Treatment of intermediate landfill leachate using different anode materials in electrooxidation process

This study aims to investigate the performances of widely used anode materials in the treatment of intermediate landfill leachate treatment by electrooxidation (EO) process. The raw leachate was collected from an 8-year-old landfill facility and had a chemical oxygen demand (COD) of 4660 mg/L, biological oxygen demand (BOD5) of 1370 mg/L, and total organic carbon (TOC) of 2260 mg/L. TOC and COD removal efficiencies of Boron-Doped Diamond (BDD), Pt, and four different Ti-based mixed metal oxide (MMO) anodes ((RuO2-TiO2, RuO2-IrO2, PtO2-IrO2, and IrO2-Ta2O5) were compared at the current densities of 25 mA/cm(2), 75 mA/cm(2), and 125 mA/cm(2). At the highest current density, the BDD achieved 100% TOC and COD removal efficiencies in 240 min. BDD was followed by the Pt anode, which achieved 95.53% COD and 92.74% TOC removal efficiencies. The Pt electrode also had the lowest SEC values at all current densities. Although the performances of four MMO electrodes were very close, RuO2-TiO2 achieved a slightly higher performance than the others. It was concluded that Pt anode can be a promising alternative to BDD, which was 18 times more expensive, with its comparable pollutant removal performance and low specific energy consumption

Hydrochars as Emerging Biofuels: Recent Advances and Application of Artificial Neural Networks for the Prediction of Heating Values

In this study, the growing scientific field of alternative biofuels was examined, with respect to hydrochars produced from renewable biomasses. Hydrochars are the solid products of hydrothermal carbonization (HTC) and their properties depend on the initial biomass and the temperature and duration of treatment. The basic (Scopus) and advanced (Citespace) analysis of literature showed that this is a dynamic research area, with several sub-fields of intense activity. The focus of researchers on sewage sludge and food waste as hydrochar precursors was highlighted and reviewed. It was established that hydrochars have improved behavior as fuels compared to these feedstocks. Food waste can be particularly useful in co-hydrothermal carbonization with ash-rich materials. In the case of sewage sludge, simultaneous P recovery from the HTC wastewater may add more value to the process. For both feedstocks, results from large-scale HTC are practically non-existent. Following the review, related data from the years 2014–2020 were retrieved and fitted into four different artificial neural networks (ANNs). Based on the elemental content, HTC temperature and time (as inputs), the higher heating values (HHVs) and yields (as outputs) could be successfully predicted, regardless of original biomass used for hydrochar production. ANN3 (based on C, O, H content, and HTC temperature) showed the optimum HHV predicting performance (R2 0.917, root mean square error 1.124), however, hydrochars’ HHVs could also be satisfactorily predicted by the C content alone (ANN1, R2 0.897, root mean square error 1.289)

Anodic oxidation of bisphenol A by different dimensionally stable electrodes

Abstract Bisphenol A (BPA) is a known endocrine disrupter and was detected in surface waters. We investigated the mineralization of BPA by electrochemical oxidation. Six different types of electrodes, including the boron-doped diamond (BDD), platinum (Pt), and mixed metal oxide (MMO) electrodes; RuO2–IrO2, RuO2–TiO2, IrO2–Ta2O5, and Pt–IrO2, were compared as the anode material. Total organic carbon (TOC) was analyzed to monitor the mineralization efficiency of BPA. BDD achieved 100% BPA mineralization efficiency in 180 min and at a current density of 125 mA/cm2, whereas the TOC removal efficiency of Pt was 60.9% and the efficiency of MMO electrodes ranged between 48 and 54%. BDD exhibited much lower specific energy consumption, which corresponds to a lower energy cost (USD63.4 /kg TOC). The effect of operational parameters showed that the BDD anode was much more affected by the current density, initial BPA concentration, and electrolyte concentration than the other parameters such as the stirring speed and interelectrode distance.</jats:p