Food Waste Materials as Low-Cost Adsorbents for the Removal of Volatile Organic Compounds from Wastewater

Untreated plant waste of the Mediterranean region as bioadsorbent of persistent organic pollutants

The excessive and/or improper use of plant protection products (PPPs) can generate alarming levels of residues in the environment, compromising both soil fertility and food safety. Various organic wastes released in large amounts by agro-industrial activity are currently studied and applied as bioadsorbents for water and soil decontamination. This study explored the capacity of untreated orange peel, olive stones and pistachio shells to adsorb the PPPs oxyfluorfen (OXY), metribuzin (MET) and imidacloprid (IMI), and the xenoestrogen bisphenol A (BPA) from water. The physicochemical, microstructural, and spectroscopic characteristics of the adsorbents were first evaluated using TXRF, SEM and FTIR-ATR techniques. Adsorption kinetics showed that each pollutant was rapidly (∼24 h) retained by all adsorbents according to a pseudo-second order model, which suggested a prevalent chemisorption. Interpretation of the sorption isotherm data with various theoretical equations showed that all molecules on all adsorbents preferentially followed the Freundlich model. Among the materials, olive stones showed the highest adsorbent capacity with KF values equal to 713, 317, 359 and 736 mg kg-1 for OXY, MET, IMI, and BPA, respectively. The desorption of each compound from all materials was hysteretic. Based on the overall results obtained, it appears that all three materials tested may have interesting applications for the retention of organic pollutants, especially very hydrophobic ones. This paves the way for further investigations into natural adsorbents as sustainable tools for environmental remediation.

The role of sustainable materials in sample preparation

Sample preparation is a constantly evolving step in the measurement process with a positive effect on its performance. Its evolution has been marked by an underlying environmental commitment, with simplification, miniaturization, and automation being three of its driving forces. This trends article deepens how the sample preparation can go sustainable through the efficient design of new sorptive materials, either liquid or solid. This objective can be achieved by using natural and/or biodegradable materials as precursors of the functional sorptive phases and by designing materials that simplify the procedures (thus reducing the energy or resources required). Although environmental performance is a crucial aspect of a new material, its applicability is what really defines its incorporation into the sample preparation toolbox. For this reason, their characteristics and more relevant applications will be briefly presented to conclude with the tendency of their use in the very near future.

Municipal Sewage Sludge as a Source for Obtaining Efficient Biosorbents: Analysis of Pyrolysis Products and Adsorption Tests

In the 21st century, the development of industry and population growth have significantly increased the amount of sewage sludge produced. It is a by-product of wastewater treatment, which requires appropriate management due to biological and chemical hazards, as well as several legal regulations. The pyrolysis of sewage sludge to biochar can become an effective way to neutralise and use waste. Tests were carried out to determine the effect of pyrolysis conditions, such as time and temperature, on the properties and composition of the products obtained and the sorption capacity of the generated biochar. Fourier transform infrared analysis (FTIR) showed that the main components of the produced gas phase were CO₂, CO, CH₄ and to a lesser extent volatile organic compounds. In tar, compounds of mainly anthropogenic origin were identified using gas chromatography mass spectrometry (GC-MS). The efficiency of obtaining biochars ranged from 44% to 50%. An increase in the pyrolysis temperature resulted in a decreased amount of biochar produced while improving its physicochemical properties. The biochar obtained at high temperatures showed the good adsorption capacity of Cu²⁺ (26 mg·g^-1) and Zn²⁺ (21 mg·g^-1) cations, which indicates that it can compete with similar sorbents. Adsorption of Cu²⁺ and Zn²⁺ proceeded according to the pseudo-second-order kinetic model and the Langmuir isotherm model. The biosorbent obtained from sewage sludge can be successfully used for the separation of metal cations from water and technological wastewater or be the basis for producing modified and mixed carbon sorbents.

Mechanistic insights into carbo-catalyzed persulfate treatment for simultaneous degradation of cationic and anionic dye in multicomponent mixture using plastic waste-derived carbon

Upcycling waste into value-added products for utilization in wastewater abatements has been explored in a number of treatment technologies. One such waste, single-use plastic, which poses significant adverse environmental and economic impact, has been chosen and converted into graphitic carbon to reduce the waste burden sustainably and economically. The sorptive and catalytic performance of synthesized plastic waste-derived carbon (PWC) was evaluated using brilliant green (BG) and eosin yellow (EY) as target pollutants. The adsorption capacity of PWC was very low for BG (7.41 mg/g) and EY (4.93 mg/g). The coupling of PWC with peroxymonosulfate (PMS) promoted dye degradation. Complete degradation of the dye, with ~61% reduction in TOC and ~95% reduction in toxicity, was achieved by oxidative treatment (initial concentration: 10 mg/L). The functionalities of PWC facilitated better electron transfer to PMS for its effective activation, which led to the production of SO₄^•- and OH^•. The quenching study confirmed that the degradation of dyes was primarily due to SO₄^•-. Additionally, the pathways of dye degradation were proposed based on the intermediates identified. Thus, this study established the high potential of PWC as a metal-free catalyst in PMS activation for the abatement of organic pollutants.