Sequentially optimized process towards sustainable synthesis of activated carbon from wild thornbush for 4-nitrophenol and industrial effluent treatment.

Environmental nuisance thornbush Prosopis juliflora was utilized as an inexpensive and renewable biomass raw material for the sustainable production of activated carbon. Previously, the sequential muffle furnace-microwave arrangement was effective with acid activation for activated carbon synthesis. However, the intermediate synthesis steps were not optimized. In this work, we have optimized the intermediate steps, viz. chemical impregnation, carbonization, and microwave activation. Sequential optimization for base activation was developed and compared with acid activation. The base-activated carbon (BAC) exhibited a more crystalline nature and faster uptake kinetics than AAC. BAC demonstrated an adsorption capacity of 576 mg/g for 4-nitrophenol (4-NP) surpassing that of optimized acid-activated carbon (AAC) by 45%. The optimal base activation required 1.85 times lower microwave energy than that of the acid activation. BAC exhibited significantly higher BET surface area (1319 m2/g) and micropore volume (0.524 cm3/g) which were about 28% and 26% higher than those of AAC. When compared to biochar obtained from the same thornbush, the BAC exhibited an 11-fold increase in adsorption capacity. The adsorbents could be easily regenerated with ethanol and used up to five cycles. Adsorption using BAC also could achieve 80% COD removal for industrial wastewater, while AAC led to 61% removal. Continuous packed column with BAC revealed a breakthrough time of 3.5 h for industrial effluent while for 500 mg/L 4-nitrophenol, it was 25 h. Prosopis juliflora thornbush, an environmental nuisance, could be converted into a high-capacity adsorbent for environmental remediation after careful sequencing and optimization of the intermediate synthesis steps.

Fabrication of laser printed microfluidic paper-based analytical devices (LP-µPADs) for point-of-care applications.

Microfluidic paper-based analytical devices (µPADs) have provided a breakthrough in portable and low-cost point-of-care diagnostics. Despite their significant scope, the complexity of fabrication and reliance on expensive and sophisticated tools, have limited their outreach and possibility of commercialization. Herein, we report for the first time, a facile method to fabricate µPADs using a commonly available laser printer which drastically reduces the cost and complexity of fabrication. Toner ink is used to pattern the µPADs by printing, without modifying any factory configuration of the laser printer. Hydrophobic barriers are created by heating the patterned paper which melts the toner ink, facilitating its wicking into the cross-section of the substrate. Further, we demonstrate the utilization of the fabricated device by performing two assays. The proposed technique provides a versatile platform for rapid prototyping of µPADs with significant prospect in both developed and resource constrained region.