Over the past decade, biochar (BC) has received significant attention in many environmental applications, including water purification, since it is available as a low-cost by-product of the energetic valorisation of biomass. Biochar has many intrinsic characteristics, including its porous structure, which is similar to that of activated carbon (AC), which is the most widely used sorbent in water treatment. The physicochemical and performance characteristics of BCs are usually non-homogenously investigated, with several studies only evaluating limited parameters, depending on the individual perspective of the author. Within this review, we have taken an innovative approach to critically survey the methodologies that are generally used to characterize BCs and ACs to propose a comprehensive and ready-to-use database of protocols. Discussion about the parameters of chars that are usually correlated with adsorption performance in water purification is proposed, and we will also consider the physicochemical properties of pollutants (i.e., K_ow). Uniquely, an adsorption efficiency index BC/AC is presented and discussed, which is accompanied by an economic perspective. According to our survey, non-homogeneous characterization approaches limit the understanding of the correlations between the pollutants to be removed and the physicochemical features of BCs. Moreover, the investigations of BC as an adsorption medium necessitate dedicated parallel studies to compare BC characteristics and performances with those of ACs.

In this study, hyperspectral imaging (HSI) was systematically compared with Fourier-transform infrared spectroscopy (FTIR/micro-FTIR) for microplastic (MP) polymer identification using environmental samples collected during a 12-month monitoring campaign at six stations along 300 km of the Po River (Italy), following the Marine Strategy Framework Directive (MSFD, 2008/56/EC) guidelines adapted to freshwater environments. In total, 11,828 MP particles (330 μm-5 mm) were collected and analyzed to assess MP abundance, morphology, color and polymer composition. Across the monitored sites and sampling period, MP concentrations ranged from 0.03 to 12.7 n°/m³, generally lower than values reported for other major world rivers. Fragments and foam dominated the MP categories (56 % and 24 %, respectively), and white was the dominant color (57 %), while PE, PP and EPS were the most abundant polymers (44.9 %, 28.8 % and 22.5 %, respectively). The particle-by-particle comparison between HSI in the short-wave infrared range (1000-2500 nm) and FTIR or micro-FTIR, depending on particle size, yielded an overall polymer identification agreement exceeding 99 %. HSI significantly improved analytical efficiency, requiring only 8 min for classification of 100 particles compared to 300-500 min using FTIR/micro-FTIR spectroscopy. Black MP particles (8 % of the total) were systematically excluded from HSI analysis and characterized exclusively by FTIR/micro-FTIR. The results support the proposal of a new analytical protocol using HSI as the primary tool for polymer classification, with FTIR/micro-FTIR reserved for black or unclassified particles, enabling faster, scalable and reliable MP monitoring.