Assessment of the Impact of Modification of Calcium Sorbents and the Possibility of Their Use in Desulfurization for Oxy-Fuel Combustion Process

The paper describes the possibilities of simple and effective modification of calcium sorbents used for flue gas desulfurization with a size between of 125–250 µm. The additives to the sorbents in the amount of 0.5% and 1.0% were inorganic sodium and lithium compounds. The research on the reactivity of sorbents was analyzed in the process of simultaneous calcination and sulfation at the temperature of 850 °C. The type of Na+ or Li+ cations and the inorganic salt anions have an influence on the modification of calcium sorbents in order to improve the efficiency of the calcination and sulfation process. Modification of calcium sorbents by adding inorganic sodium and lithium compounds, regardless of the amount, changes the reactivity coefficient RI [mol/mol] and the absolute sorption coefficient CI [g S/kg sorbent]. In the case of inorganic sodium salt (Additive 1), regardless of the amount of modifier added, there was a visible improvement in the reactivity of the sorbent: 1.0% of the additive caused an increase in the RI coefficient in relation to the raw sorbent by over 14%, and in the case of the CI coefficient by over 24%. Additional research was the analysis of the limestone behavior mechanism during the simultaneous calcination and sulfation (SCS) process under conditions of elevated temperature and with variable CO2 and O2 contents in the flue gas. The behavior of sorbents with a size distribution of 125–250 µm was assessed on the basis of the change in mass of the samples by determining the reactivity coefficient RI, [mol/mol] and the absolute sorption coefficient CI, [g S/kg sorbent]. Using the mercury porosimetry technique, the change in sorbent porosity in the subsequent stages of the simultaneous calcination and sulfation process was investigated. The process was carried out in the temperature range corresponding to the oxy-combustion (i.e., from 850 °C to 1000 °C).

Hydrogeochemical assessment of the sorption properties of heavy metals in the areas of the impact of solid waste landfills on groundwater

Изложены основы методики прогнозирования распространения тяжелых металлов на участках загрязнения подземных вод фильтратом полигонов твердых коммунальных отходов. Выполнен анализ качества фильтрата полигонов твердых коммунальных отходов и применимости статистических и эмпирических оценок коэффициента сорбции тяжелых металлов. Показана ограниченность применимости статистических оценок для анализа распространения высокоминерализованных вод фильтратов. На основе методологии геохимического моделирования разработана модель определения коэффициентов обмена между растворенной и твердой фазами – коэффициентов сорбции. Приведены результаты определения коэффициента сорбции для широкого круга катионов применительно к условиям вытеснения природных вод фильтратом полигонов твердых коммунальных отходов. Разработанная методика может быть использована для оценки влияния полигонов твердых коммунальных отходов на качество подземных вод, для прогнозирования распространения тяжелых металлов в области потенциального влияния отходов, для проведения работ в рамках ОВОС (Оценка воздействия на окружающую среду) и ПМООС (Перечень мероприятий по охране окружающей среды), для разработки систем инженерной защиты подземных вод от загрязнения. Предложенная модель может служить основой для ее дальнейшего развития с учетом процессов образования устойчивых органических комплексов металлов в водах фильтрата и комплексообразования на твердой фазе пород. The fundamentals of the method for predicting the spread of heavy metals in the areas of groundwater pollution by leachate from solid municipal waste landfills are stated. The analysis of the leachate quality of municipal solid waste landfills and the applicability of statistical and empirical estimates of the sorption coefficient of heavy metals is carried out. The limited applicability of statistical estimates for analyzing the distribution of highly mineralized leachate is shown. Based on the method of geochemical simulation, a model has been developed for determining the exchange coefficients between the dissolved and solid phases, i. e. sorption coefficients. The results of determining the sorption coefficient for a wide range of cations are presented with regard to the conditions of natural water displacement by the leachate from solid waste landfills. The developed method can be used to estimate the impact of municipal solid waste landfills on groundwater quality, to predict the spread of heavy metals in the area of potential waste impact, to carry out works within the framework of EIA (Environmental Impact Assessment) and LEPM (List of Environmental Protection Measures), to develop systems for engineering protection of groundwater from pollution. The proposed model can serve as a basis for its further improvement with account of the processes of formation of stable organic metal complexes in leachate and complexation on the hard rocks.

SORPTION OF INDAZIFLAM IN BRAZILIAN SOILS WITH DIFFERENT pH VALUES

ABSTRACT Pre-emergence herbicides, such as indaziflam, have agronomic efficiency when available in the soil solution, mainly in the superficial layer (0-10 cm), the region with the highest concentration of weed seed bank. However, information about the sorption of indaziflam in Brazilian soils still is scarce, since most studies available in the literature were conducted in soils of temperate regions. The objective of this study was to estimate the sorption of indaziflam using high-performance liquid chromatography (HPLC) and bioassay in a Latossolo Vermelho-Amarelo (Oxisol) and in a Cambissolo (Inceptisol), at pH values of 5.1 and 6.1. In the biossay, Sorghum bicolor was used as an indicator plant. Quantitative indaziflam data were obtained by HPLC, and the sorption and desorption coefficients were determined in the soils using Freundlich isotherms. Increasing the pH of the two soils from 5.1 to 6.1 resulted in reductions of C50 and sorption coefficient values. Desorption, a parameter estimated only by HPLC, showed an inverse behavior to that of sorption, that is, the lowest desorption was observed in the condition of highest sorption. It is concluded that the increase in pH of the studied soils reduces indaziflam sorption, influencing the recommendations of this herbicide, from both the agronomic and the environmental points of view. When the goal is to verify the presence or absence of indaziflam in the studied soils, the bioassay technique has satisfactory efficiency. Chromatographic assay is necessary when quantifying the concentration of this herbicide in the soil.

