Green reduction of graphene oxide (GO) by phytochemicals was explored using the aqueous extract of kaffir lime peels. The research methods included preparation of extracts, preparation of GO, preparation and characterization of reduced-GO (RGO) using Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), and UV-Vis spectroscopy, as well as methylene blue (MB) adsorption test using RGO. The RGO characterization showed that GO was successfully reduced by a C=C group restoration. The MB adsorption kinetics profile in RGO is more suitable for the pseudo-second-order model, whereas for the adsorption isotherm it is more suitable for the Langmuir model with a maximum adsorption capacity (q_max) of 276.06 mg/g at room temperature. The best ratio of GO: kaffir lime peel extract used to prepare RGO was at a ratio of 1: 2. Based on the ΔG, ΔH, and ΔS values, the adsorption of RGO-MB was defined as spontaneous and endothermic process. The results promise the potential application of RGO derived via green route to remove cationic dye in wastewater.

Side effects of drug-based treatment observed in patients during degenerative diseases treatments has directed towards to the identification of plants with antioxidant activity. Kaffir lime peel was selected in this study. This work was aimed to investigate the effect of solvent (hexane, ethyl acetate and n-butanol) polarity on the fractionation of ethanolic crude extract and assess its antioxidative property by DPPH radical scavenging assay. The results show semi polar solvent of ethyl acetate exhibited the best solvent to extract phenolic compounds from ethanolic kaffir lime peel with total phenolic content detected was 0.12 mg Gallic Acid Equivalent/mg. The employment of solvents possessing different polarity resulted several fractions, i.e. hexane, ethyl acetate, n-butanol and residue with different type of phenolic compounds in each fraction. Accordingly, each fraction exhibited different antioxidant activity against free radical compound of DPPH. The N-butanol fraction demonstrated the strongest activity which is shown by lowest IC50 value among the fractions tested. The fraction of n-butanol exhibited the IC50 value of 0.44 mg/mL which means that only 0.44 mg of the fraction/mL is required to inhibit the neutralization of DPPH by 50%. Phenolic identification by High Performance Liquid Chromatography indicates the different phenolic compounds in each fraction that contribute to antioxidative property to different extent. Further investigation to identify these phenolic compounds will lead to further development of kaffir lime as natural antioxidant to treat specific degenerative diseases.

In this study, CNCs were extracted from durian rind. Modification to CNCs with saponin was conducted at 50 °C for one h. CNCs and CNCs-saponin were employed as dexamethasone carriers. Modification to CNCs using saponin did not change the relative crystallinity of CNCs. CNCs’ molecular structure and surface chemistry did not alter significantly after modification. Both nanoparticles have surface charges independently of pH. Dexamethasone-released kinetics were studied at two different pH (7.4 and 5.8). Higuchi, Ritger–Peppas, first-order kinetic and sigmoidal equations were used to represent the released kinetic data. The sigmoidal equation was found to be superior to other models. The CNCs and CNCs-saponin showed burst release at 30 min. The study indicated that cell viability decreased by 30% after modification with saponin.

Kaffir lime peels extract was used as an agent for the reduction of graphene oxide (GO) into reduced graphene oxide (rGO) via a simple room temperature-dispersion process. The GO obtained from the Hummers process is dispersed in polyphenols rich extract at a varied GO-to-extract ratio of 1:1, 1:2, 1:3, and 1:4. The formation of rGO was confirmed through SEM, FTIR, XPS, XRD, and N₂ sorption characterization. The restoration of C=C group and the reduction of several oxygen-containing groups confirmed the successful formation of rGO from GO. The resultant rGOs were used in the adsorption system for methylene blue uptake. The results indicated that the rGOs prepared at a GO-to-extract ratio of 1:2 had the highest adsorption capacity than rGO at other ratios. The XPS spectrum analysis of rGO 1:2 showed a higher C-C/C-O ratio than the other rGOs, indicating a higher number of adsorption sites which aid in improving the adsorption performance. The adsorption isotherm and kinetic studies were conducted to gain insight into the mechanism and rate of methylene blue uptake by the rGOs. The adsorption isotherm systems were consistent with Langmuir isotherm model with the highest adsorption capacity of 118 mg g^–1 by rGO 1:2. The kinetic adsorption data are well represented by the pseudo-second order model, the adsorption equilibrium was achieved within 400 min with the overall uptake rate of 0.3 mg g^–1 min^–1.

In this study, a novel MIL-100(Fe)@TiO₂ composite was synthesized and used as the adsorbent to remove Rhodamine B from synthetic wastewater through adsorption and photocatalytic degradation. The composite was synthesized successfully using solvothermal methods. MIL-100(Fe)@TiO₂ composite has excellent adsorption and photodegradation capability for Rhodamine B removal. The reusability of the materials was observed, with the conclusion that the material still had good adsorption and photocatalytic performance after five cycles of consecutive experiments. The adsorption isotherm, kinetic, and thermodynamic studies of the removal of Rhodamine B were also conducted. The Langmuir model represented the adsorption equilibrium data better than other models. The kinetics of adsorption of Rhodamine B was presented well by pseudo-first-order. The thermodynamic study verified that the physisorption mechanism was more dominant than chemisorption. The addition of Fenton was also proven to be successful in increasing the photocatalytic abilities of the synthesized materials.

Recently, the productivity of porang tuber-based products has been growing well, especially after the Indonesian Government released a policy to prohibit the export of porang plants and their harvested products. One of the porang-based products is in the form of chips. Before processing, the porang tubers must be washed thoroughly to remove soil/dirt from the surface. The conventional washing process of each tuber can take up to 3-5 minutes. Therefore, the purpose of this activity is to design and manufacture porang washing equipment based on centrifuge washing model with rubber vibration. Four stages to carried out the program, i.e. designed and manufactured the washing machine, run the machine in laboratory, training activities to the porang farmers, and evaluation process. From the observation to porang farmers as our partner during the activity, it can be seen that the partners can operate the washing machine well. The results show that the washing process of porang tuber using this technology can save the washing time up to 90% compared to the conventional washing. The surface cleanliness of porang tubers resulted from the developed washing machine is the same as the conventional one. The noise level of the machine has met the requirement of Indonesian Government. It is clear that the usage of the machine can increase the production capacity of products-based porang tuber. In addition, the use of this technology may promote a more comfortable and healthy work environment due to ergonomic reason, however, based on RULA analysis, the machine is still need to be improved in the future. Overall, the partners were satisfied with this activity and expected to have further programs in the future.