Simulating the Influence of Supporting Electrolyte Concentration on Copper Electrodeposition in Microvias

Robust, void-free Cu electrodeposition in high-aspect ratio features relies on careful tuning of electrolyte additives, concentrations, and electrochemical parameters for a given feature dimension or wafer pattern. Typically, Cu electrodeposition in electronics manufacturing of microscale or larger features (i.e., microvias, through-holes, and high-density interconnects) employs a CuSO4 – H2SO4 electrolyte containing millimolar levels of chloride and, at a minimum, micromolar levels of a polyether suppressor. Research and optimization efforts have largely focused on the relationship between electrolyte additives and growth morphology, with less attention given to the impact of supporting electrolyte. Accordingly, a computational study exploring the influence of supporting electrolyte on Cu electrodeposition in microvias is presented herein. The model builds upon prior experimental and computational research on localized Cu deposition by incorporating the full charge conservation equation with electroneutrality to describe potential variation in the presence of ionic gradients. In accord with experimental observations, simulations predict enhanced current localization to the microvia bottom as H2SO4 concentration is decreased. This phenomenon derives from enhanced electromigration within recessed features that accompanies the decrease of conductivity with local metal ion depletion. This beneficial aspect of low acid electrolytes is also impacted by feature density, CuSO4 concentration, and the extent of convection.

Hydrometallurgical Recycling of Copper Anode Furnace Dust for a Complete Recovery of Metal Values

Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a laboratory scale. The optimum condition for leaching of zinc from dust was identified to be an ambient leaching temperature, a liquid/solid ratio of 10 and H2SO4 concentration of 1 mol/L. A maximum of 98.85% of zinc was leached under the optimum experimental conditions. In the leaching step, 99.7% of lead in the form of insoluble PbSO4 was separated from the other leached metals. Solution refining was done by combination of pH adjustment and zinc powder cementation. Tin was precipitated from solution by pH adjustment to 3. Iron was precipitated out of solution after pH adjustment to 4 with efficiency 98.54%. Copper was selectively cemented out of solution (99.96%) by zinc powder. Zinc was precipitated out of solution by addition of Na2CO3 with efficiency of 97.31%. ZnO as final product was obtained by calcination of zinc carbonates.

Comparative Study on Refractory Gold Concentrate Kinetics and Mechanisms by Pilot Scale Batch and Continuous Bio-Oxidation

Most studies conducted have focused on the pulp density, Fe3+ concentration and sulfuric acid concentration, etc., of bio-oxidation, and few have reported on the influence of different bio-oxidation methods on kinetics. In this study, a comparative investigation on refractory gold concentrate by batch and continuous bio-oxidation was conducted, with the purpose of revealing the kinetics influence. The results showed that improving the removal rates of the gold-bearing pyrite (FeS2) and arsenopyrite (FeAsS) yielded the best results for increasing gold recovery. The removal rates of S, Fe and relative gold recovery linearly increased when compared to the second-order equation increase of the As removal rate in both batch and continuous bio-oxidation processes. The removal kinetics of S and Fe by continuous bio-oxidation was 12.02% and 12.17% per 24 h day, approximately 86.64% and 51.18% higher than batch bio-oxidation, respectively. The higher removal kinetics of continuous bio-oxidation resulted from a stepwise increase in microbe growth, a larger population and higher dissolved Fe3+ and H2SO4 concentration compared to a linear increase by batch bio-oxidation. The cyanidation gold recovery was as high as 94.71% after seven days of continuous bio-oxidation, with the gold concentrate sulfur removal rates of 83.83%; similar results will be achieved after 13 days by batch bio-oxidation. The 16sRNA sequencing showed seven more microbe cultures in the initial residue than Acid Mine Drainage (AMD) at genus level. The quantitative real-time Polymerase Chain Reaction (PCR) test showed the four main functional average microbe populations of Acidithiobacillus, Leptospirillum, Ferroplasma and Sulfobacillus in continuous bio-oxidation residue as 1.08 × 103 higher than in solution. The multi-microbes used in this study have higher bio-oxidation activity and performance in a highly acidic environment since some archaea co-exist and co-contribute.