Adsorption and Degradation Behavior of Six Herbicides in Different Agricultural Soils.

This study focuses on the assessment of herbicide adsorption and degradation in three soils (Haplic Chernozem, Haplic Fluvisol, and Arenic Regozem) from different agricultural regions of the Czech Republic where sunflower is cultivated. Soil samples were used in laboratory batch sorption and degradation experiments for six herbicides commonly used on sunflower crops. The findings are used to examine the effect of soil and herbicide properties on adsorption and degradation, as well as to determine the possible relation between the two processes. The (Kf) sorption coefficient ranged from 1.07 to 135.37 cm3/n μg1-1/n g-1, and sorption increased in order: dimethenamid-p < pethoxamid < s-metolachlor < flurochloridone < aclonifen < pendimethalin. Sorption of all six herbicides was positively correlated with organic matter content (p < 0. 001), and cation exchange capacity (p < 0.001). pH was negatively correlated with the sorption of all six compounds (p < 0.001). Degradation rates of herbicides ranged from 0. 012 to 0. 048 day-1, which corresponding to (DT50) half-lives between 14 - 57 days respectively. The longer half-lives were always found in Haplic Fluvisol with higher organic matter content. Results showed that both adsorption and degradation of herbicides is mainly controlled by soil organic matter. A negative relationship was found between the sorption coefficient and the rate of degradation. It can be concluded that the Freundlich sorption coefficient (Kf) can be a good predictor for soil degradation of the studied herbicides.

Gelatin Beads/Hemp Hurd as pH Sensitive Devices for Delivery of Eugenol as Green Pesticide

In this paper gelatin beads reinforced with natural hemp hurd have been produced as pH sensitive devices for the release of eugenol, as green pesticide. The composites beads, with a mean diameter of about 1 mm, were obtained by polymer droplet gelation in sunflower oil. Thermal properties were evaluated showing no noticeable difference after the introduction of hemp hurd. Barrier properties demonstrated an improvement of hydrophobization. The introduction of 5% w/w of hemp hurd led to a reduction of sorption coefficient of about 85% compared to unloaded gelatin beads. Besides, the diffusion coefficient decreased, introducing 5% w/w of hemp hurd, from 8.91 × 10−7 to 0.77 × 10−7 cm2/s. Swelling and dissolution phenomena of gelatin beads were studied as function of pH. The swelling of gelatin beads raised as pH increased up to 2.3 g/g, 9.1 g/g and 27.33 g/g at pH 3, 7 and 12, respectively. The dissolution rate changed from 0.034 at pH 3 to 0.077 h−1 at pH 12. Release kinetics of eugenol at different pH conditions were studied. The released eugenol after 24 h is 98%, 91%, 81 and 63% w/w (pH 3), 87%, 62%, 37 and 32 wt% (pH 7) and 81%, 68%, 60 and 52 wt% (pH 12) for unloaded gelatin beads and gelatin beads with 1%, 3 and 5% of hemp hurd, respectively. The eugenol release behavior was demonstrated to be highly sensitive to the pH release medium, which allows to tune such devices as green pesticide release systems in soils with different level of acidity/basicity.

Adsorption mechanisms of atrazine isolated and mixed with glyphosate formulations in soil

In Brazil, the atrazine has been applied frequently to join with glyphosate to control resistant biotypes and weed tolerant species to glyphosate. However, there are no studies about atrazine's behavior in soil when applied in admixture with glyphosate. Knowledge of atrazine's sorption and desorption mixed with glyphosate is necessary because the lower sorption and higher desorption may increase the leaching and runoff of pesticides, reaching groundwaters and rivers. Thereby, the objective of this study was to evaluate the adsorption mechanisms of atrazine when isolated and mixed with glyphosate formulations in a Red-Yellow Latosol. The maximum adsorbed amount of atrazine in equilibrium (qe) was not altered due to glyphosate formulations. The time to reach equilibrium was shortest when atrazine was mixed with the Roundup Ready® (te = 4.3 hours) due to the higher adsorption velocity (k2 = 2.3 mg min-1) in the soil. The highest sorption of atrazine occurred when mixed with the Roundup WG®, with the Freundlich sorption coefficient (Kf) equal to 2.51 and 2.43 for both formulation concentrations. However, other glyphosate formulations did not affect the sorption of atrazine. The desorption of atrazine was high for all treatments, with values close to 80% of the initial adsorbed amount, without differences among isolated and mixed treatments. The change in the velocity and capacity of sorption for the atrazine mixed with some glyphosate formulations indicates that further studies should be conducted to identify the mechanisms involved in this process.

Influence of Biochar Particulate on the Sorption Behaviour of Sansevieria Cylindrica Reinforced Vinyl Ester Composite

Purpose of this research is to evaluate the influence of biochar from corn cob and wood waste residues on the water resistivity of the Sansevieria cylindrica reinforced vinyl ester composite (SCVEC) to be utilized in structural and marine applications. Biochar filled SCVEC was allowed to immerse in different sources of waters like seawater, ground water and distilled water to study the water absorption of the material. Kinetics of water molecule transferring into the composite during immersion was studied by determining the diffusion coefficient, permeability coefficient and sorption coefficient. Fabricated composites were analysed for its Fickian behaviour under 720 Hrs of immersion in different water medium. Chemical resistivity for the fabricated composite were also studied to make the composite more accessible to marine environment. Results reveals that increase in biochar loading up to certain wt. % increases the water resistivity of the composite. Reinforcement of Biochar derived from corn cob was found to have potential water resistivity property compared to the biochar derived from wood wastes.