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New insights into pyrite-hydrogen peroxide interactions during froth flotation : experimental and DFT study

Cao Qinbo, Yan Wenchao, Wen Shuming, Liu Dianwen, Li Yanjun

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 1

art. no. 157409

EN

Hydrogen peroxide (H2O2) is an efficient depressant for pyrite (FeS2) flotation. However, the depressing mechanism of H2O2 is not fully understood. In this paper, the depressing capacity of H2O2 for pyrite was examined by flotation tests. Results revealed that pyrite flotation could be inhibited by H2O2 at pH 6.4. The pyrite powder in H2O2 solution enhanced the release of O2 from H2O2. However, the O2 concentration in the solution was less than that of H2O2; thus, H2O2 is the major oxidant in the solution. Moreover, density functional theory calculations were performed to study the interactions between H2O2 and hydrated pyrite (100) surface. The H2O2 molecule tended to react with the pyrite surface to generate one S=O bond and an H2O molecule. The possible binding models of O2 molecules on the pyrite (100) surface were also studied for comparison. The O2 dissociation on the pyrite surface was more favorable than the adsorption of O2 as a whole. In addition, the orbital interaction in the S=O bond raised from the reaction of H2O2/O2 with the pyrite surface was also investigated by the density states analysis. These results provide some insights into the oxidizing effect of H2O2 in pyrite flotation.

2

Comparative effectiveness of biochar derived from tropical feedstocks on the adsorption for ammonium, nitrate and phosphate

Zou Ganghua, Shan Ying, Dai Minjie, Xin Xiaoping, Nawaz Muhammad, Zhao Fengljang

Archives of Environmental Protection

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2022

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Vol. 48, no. 4

25--34

EN

Biochar has been extensively studied as a soil amendment to reduce nutrients losses. However, the comparative effectiveness of biochar adsorption capacity for ammonium (NH4 -N), nitrate (NO3 -N), and phosphate (PO4-P) remains unknown. In the present study, the effects of feedstock (banana stem and coconut shell) and temperature (300, 500, and 700°C) on biochar adsorption ability for NH4-N, NO3-N, and PO4-P were investigated and fitted by three adsorption models, viz Freundlich, Langmuir, and linear. Freundlich (R2 = 0.95–0.99) and Langmuir (R2 = 0.91–0.95) models were found suitable for adsorption of NH4 -N. The maximum adsorption capacity (Qm) for coconut shell biochar increased with pyrolysis temperature (Qm = 12.8–15.5 mg g-1) and decreased for banana stem biochar (Qm = 12.9–9.7 mg g-1). In the case of NO3 -N adsorption, Freundlich (R2 = 0.82–0.99) and linear model (R2 = 1.00) were found suitable while Langmuir model showed much less contribution, similarly adsorption of PO4-P, was not supported by these three models. The minimum concentrations required for adsorption of phosphate were recorded as 36, 8, and 3 mg L-1 using pyrolyzed biochar at the temperatures of 300, 500, and 700°C, respectively. These results indicate that the feedstock and pyrolysis temperature, as well as aquatic nutrient concentration, were important factors for the adsorption of inorganic nitrogen and phosphorus.

3

Adsorpcja dwufunkcyjnych labilnych surfaktantów kationowych na granicy faz ciecz/gaz : opis za pomocą modelu kwazi-dwuwymiarowego elektrolitu

Frąckowiak Renata, Para Grażyna, Lamch Łukasz, Szyk-Warszyńska Lilianna, Wilk Kazimiera A., Warszyński Piotr

Wiadomości Chemiczne

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2021

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[Z] 75, 9-10

1119--1155

EN

There is an increasing interest in surfactants that comprise a linkage that breaks down in a controlled way. The most known examples of the cleavage mechanism include acid or alkaline hydrolysis, UV irradiation, enzymatic or heat decomposition. For practical reasons, the labile grouping can be inserted between the hydrophobic tail of the surfactant and the polar head group. Chemically and/or enzymatically induced cleavage of this labile bond would cause the separation of the polar part and the hydrophobic tail and, consequently, change of surface activity, an event usually referred to as the primary degradation of the surfactant. Dicephalic labile cationic surfactants belong to the class of surface active compounds with many potential applications often associated with their biological activity for a wide range of bacteria, viruses, fungi, or algae. Thus, they can be used in disinfecting agents or for protecting against the occurrence of these microorganisms. They adsorb well on negatively charged surfaces, which can be used in the treatment of fabrics. Due to excellent antistatic properties, they can be used for the final rinsing of fabrics, especially synthetic ones. In flotation processes, they can act as collectors, and in catalysis, they can be used as phase transfer catalysts or templates for zeolite synthesis. We present the surface quasi-two-dimensional electrolyte (STDE) model as a universal model for the description of ionic surfactants’ adsorption at fluid interfaces that explicitly considers the electric double formation upon surfactant adsorption. The model was adapted to describe phenomena occurring for adsorption of dicephalic surfactants as counterion specificity or formation of surfactant ioncounterion associates. As an example, we applied the model to explain the mechanism of adsorption at water/air interface of novel dicephalic cationic surfactants, N,N-bis[3,3′-(trimethylammonio)propyl]alkylamide dibromides and N,N-bis[3,3′-(trimethylammonio)propyl]alkylamide dimethylsulfates, both belonging to the class of chemodegradable surfactants having amide bond between two quaternary amine cationic groups and a single hydrophobic tail. Additionally, we used the same model to describe adsorption isotherms of N,N-bis[3,3- (dimethylamine)propyl]alkylamide dichlorides, having as two hydrophilic groups tertiary amines, which charge is pH-dependent. Application of the STDE model allowed an excellent description of experimental adsorption isotherm of dicephalic cationic surfactants and explained the specific features connected with the presence of multicharged headgroup.

4

In-situ nitrate remediation using nano iron/nickel particles

Tehrani M. R. F., Vossoughi M., Shamsai A.

Environment Protection Engineering

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2014

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Vol. 40, nr 3

75--86

EN

Originally, the application of nano zero valent iron/nickel (nZVI/Ni) particles for nitrate removal in porous media was studied. nZVI/Ni was prepared and employed in batch and continuous modes. Based on batch experiments, the reaction kinetics was consistent with the adsorption model by the order of 1–1.5. The variation of the kinetics order depends on pH and nickel content. So that highest reactivity was observed for nZVI with 10% of Ni at pH ≤ 3. Nitrate remediation in a continuous system was mostly influenced by seepage velocity, quantity and freshness of nZVI/Ni and particle size of porous media. In a batch mode, the maximum nitrate removal was 99% while in a continuous mode it did not exceed 85%.

5

Dependence of adsorption/diffusion processes in porous media on bulk and surface permeabilities

Albers B.

Archives of Mechanics

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2001

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Vol. 53, nr 4-5

289-306

EN

The paper contains a macroscopic continuum model for adsorption in porous materials (B. Albers [1, 2]) which is an extension of the model for porous bodies by K. Wilmański [7] on mass exchange processes. We consider the flow of a fluid/adsorbate mixture through channels of a solid component. The fluid serves as carrier for an adsorbate whose mass balance equation contains a source term. Due to low adsorbate concentration we deal with a physical adsorption process which means that particles of the adsorbate stick to the skeleton due to weak van der Waals forces. The model contains two different permeability parameters whose nature is completely different: The first one, the usual bulk permeability coefficient, describes the resistance of the skeleton to the flow of the fluid/adsorbate mixture. The second one describes the surface resistance to the outflow of the mixture from the solid. This work shows within a simple example the range of these parameters and the dependence of adsorption/diffusion on them.