reaction was controlled by the oxygen transport to the solid−liquid interface and also by the chemical reaction in the surface of particles, obtaining up to 99.82% copper in solution.

Recent Developments in Steelmaking Industry and Potential Alkali Activated Based Steel Waste: A Comprehensive Review

The steel industry is responsible for one-third of all global industrial CO2 emissions, putting pressure on the industry to shift forward towards more environmentally friendly production methods. The metallurgical industry is under enormous pressure to reduce CO2 emissions as a result of growing environmental concerns about global warming. The reduction in CO2 emissions is normally fulfilled by recycling steel waste into alkali-activated cement. Numerous types of steel waste have been produced via three main production routes, including blast furnace, electric arc furnace, and basic oxygen furnace. To date, all of the steel waste has been incorporated into alkali activation system to enhance the properties. This review focuses on the current developments over the last ten years in the steelmaking industry. This work also summarizes the utilization of steel waste for improving cement properties through an alkali activation system. Finally, this work presents some future research opportunities with regard to the potential of steel waste to be utilized as an alkali-activated material.