The Utilization of Lapindo Mud Waste for Aluminium Sulfate Production

The Lapindo mudflow disaster in East Java Province, or also known as LUSI (LUmpur “mud”-SIdoarjo) has become spectacular longest ongoing disaster in recent memory since 2006. The utilization of volcanic Lapindo mud could be the promising solution to prevent further environmental damage. The chemical composition of Lapindo mud contained of 44.1% SiO2, 23.7% Fe2O3, 13% Al2O3, 7.02% CaO, 5.35% MoO3, 2.53% K2O, 1.84% TiO2 and 0.7% Na2O. Aluminium sulfate (Al2(SO4)3) or “alum” have been widely used as coagulation compound in water treatment, paper and textiles industry. Aluminium sulfate can be synthesized from aluminium oxide (Al2O3) from Lapindo mud with acidic solutions (H2SO4). The aim of this work was to synthesize aluminum sulfate from Lapindo mud by using extraction process. The impact of H2SO4 concentration and heating time to the production of aluminium sulfate have been investigated. The results showed that the aluminium sulfate can be synthesized from Lapindo mud by using H2SO4. Based on XRF analysis, the variation of heating time and H2SO4 concentration affect the aluminium sulfate conversion. The increasing of heating time and H2SO4 concentration directly enhance the conversion until reach the optimum condition. The optimum condition for aluminium sulfate synthesis from Lapindo mud (75.78% conversion) was found to be 90 min for heating time with H2SO4 concentration of 80%

Modelling the Effect of Solution Composition and Temperature on the Conductivity of Zinc Electrowinning Electrolytes

Zinc electrowinning is an energy-intensive step of hydrometallurgical zinc production in which ohmic drop contributes the second highest overpotential in the process. As the ohmic drop is a result of electrolyte conductivity, three conductivity models (Aalto-I, Aalto-II and Aalto-III) were formulated in this study based on the synthetic industrial electrolyte conditions of Zn (50–70 g/dm3), H2SO4 (150–200 g/dm3), Mn (0–8 g/dm3), Mg (0–4 g/dm3), and temperature, T (30–40 °C). These studies indicate that electrolyte conductivity increases with temperature and H2SO4 concentration, whereas metal ions have negative effects on conductivity. In addition, the interaction effects of temperature and the concentrations of metal ions on solution conductivity were tested by comparing the performance of the linear model (Aalto-I) and interrelated models (Aalto-II and Aalto-III) to determine their significance in the electrowinning process. Statistical analysis shows that Aalto-I has the highest accuracy of all the models developed and investigated in this study. From the industrial validation, Aalto-I also demonstrates a high level of correlation in comparison to the other models presented in this study. Further comparison of model Aalto-I with the existing published models from previous studies shows that model Aalto-I substantially improves the accuracy of the zinc conductivity empirical model.

Characterization of Methyl Ester Sulfonate (MES) from Mahagony (Swietenia macrophylla King) with Variations in H2SO4 Concentration and Sulfonation Duration

Methyl ester sulfonate derived from mahogany (<em>Swietenia macrophylla</em> K.) oil has been characterized. The research began by synthesizing mahogany methyl ester (ME) in 4 stages: pressing, degumming, esterification, and transesterification. The next process was synthesizing methyl ester sulfonate (MES) also in four stages: sulfonation, bleaching, neutralization, and drying. The reactant for MES synthesis in this study was H₂SO₄ with a mole ratio of 1:6 and variations in the concentration of H₂SO₄ (70%, 75%, 80%, 85%, and 90%) as well as variations in the duration of sulfonation (45, 60, 75, 70, and 105 minutes) to determine the characteristics of the synthesized MES including density, acid number, and emulsion stability. The effect of the combination of treatment variations was analyzed using the two-way ANOVA test and the least significant difference (LSD) test. This research showed that MES from mahogany seed oil from a combination of variations in treatment has a density ranging from 0.91 to 0.97 g/mL where the LSD test at α = 0.05 produces three different MES density groups due to variations in the concentration of H₂SO₄ namely A (70 % and 75%), B (80% and 85%), and C (90%). The resulting MES acid numbers ranged from 4.69 ‒ 17.74 mgKOH/g sample with three different groups of MES acid numbers due to variations in the concentration of H₂SO₄, namely A (85 and 90%), B (75% and 80%), and C (70%). The stability of mahogany oil-based MES emulsion ranged from 0.000 ‒ 0.975 and two different MES emulsion stability groups were obtained due to variations in the concentration of H₂SO₄, namely A (80% and 85%) and B (70%, 75%, and 90%). FTIR spectrophotometer showed the presence of S=O groups at wavenumber 1172 cm^-1 and S‒O groups at wavenumbers 972.12 cm^-1 and 879.54 cm^-1 proved that MES was successfully synthesized.

The effect of temperature and H2SO4 concentration and soaking time on breaking dormancy of sengon seed (Falcataria moluccana (Miq.) Barneby & J.W. Grimes)

Sengon (Falcataria moluccana (Miq.) Barneby & J.W. Grimes) is a Leguminoceae plant that is useful as material for making panel wood, furniture wood and trees that can rehabilitate critical land. Sengon seeds experience a period of dormancy and need to be managed. The purpose of this study is to determine the effect of temperature 600C and 50% H2SO4 concentration and soaking time on sengon seed germination. A complete randomized design (CRD) with two factors were used as research design. The first factor was the air temperature treatment of kontrol (A1), 60o C (A2), 50% H2SO4 (A3) and which consisted of 3 levels of treatment. The second factor was soaking time (T); T1: 35 minutes, T2: 8 hours. The results showed that the best combination of treatment and immersion time for all germination parameters of sengon seed is soaking seed at 60o C water for 8 hours Key words: Temperature water, H2SO4, Paraserianthes falcataria, germination

