Adsorption Characteristics and Mechanisms of Fe-Mn Oxide Modified Biochar for Pb(II) in Wastewater

Current progress on manganese in constructed wetlands: Bibliometrics, effects on wastewater treatment, and plant uptake

Constructed wetlands (CWs) are a pollutant treatment design inspired by natural wetlands and are widely utilized for the removal of common pollutants. The research focus lies in the circulation of manganese (Mn) in the environment to enhance pollutant removal within CWs. This paper provides a comprehensive review of recent advancements in understanding the role and effects of Mn in chemical weapons, based on literature retrieval from 2002 to 2021. Ecological risk assessment and heavy metals within CWs emerge as current areas of research interest. Mn sources within CWs primarily include natural deposition, heavy metal wastewater, and intentional addition. The cycling between Mn(II) and Mn(IV) facilitates enhanced wastewater treatment within CWs. Moreover, employing a Mn matrix proves effective in reducing ammonia nitrogen wastewater, organic pollutants, as well as heavy metals such as Cd and Pb, thereby addressing complex pollution challenges practically. To comprehensively analyze influencing factors on the system's performance, both internal factors (biological species, design parameters, pH levels, etc.) and external factors (seasonal climate variations, precipitation patterns, ultraviolet radiation exposure, etc.) were discussed. Among these factors, microorganisms, pollutants, and temperature are the most important influencing factors, which emphasizes the importance of these factors for wetland operation. Lastly, this paper delves into plant absorption of Mn along with coping strategies employed by plants when faced with Mn poisoning or deficiency scenarios. When utilizing Mn for the regulation of constructed wetlands, it is crucial to consider the tolerance levels of associated plant species. Furthermore, the study predicts future research hotspots encompass high-efficiency catalysis techniques, matrix-filling approaches, and preparation of resource utilization methods involving Mn nanomaterials.

Use of different food wastes as green biosorbent: isotherm, kinetic, and thermodynamic studies of Pb2

Lead (Pb2+) can contaminate waters from many sources, especially industrial activities. This heavy metal is an amphoteric, toxic, endocrine-disrupting, bioaccumulative, and carcinogenic pollutant. One of the effective and economical processes used to remove lead from water is adsorption. The fact that the adsorbents used in this method are easily available and will contribute to waste minimization is the primary reason for preference. In this study, the adsorption abilities and surface properties of tea waste (TW), banana peels (BP), almond shells (AS), and eggshells (ES) which are easily available do not need modification and have very high (> 90%) removal efficiencies presented with isotherm, kinetic, and thermodynamic perspectives as detail. The surface structures and elemental distribution of raw adsorbents were revealed with SEM/EDX. Using FTIR analysis, carboxylic (-COOH) and hydroxyl groups (-OH) in the structure of TW, AS, BP, and ES were determined. It was determined that the Pb2+ adsorption kinetics conformed to the pseudo-quadratic model and its isotherm conformed to the Langmuir. The optimum adsorption of Pb2+ was ranked as BP > ES > AS > TW with 100, 68.6, 51.7, and 47.8 mg/g qm, respectively. The fact that the process has negative ΔG° and positive ΔH° values from a thermodynamic point of view indicates that it occurs spontaneously and endothermically. According to the experimental data, the possible adsorption mechanism for Pb2+ has occurred in the form of physisorption (van der Waals, electrostatic attraction) and cooperative adsorption including chemisorption (complexation, ion exchange) processes.