The large-scale production of high-quality graphene is the major focus of scientists and engineers recently. However, its massive manufacturing routes from its precursor graphene oxide (GO) are involved in the production of toxic gasses and consist of hazardous explosive steps that severely hurt and threaten ecological balance and human health. Therefore, in this study, we investigated the green, effective, and economical approach for the synthesis of graphene by using Vernonia amygdalina (VA) plant leaf extracts for the effective and efficient reduction of GO. The nonexplosive two-step synthesis of GO in a short period of time in the absence of an ice bath was used in this study. The appropriate solvent for the extraction of VA for the green synthesis of graphene was methanol, and the reducing and capping agent in the plant extract was identified to be terpenoids and polyphenols. The graphene/rGO obtained this way was characterized by UV-VIS, XRD, FTIR, SEM, HR-TEM, and EDAX that confirmed the successful reduction of GO to graphene under the hydrothermal process. The HR-TEM images showed the development of few layers of graphene. The FTIR result also shows the complete reduction of GO. Hence, methanol extracted VA leaves consisted of the most appropriate compounds for reducing and capping agent in the green synthesis and could be the preferred method for the large-scale production of graphene-based materials.

In most African rural communities, ground water is the primary source of drinking water. Fluoride is a harmful substance found in ground water that causes serious health problems. The only answer to the fresh and clean water crisis is water treatment. Sustainable, cost-effective and efficient membrane filtration technologies are becoming progressively vital to solve the scarcity. Owing to their unique tunable physico-chemical properties, carbon nanotubes (CNTs) were used in water treatment. This paper thoroughly reviews the health effects of consuming excess fluoride ions. The recent progress on the synthesis of CNT was also highlighted. A special emphasis was given to green synthetic routes for its preparation. Green catalysts provide defined size and morphology than conventional materials and also prevent metal leaching. The effects of incorporation of CNTs as filler in the matrix have been discussed in detail. The large-scale production of CNTs and their growth mechanisms; for water purification purposes are explored. It has been observed that CNTs have got an excellent filtration performance of fluoride, low biofouling activities and high water flux capacity. Besides, this review attempt to provide a clue for the functionalized CNTs based membranes as potential solutions in water purifications of fluoride ions in the future. GRAPHICAL ABSTRACT

The deterioration of the quality of groundwater by fluoride is the cause of shortage of drinking water supply in the rift valley region. Most people living in the rural areas are using groundwater as the source of their potable water; however, it is contaminated with high concentrations of fluoride ion above the permissible level. Hence, this study was designed to investigate the adsorption of fluoride from groundwater by graphene oxide (GO) under specific conditions, such as: agitation rate of 120 rpm, contact time of 90 minutes, adsorbent dosage of 0.42 mg/L, initial fluoride concentration of 10 mg/L, and pH of 6.8. The result obtained showed 99.3% fluoride removal from the NaF prepared solution and 91.6% fluoride removal from the real sample. The retained properties of GO after adsorption observed on UV-Vis analysis confirmed that the adsorbent can be recyclable. The result obtained also showed that the adsorption kinetics with the coefficient of determination (R-2) for pseudo-second order (SSO) and pseudo-first order (SFO) were 0.99 and 0.96, respectively. Based on these results, the adsorption of fluoride onto GO is a pseudo-second-order kinetics type. According to the result, the Freundlich isotherm model showed a good fit to the experiment with R-2 (0.99). The adsorption capacity of the adsorbent was found to be 301.43 mg/g. Hence, this study showed that GO is the preferred adsorbent for the removal of fluoride from groundwater.

Today, the issue of the environment is the concern of scientists worldwide. Aside from developed countries, developing countries are revolutionizing their economy from agriculture to industries, aggravating the discharge of pollutants. Textile industries are the main sources of pollutant dyes such as methylene blue (MB). In this study, a simple and green synthesis method was used to manufacture a nanostructure heterogeneous photocatalyst, rGO-Bi₂S₃, for the degradation of MB. Bi₂S₃ and rGO were synthesized separately using Vernonia amygdalina (VA) plant extract. rGO-Bi₂S₃ was synthesized using a single-step refluxed hydrothermal method. The products were characterized by XRD, FT-IR, UV-Vis, DTA, TGA, and visual techniques. The comparative degradability degree of the dye under visible light irradiation with and without the presence of the catalyst was studied. The performance test results showed 99 degradation of MB in the presence and 7 in the absence of the catalyst under the same condition for the duration of 25 minutes. The durability and reusability tests for the catalyst were also studied for five cycles. The maximum decrease in the degradation capacity of the catalyst for the duration of 25 minutes was 0.5. Hence, rGO-Bi₂S₃ is found to be the ideal material for the degradation of MB, for environmental protection.