Recovery of Pure Pd(II) from Spent Electroplating Solutions by Solvent Extraction with Ionic Liquids from Sulfuric Acid Leaching Solution of Cemented Pd

Palladium (Pd) electroplating is widely practiced in the manufacture of advanced electronic devices. The Pd(II) present in spent electroplating solutions is treated by cementation with zinc (Zn) metal powder. In order to recover pure Pd from the cemented Pd, a process that consisted of leaching followed by solvent extraction was investigated. For this purpose, solvent extraction experiments using synthesized ionic liquids (ILs) with organic and inorganic anions were performed to find separation conditions at which selective extraction of Pd(II) over Zn(II) from synthetic H2SO4 leaching solutions is possible. The concentration of sulfuric acid was varied from 0.5 to 9 M. The complete separation of Pd(II) over Zn(II) by ILs such as ALi–CY301 (N-methyl-N,N,N-trioctylammonium bis(2,4,4-trimethylpentyl) dithiophosphinic), ALi–SCN (N-methyl-N,N,N-trioctylammonium thiocyanate), ALi–I (N-methyl-N,N,N-trioctylammonium iodide) and ALi–Br (N-methyl-N,N,N-trioctylammonium bromide) depends on H2SO4 concentration, while ALi–LIX63 (N-methyl-N,N,N-trioctylammonium 5,8-diethyl-7-hydroxydodecane-6-oxime) and ALi–LIX84 (N-methyl-N,N,N-trioctylammonium 2-hydroxy-5-nonylacetophenone oxime) can completely separate Pd(II) irrespective of H2SO4 concentration. Additionally, the mixture of HCl and thiourea, aqua regia solution, NH3 solution and the mixture of NH4Cl and NH3 are powerful stripping agents for Pd(II) from the loaded ALi–LIX63/ALi–LIX84, ALi–CY301, ALi–Br/ALi–I and ALi–SCN, respectively. However, application of the separation conditions to the real 5 M sulfuric acid leaching solutions of cemented Pd indicated that it was difficult to separate the two ions by extraction with ALi–LIX63 and ALi–LIX84. Use of NaClO as an oxidizing agent during the sulfuric acid leaching of real cemented Pd resulted in an enhancement of Zn(II) extraction by ALi–LIX63 and ALi–LIX84. Therefore, removal of chloride ions from the sulfuric acid leaching solutions is necessary to apply the separation conditions obtained from synthetic sulfuric acid leaching solutions.

Sulfuric acid–amine nucleation in urban Beijing

New particle formation (NPF) is one of the major sources of atmospheric ultrafine particles. Due to the high aerosol and trace gas concentrations, the mechanism and governing factors for NPF in the polluted atmospheric boundary layer may be quite different from those in clean environments, which is however less understood. Herein, based on long-term atmospheric measurements from January 2018 to March 2019 in Beijing, the nucleation mechanism and the influences of H2SO4 concentration, amine concentrations, and aerosol concentration on NPF are quantified. The collision of H2SO4–amine clusters is found to be the dominating mechanism to initialize NPF in urban Beijing. The coagulation scavenging due to the high aerosol concentration is a governing factor as it limits the concentration of H2SO4–amine clusters and new particle formation rates. The formation of H2SO4–amine clusters in Beijing is sometimes limited by low amine concentrations. Summarizing the synergistic effects of H2SO4 concentration, amine concentrations, and aerosol concentration, we elucidate the governing factors for H2SO4–amine nucleation for various conditions.

Effects of Sugars and Degradation Products Derived from Lignocellulosic Biomass on Maleic Acid Production

In this study, maleic acid was produced from xylose contained in a hydrolysate generated by oxalic acid pretreatment of yellow poplar (Liriodendron tulipifera), and the factors that influenced maleic acid production were evaluated. Furfural was obtained from the hydrolysate using H2SO4 as a catalyst, depending on combined severity factors (CSFs). Furfural production increased as the H2SO4 concentration increased. Furfural yield (46.70%), xylose conversion (70.95%), and xylo–oligomer conversion (75.47%) from the hydrolysate were high at CSF 1.92 with 1.64% H2SO4. However, the furfural concentration was slightly increased at 1.64% H2SO4 to 7.10 g/L at CSF 1.89, compared with that at CSF 1.92. Maleic acid was produced from the hydrolysate (CSF 1.92 and 1.64% H2SO4) at a yield of 91.44%. Maleic acid production was slightly better when formic acid and acetic acid were included in the hydrolysate than when furfural was included alone (79.94% vs. 78.82%). Based on the results, the xylose obtained from yellow poplar can be proposed as a new substitute for fossil fuel-derived raw materials.