Assessment of Emerging Particulate Contaminants in Industrial Wastewater Using Advanced ICP-MS Techniques

Abstract

The increasing use of nanomaterials in modern industries and consumer products has led to the release of various contaminants into wastewater streams and the surrounding environment. However, nanoparticle detection and characterisation in wastewater remain analytically challenging due to the presence of dissolved metals, suspended solids, natural colloids, and heterogeneous particulate matter. In this study, we demonstrate an integrated analytical workflow combining single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) with transmission electron microscopy (TEM) and ImageJ version 1.54g image analysis for the comprehensive characterisation of engineered nanoparticles (ENPs) in industrial wastewater. In contrast to earlier research on well-defined manufactured nanoparticles in controlled laboratory suspensions, this work uses complementary analytical techniques to analyse real industrial wastewater, allowing for quantitative elemental analysis, particle sizing, and morphological confirmation in South Africa. Additionally, a supporting bibliometric analysis serves as supporting evidence to identify research trends and knowledge gaps, revealing limited application of integrated analytical workflows to complex industrial wastewater matrices. Analytical conditions were optimised according to the recommendations of previous publications, with a dwell period of 3 μs to limit particle coincidence and enable reliable single-particle detection. The combined approach was effectively applied to characterise silver (AgENPs) and gold (AuENPs) nanoparticles with median particle sizes of 14 nm and 8 nm, respectively. The particle number concentrations ranged from 3.00 × 107 to 3.60 × 108 particles L−1 for AgENPs and 3.80 × 108 particles L−1 for AuENPs. Comparing dissolved metal concentrations with particle mass concentrations gave some insight into the partitioning of metals between the dissolved and nanoparticulate fractions. Moreover, bibliometric analysis has shown that despite the exponential growth of research on SP-ICP-MS, very few studies have simultaneously employed analytical techniques to describe nanoparticles in complicated industrial wastewater matrices. These results show the utility of integrating complementary analytical approaches for the reliable characterisation of particulate pollutants in environmentally relevant samples and promote improved environmental monitoring and risk assessment of manufactured nanoparticles.