The study of geopolymers has become an interesting concern for many scientists, especially in the infrastructure sector, due to having inherently environmentally friendly properties and fewer energy requirements in production processes. Geopolymer attracts many scientists to develop practical synthesis methods, useful in industrial-scale applications as supplementary material for concrete. This study investigates the geopolymerization of fly ash and geothermal silica-based dry activator. The dry activator was synthesized between NaOH and silica geothermal sludge through the calcination process. Then, the geopolymer mortar was produced by mixing the fly ash and dry activator with a 4:1 (wt./wt.) ratio. After mixing homogeneously and forming a paste, the casted paste moved on to the drying process, with temperature variations of 30, 60, and 90 °C and curing times of 1, 3, 5, 7, 14, 21, 28 days. The compressive strength test was carried out at each curing time to determine the geopolymer’s strength evolution and simulate the reaction’s kinetics. In addition, ATR-FTIR spectroscopy was also used to observe aluminosilicate bonds’ formation. The higher the temperature, the higher the compressive strength value, reaching 22.7 MPa at 90 °C. A Third-order model was found to have the highest R² value of 0.92, with the collision frequency and activation energy values of 1.1171 day⁻¹ and 3.8336 kJ/mol, respectively. The utilization of coal fly ash and silica geothermal sludge as a dry activator is, indeed, an approach to realize the circular economy in electrical power generations.

There is a shift from internal combustion engines to electric vehicles (EVs), with the primary goal of reducing CO₂ emissions from road transport. Battery technology is at the heart of this transition as it is vital to hybrid and fully electric vehicles’ performance, affordability, and reliability. However, it is not abundant in nature. Lithium has many uses, one of which is heat transfer applications; synthesized as an alloying agent for batteries, glass, and ceramics, it therefore has a high demand on the global market. Lithium can be attained by extraction from other natural resources in igneous rocks, in the waters of mineral springs, and geothermal brine. During the research, geothermal brine was used because, from the technological point of view, geothermal brine contains higher lithium content than other resources such as seawater. The nanofiltration separation process was operated using various solutions of pH 5, 7, and 10 at high pressures. The varying pressures are 11, 13, and 15 bar. The nanofiltration method was used as the separation process. High pressure of inert nitrogen gas was used to supply the driving force to separate lithium from other ions and elements in the sample. The research results supported the selected parameters where higher pressure and pH provided more significant lithium recovery but were limited by concentration polarization. The optimal operating conditions for lithium recovery in this research were obtained at a pH of 10 under a pressure of 15 bar, with the highest lithium recovery reaching more than 75%.

In the current study, a leaching of manganese from Indonesian manganese ores using citric acid as leaching reagent without the addition of reducing agent was investigated. Citric acid was being used as a leaching reagent and reducing agent at same time due to its reducing power. Several leaching parameters were investigated to obtain the optimum condition of citric acid leaching of manganese from those manganese ores. Low grade manganese ores from two mining areas in Indonesia contained 36.77% Mn (WK ore) and 12.5% (TG ore) with different mineral types can be leached using citric acid as leaching reagent without addition of reducing agent. The optimum manganese recovery was obtained at around 76% and 69% respectively for WK ore and TG ore with citric acid of 1M, 5% of pulp density, 150 rpm of shaker speed, 30oC of leaching temperature, 1 hour of leaching period, and <75 µm of ore particle size. This condition was also selective for iron recovery leaching. This experiment proves that citric acid has a dual-synergistic effect as an effective leaching reagent and reducing agent at the same time for manganese leaching from manganese ores.

Ion-imprinted polymers (IIPs) are advanced adsorbents featuring selective recognition cavities for targeted metal ion capture, offering a promising route to high-efficiency separation in extractive metallurgy. In the present work, the evolution, design principles, synthesis strategies, separation mechanisms, and practical applicability of IIPs for metal recovery from complex aqueous matrices are overviewed. Key material components, including functional monomers, crosslinkers, template ions, initiators, solvents, and support materials, are discussed in relation to adsorption capacity, selectivity, kinetics, stability, and recyclability. Major preparation routes, such as surface imprinting, bulk polymerization, in situ polymerization, and sol–gel methods, are critically compared to clarify their advantages and limitations. Recent applications for base metals, precious metals, and rare-earth elements demonstrate that IIPs can achieve high specificity and rapid equilibrium under optimized conditions. However, their translation from simulated solutions to real leachates remains constrained by interfering ions, organic contaminants, mass transfer resistance, incomplete template removal, and matrix complexity. Mitigation strategies, including sample pretreatment, improved polymer architecture, and hybrid supports, are therefore emphasized. Additionally, chemometric modelling, machine learning, or artificial intelligence-assisted design may be implemented to advance the prospects of IIPs in industry. Conclusively, IIPs represent a strong separation platform, yet industrial deployment requires robust validation with real feed streams and scalable regeneration protocols during column operation, as well as under chemically aggressive conditions at scale.

In this study, sugarcane bagasse was used as a reducing agent in manganese leaching from manganese ore from Way Kanan, Lampung under acidic conditions using sulfuric acid as a leaching reagent. Bagasse is an agricultural waste from the cane sugar manufacturing industry which is commonly found in Lampung Province. This agricultural waste has the potential to become a reducing agent in manganese leaching because it contains carbon in the form of cellulose and sugar. The optimization of the leaching conditions has been investigated with the parameters of H2SO4 concentration, temperature, and pulp density. The highest manganese leaching recovery was obtained under the following optimized conditions: 1 M H2SO4 concentration, 14 g sugarcane bagasse/20 g MnO2, 50 g/L pulp density, 80 °C leaching temperature, 200 rpm stirring rate, and 4 hours of reaction time. The present process therefore deals with achieving the effective recovery of value-added products from low-grade manganese ore using agriculture waste as reducing agent.

A study has been done to investigate and optimize the recovery of nickel from nickel-containing spent catalyst through sulfuric acid (1 - 2 mol/L) atmospheric leaching in different operation conditions. From the leaching experiments, it was possible to extract 77.95% nickel under the conditions of 2 mol/L H2SO4, reaction time of 5 h, 5% pulp density, and temperature of 80°C. In the next step Ni was selectively precipitated from a sulfuric acid-leached solution using 1 mol/L oxalic acid. The nickel content in the product was 97.29% Ni. Based on the study, sulfuric acid was found to be a suitable leaching agent to extract Ni from the nickel-containing spent catalyst. The study also indicated the effective extraction and recovery of nickel which was well supported by characterization studies using XRD technique.