The resistance random access memory (RRAM) based on biomaterials has great potential application in the sustainable electronic devices with the advantages of being sustainable, green, and environment-friendly, and it can offer a potential route for developing bio-RRAM devices, which would be a competitive bench in development of multipurpose memory devices. In our work, the banana peel, an ubiquitous useless waste, is introduced as an intermediate insulating material to preparing resistive switching memory device with Ag/Banana peel/Ti structure, in which the superior switching memory performance with a lager high resistance state/low resistance state resistance ratio and long retention characteristics are revealed. Moreover, the coexistence of memristor effect, capacitance effect, and negative differential resistance phenomenon are observed in our device. The repeatable nonvolatile resistive switching memory behaviors are attributed to the redox properties of metal cations contained in biomaterials.

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Recycling sewage sludge by pyrolysis has attracted increasing attention for pollutant removal from wastewater and soils. This study scrutinized As(III) sorption behavior on sludge-derived biochar (SDBC) under different pyrolysis conditions and solution chemistry. The SDBC pyrolyzed at a higher temperature showed a lower As(III) sorption capacity and increasingly nonlinear isotherm due to loss of surface sites and deoxygenation-dehydrogenation. The Langmuir sorption capacity on SDBC (3.08-6.04 mg g) was comparable to other waste-derived sorbents, with the highest As(III) sorption on SDBC pyrolyzed at 400°C for 2 h. The As(III) sorption kinetics best fit with the pseudo-second-order equation, thus suggesting the significance of the availability of surface sites and initial concentration. Sorption of As(III) was faster than that of Cr(VI) but slower than that of Pb(II), which was attributed to their differences in molar volume (correlated to diffusion coefficients) and sorption mechanisms. The X-ray photoelectron spectra revealed an increase of oxide oxygen (O) with a decrease of sorbed water, indicative of ligand exchange with hydroxyl groups on SDBC surfaces. The As(III) sorption was not pH dependent in acidic-neutral range (pH < 8) due to the buffering capacity and surface characteristics of the SDBC; however, sorption was promoted by increasing pH in the alkaline range (pH > 8) because of As(III) speciation in solution. An increasing ionic strength (0.001-0.1 mol L) facilitated As(III) sorption, indicating the predominance of ligand exchange over electrostatic interactions, while high concentrations (0.1 mol L) of competing anions (fluoride, sulfate, carbonate, and phosphate) inhibited As(III) sorption. These results suggest that SDBC is applicable for As(III) immobilization in most environmentally relevant conditions.

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