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A coupled ultrasonic extraction process of curcumin from Curcuma longa L enhanced by the graphene-oxide-assisted solvent was developed. The yield was investigated in relation to extraction temperature, extraction time, ethanol volume fraction, and graphene oxide concentration. Response surface methodology was used to develop a quadratic model of the yield and extraction process. The optimum extraction parameters with the highest yield were obtained and the economic value was then assessed. Results showed that the coupling process could reduce the extraction time, extraction temperature, and ethanol volume fraction while improving the extraction yield. The optimal process parameters were 50.0°C extraction temperature, 1.5 h extraction time, 60.0% ethanol volume fraction, and 1.0 mg/g graphene oxide concentration. The highest extraction yield was 64.9 mg/g, which was better than that have been reported. It can save an estimated $1507 in production expenses for every ton of turmeric under the optimal extraction process. Moreover, the reduction in extraction temperature and ethanol volume fraction also means a safer and cleaner production environment, which highlights the greater potential application prospect of the extraction process developed in this paper. [ABSTRACT FROM AUTHOR]

The service life of artificial joints has gradually failed to meet the needs of patients. Herein, the synergistic lubrication and antioxidant efficacies of graphene oxide (GO) and fullerenol (Fol) as biological lubricant additives for artificial joints were investigated. The lubrication mechanisms of biological lubricant containing GO and Fol at the friction interface of artificial joints were then revealed. Tribological tests showed that the average friction coefficients of Al2O3–Ti6Al4V pairs and Ti6Al4V–UHMWPE pairs for artificial joints could be reduced by 30% and 22%, respectively, when GO and Fol were used as biological lubricant additives simultaneously. The lubrication mechanism showed that some incommensurate sliding contact surfaces could be formed between the GO nanosheets and spherical Fol at the interface, which reduced the interaction forces of friction pairs. The maximum scavenging rates of •OH and DPPH free radicals by the biological lubricant containing GO and Fol were 35% and 45%, respectively, showing a good antioxidant efficacy of the biological lubricant. This can be attributed to the GO and Fol scavenging free radicals through electron transfer and hydrogen transfer. This study provides a theoretical basis for the development and application of carbon nanomaterials as biological lubricant additives for artificial joints in the future. [ABSTRACT FROM AUTHOR]