Comprehensive life cycle assessment of NH2-functionalized magnetic graphene oxide for mercury removal: Carbon emissions and economic evaluation.

Heavy metals contamination critically affects human health and ecosystems, necessitating pioneering approaches to diminish their adverse impacts. Hence, this study synthesized aminated magnetic graphene oxide (mGO-NH2) for the removal of mercury (Hg) from aqueous solutions. Although functionalized GO is an emerging technology at the early stages of development, its synthesis and application require special attention to the eco-environmental assessment. Therefore, the life cycle assessment and life cycle cost of mGO-NH2 were investigated from the cradle-to-gate approach for the removal of 1 kg Hg. The adsorption process was optimized based on pH, Hg concentration, adsorbent dose, and contact time at 6.48, 40 mg/l, 150 mg/l, and 35 min, respectively, resulting in an adsorption capacity of 184.17 mg/g. Human carcinogenic toxicity with a 40.42% contribution was the main environmental impact, relating to electricity (35.76%) and ethylenediamine (31.07%) usage. The endpoint method also revealed the pivotal effect of the mGO-NH2 synthesis on human health (90.52%). The most energy demand was supplied by natural gas and crude oil accounting for 70.8% and 22.1%, respectively. A 99.02% CO2 emission originated from fossil fuels consumption based on the greenhouse gas protocol (GGP). The cost of mGO-NH2 was about $143.7/kg with a net present value of $21064.8 per kg Hg removal for a 20-year lifetime. Considering the significant role of material cost (>70%), the utilization of industrial-grade raw materials is recommended to achieve a low-cost adsorbent. This study demonstrated that besides the appropriate performance of mGO-NH2 for Hg removal, it is essential that further studies evaluate eco-friendly approaches to decrease the adverse impacts of this emerging product.

Assessing the environmental impacts of copper cathode production based on life cycle assessment.

The demand for copper is growing considerably in parallel with economic and technological development. The rate increase in copper consumption in Iran increases pressure on the numerous unexploited mines in southeast Iran and causes the environmental crisis alongside the northern Levar wind in this area. Given this, this study systematically explored the environmental impacts of a one-ton copper cathode processing operation from a cradle-to-gate perspective, using life cycle assessment (LCA). Moreover, the release of greenhouse gases and the energy consumption during the copper cathode production were also assessed. The results indicated that sulfuric acid use in the smelting and extraction stages, metal leaching from tailings, and CO2 dominated more than 50% of contributions to freshwater and marine ecotoxicity, human toxicity, and global warming. The energy analysis revealed 88.92% of crude oil use especially for the electrowinning stage, which should be promoted technologically. For global warming, the indirect CO2 emission from electricity consumption using fossil fuels was the main contributor (94.56%). Therefore, shifting from conventional energy systems to renewable energy systems could alleviate the overall environmental impact. For a 0.57-ton sulfuric acid effluent per one ton of copper cathode production, its treatment and reuse in the process is recommended. Summing up, the results of this study provide the environmental hot spots for copper cathode production for further investigation. Integr Environ Assess Manag 2023;00:1-11. © 2023 SETAC.

High efficient Hg (II) and TNP removal by NH2 grafted magnetic graphene oxide synthesized from Typha latifolia.

The present study for the first time manifests the outstanding potential of amine grafted magnetic graphene oxide (m-GO-NH2) synthesized from Typha latifolia stems for mercury (Hg (II)) and 2,4,6-trinitrophenol (TNP) removal. The adsorption performance of m-GO-NH2 was apprized by considering the impact of the contact time (0-120 min), pH (2-9), adsorbent dose (5-40 mg), and adsorbate concentration (10-50 mg/L). The maximum Hg (II) and TNP removals (∼ 100%) were obtained using 30 mg adsorbent dose in 90 and 75 min, respectively. The best performance of m-GO-NH2 was observed at pH of 7, 20 mg/L Hg (II), and pH of 2, 30 mg/L TNP. According to the Brunauer-Emmett-Teller (BET) analysis, the surface area of GO was 34.81 m2/g and the simultaneous micro and mesoporosity was observed. Regarding the thermodynamic studies, the adsorption procedure was spontaneous and endothermic for Hg (II) followed Redlich-Peterson (R-P) and Freundlich isotherm equations while it was exothermic for TNP, well fitted with Langmuir and R-P isotherms. Kinetic data also indicated a good correlation with pseudo-second-order model. The highest adsorption capacity was estimated as 107.33 and 105.2 mg/g for Hg (II) and TNP, respectively. Accordingly, the proposed m-GO-NH2 can be a promising adsorbent for the elimination of metal and organic contaminants.