We investigated changes in iodine (129I) solubility and speciation in nine soils with contrasting properties (pH, Fe/Mn oxides, organic carbon and iodine contents), incubated for nine months at 10 and 20 °C. The rate of 129I sorption was greater in soils with large organic carbon contents (%SOC), low pH and at higher temperatures. Loss of iodide (I−) from solution was extremely rapid, apparently reaching completion over minutes–hours; iodate () loss from solution was slower, typically occurring over hours–days. In all soils an apparently instantaneous sorption reaction was followed by a slower sorption process for . For iodide a faster overall reaction meant that discrimination between the two processes was less clear. Instantaneous sorption of was greater in soils with high Fe/Mn oxide content, low pH and low SOC content, whereas the rate of time-dependent sorption was greatest in soils with higher SOC contents. Phosphate extraction (0.15 M KH2PO4) of soils, ∼100 h after 129I spike addition, indicated that concentrations of sorbed inorganic iodine (129I) were very low in all soils suggesting that inorganic iodine adsorption onto oxide phases has little impact on the rate of iodine assimilation into humus. Transformation of dissolved inorganic 129 and 129I− to sorbed organic forms was modelled using a range of reaction- and diffusion-based approaches. Irreversible and reversible first order kinetic models, and a spherical diffusion model, adequately described the kinetics of both and I− loss from the soil solution but required inclusion of a distribution coefficient (kd) to allow for instantaneous adsorption. A spherical diffusion model was also collectively parameterised for all the soils studied by using pH, soil organic carbon concentration and combined Fe + Mn oxide content as determinants of the model parameters (kd and D/r2). The kinetic model parameters were not directly related to a single soil parameter; inclusion of pH, SOC, oxide content and temperature was necessary to describe the observed behaviour. From the temperature-dependence of the sorption data the activation energy (Ea) for 129 transformation to organic forms was estimated to be ∼43 kJ mol−1. The Ea value was independent of %SOC and was consistent with a reaction mechanism slower than pore diffusion or physical adsorption, but faster than most surface reactions.\ud \u

A batch process was used to evaluate the potential of regeneration of spent activated carbon (AC) by solvent extraction technique with synergetic to ultra-sonication. Experiments were undertaken as a function of the initial concentration of toluene. Freundlich and Langmuir models were used to study the adsorption isotherms and the data well fitted the Langmuir expression. The maximum adsorption capacities of toluene were found to be 0.108 µg/g activated carbon for Type-I Langmuir. Extraction of the used AC by both methanol solvent and ultrasonic radiation yielded up to 95% reactivation of the spent AC in the first run. Nearly up to 88 % recovery of activity could be achieved after further regeneration and reusing of the spent AC. The results indicate that the coupling of solvent extraction with ultrasonic waves in the AC treatment is comparable and perhaps superior to the conventional regeneration techniques in many cases. This is mainly due to the single step process applied which is less energy consuming; in addition to the nearly comprehensive recovery of the adsorptive capacity of spent AC.

Agricultural wastes such as rice straw, sugar beet, and sugarcane bagasse have become a critical environmental issue due to growing agriculture demand. This study aimed to investigate the valorization possibility of sugarcane bagasse waste for activated carbon preparation. It also aimed to fully characterize the prepared activated carbon (BET surface area) via scanning electron microscope (SEM) and in terms of surface functional groups to give a basic understanding of its structure and to study the adsorption capacity of the sugarcane bagasse-based activated carbon using aqueous methylene blue (MB). The second main objective was to evaluate the performance of sugarcane bagasse-based activated carbon for indoor volatile organic compounds removal using the formaldehyde gas (HCHO) as reference model in two potted plants chambers. The first chamber was labeled the polluted chamber (containing formaldehyde gas without activated carbon) and the second was taken as the treated chamber (containing formaldehyde gas with activated carbon). The results indicated that the sugarcane bagasse-based activated carbon has a moderate BET surface area (557 m²/g) with total mesoporous volume and microporous volume of 0.310 and 0.273 cm³/g, respectively. The prepared activated carbon had remarkable adsorption capacity for MB. Formaldehyde removal rate was then found to be more than 67% in the treated chamber with the sugarcane bagasse-based activated carbon. The plants’ responses for this application as dry weight, chlorophyll contents, and protein concentration were also investigated. Implications: Preparation of activated carbon from sugarcane bagasse (SCBAC) is a promising approach to produce cheap and efficient adsorbent for gas pollutants removal. It may be also a solution for the agricultural wastes problems in big cities, particularly in Egypt. MB adsorption tests suggest that the SCBAC have high adsorption capacity. Formaldehyde gas removal in the plant chambers indicates that the SCBAC have potential to recover volatile gases. The results confirmed that the activated carbon produced from sugarcane bagasse waste raw materials can be used as an applicable adsorbent for treating a variety of gas pollutants from the indoor environment.

Greater Cairo (Egypt) is a megalopolis where the studies of the air pollution events are of extremely high relevance, for the geographical-climatological aspects, the anthropogenic emissions and the health impact. While preliminary studies on the particulate matter (PM) chemical composition in Greater Cairo have been performed, no data are yet available on the PM’s toxicity. In this work, the in vitro toxicity of the fine PM (PM_2.5) sampled in an urban area of Greater Cairo during 2017–2018 was studied. The PM_2.5 samples collected during spring, summer, autumn and winter were preliminary characterized to determine the concentrations of ionic species, elements and organic PM (Polycyclic Aromatic Hydrocarbons, PAHs). After particle extraction from filters, the cytotoxic and pro-inflammatory effects were evaluated in human lung A549 cells. The results showed that particles collected during the colder seasons mainly induced the xenobiotic metabolizing system and the consequent antioxidant and pro-inflammatory cytokine release responses. Biological events positively correlated to PAHs and metals representative of a combustion-derived pollution. PM_2.5 from the warmer seasons displayed a direct effect on cell cycle progression, suggesting possible genotoxic effects. In conclusion, a correlation between the biological effects and PM_2.5 physico-chemical properties in the area of study might be useful for planning future strategies aiming to improve air quality and lower health hazards.