Contaminants of emerging concern (CECs) are chemicals or materials that are not under current regulation but there are increasing concerns about their possible occurrence in the environment because of their potential threat to human and environmental health, with wastewater perceived as their primary source. Although various techniques for their removal from water have been studied, it should be emphasized that the choice should also consider the use of resources and energy within the removal processes, which must be minimized to avoid additional carbon footprints and environmental impact. In this context, the use of biomass-based sorbents might represent a cost-effective and environmentally friendly approach for the removal of CECs from water because they are based on preferably local renewable resources with lower negative impacts on the global carbon cycle through greenhouse gas emissions than the conventional nonrenewable ones. This paper provides an overview of the studies dealing with the application of such so-called biosorbents for the removal of CECs from water and discusses the use of their different forms: sorbents after a minimal pretreatment of the original lignocellulosic biomass; sorbents extracted from lignocellulosic biomass and/or modified; and biochar-based sorbents obtained after thermochemical conversion of biomass. It explains possible modifications of biosorbents and discusses the efficiency of various biosorbents for the removal of selected emerging compounds that belong to the classes of pharmaceuticals, personal care products, and pesticides and compares the adsorption capacities, kinetic models, and mechanisms reported in the relevant literature. Biochar-based sorption has been studied more often if compared to other considered biosorbents. In some cases, removal efficiencies of contaminants greater than 90% were achieved, but nonetheless a wide range of efficiencies for different CECs indicates that for successful simultaneous multicompound removal, a combination of different processes seems to be a more appropriate approach than the stand-alone use of biosorbents. Finally, this review discusses the reasons behind the limited commercial application of the considered biosorbents and provides directions for possible further research, in particular the use of spent biosorbents from a perspective of circular systems.

The main objective of this work was to assess Eucalyptus globulus lignin as an adsorbent and compare the results with kraft lignin, which has previously been demonstrated to be an effective adsorbent. Eucalypt lignin was extracted (by the dioxane technique), characterised, and its adsorption properties for Cr(VI) ions were evaluated. The monomeric composition of both types of lignin indicated a high content of guaiacyl (G) and syringyl (S) units but low content of p-hydroxyphenyl (H), with an H:G:S ratio of 1:50:146 (eucalypt lignin) and 1:16:26 (kraft lignin), as determined by Py-GC/MS. According to elemental analysis, sulphur (2%) and sodium (1%) were found in kraft lignin, but not in eucalypt lignin. The adsorption capacity of the eucalypt lignin was notably higher than the kraft lignin during the first 8 h, but practically all the ions had been absorbed by both the eucalypt and kraft lignin after 24 h (93.4% and 95%, respectively). Cr(VI) adsorption onto both lignins fitted well using the Langmuir adsorption isotherm model, with capacities of 256.4 and 303.0 mg/g, respectively, for eucalypt and kraft. The study’s overall results demonstrate the great potential of eucalypt lignin as a biosorbent for Cr(VI) removal from aqueous solutions.

Wastewater that remains after bioethanol production (stillage) is a major problem from the viewpoint of environmental protection. Besides the large volume, stillage contains high amounts of organic matter, suspended solids, dead yeast cells and their metabolites, so it should not be disposed in the recipient without previous treatment. In this work the possibility of usage of microfiltration for stillage purification was investigated. Also, the application of natural coagulants was investigated, in order to increase the efficiency of microfiltration for stillage treatment. Results obtained after microfiltration showed chemical oxygen demand (COD) reduction of 35% while the combined use of natural coagulants and microfiltration achieved 50% of COD reduction compared to the initial value. Many published works confirmed the activity of natural coagulants on model water but just few of them investigated the activity of natural coagulants in real samples of waters and wastewaters, which makes this paper significant.

One of the major criteria for monitoring water and wastewater quality is turbidity, which is most often reduced using chemical coagulants and flocculants, such as alum and iron salts and acrylamide. However, due to their detrimental effects, intensive investigations into natural coagulants and flocculants have recently been conducted. These coagulants are biodegradable, derived from renewable sources, and do not pose health risks, making them a sustainable solution for water and wastewater treatment. Coagulation and flocculation using natural coagulants is a complex phenomenon influenced by multiple factors. In this study, the impact of the solvent used to extract the natural coagulant from Phaseolus vulgaris seeds on its coagulation effectiveness was examined, along with the effects of pH, the initial turbidity of the treated water, and the applied coagulant dose. The extract obtained using 0.5 mol/L NaCl demonstrated higher coagulation activity compared to the extract obtained with distilled water. Both extracts exhibited improved performance in water with higher initial turbidity (200 NTU) and at the lowest pH tested (pH 6). Under these conditions, the water extract achieved a maximum coagulation activity of 58.4% at a dose of 0.1 mL/L, while the NaCl extract reached an 83.5% turbidity reduction at a dose of 0.4 mL/L. The dominant coagulants in the NaCl extract of Phaseolus vulgaris seeds are anionic polyelectrolytes. In the presence of divalent cations, these coagulants destabilize negatively charged particles through either the bridging mechanism or the sweep coagulation mechanism.

Investigation of an extraction procedure of protein coagulants from common bean seed regarding concentration of NaCl and pH was performed. High values of protein concentration and coagulation activity in crude extract (9.19 g/l and 23.9%, respectively) were obtained when the extraction was performed using 0.5 mol/l NaCl and water as solvent, which represents an advantage for economic and environmental reasons. Crude extract of common bean seed was purified by precipitation at two different percentages of (NH4)2SO4 saturation, followed by batch ion-exchange chromatography. The highest obtained coagulation activity, 45%, was determined in fraction that was eluated at 1.75 mol/l NaCl from resin loaded with proteins precipitated upon 80-100% (NH4)2SO4 saturation. High values of coagulation activity showed by some eluates suggest their application as natural coagulant for water purification. .