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Salt-tolerant superabsorbent polymer (SAP) was synthesized to improve the water retention properties of saline-alkali soil. The Lop Nur saline-alkali soil of Xinjiang with high salinity (total dissolved salt: 18.13wt%) was the object of improvement. The good swelling capacity of SAP (69.04 g/g) under high salinity condition contributed to the superb slow-release water property and further [showed](https://www.wordhippo.com/what-is/another-word-for/build.html) [excellent](https://www.wordhippo.com/what-is/another-word-for/excellent.html) water retention property of SAP-saline-alkali soil (28 days), which showed a good application potential of SAP in saline-alkali land. The swelling mechanism under high salt condition was also explored. Notably, owe to the complexation reaction between and three hydrophilic groups of SAP, the swelling capability of SAP tended to keep steady when the concentration of CaCl exceeded 0.55wt%. Interestingly, the distribution of the calcium salt in SAP was directly displayed by the maximum intensity projection of computed tomography.

The establishment of biological soil crusts is widely perceived as a main method to control ecological environment in arid and semi-arid regions. However, artificial biocrusts are insufficient to face with some stress from environment by using traditional established methods. Hence in this study, kaolin, a common clay mineral, was introduced as a stabilizer by mixing with Microcoleus steenstruppi of different mass ratios for inoculating onto sand to establish artificial biocrust. The results showed that the addition of kaolin exhibited a significantly positive effect on promoting biocrust formation, and accelerating the biocrust development. Moreover, the artificial biocrust from 1:500 (algae:kaolin) inoculant achieved the best performances with coverage of 98%, and thickness of 5.62 mm after 86 days of incubation. The highest contents of chlorophyll a, exopolysaccharides, and soluble protein were also observed in 1:500 mass ratio of algae:kaolin throughout the biocrust development process. As for the water retention performances, the results of contact angle, water drop penetration time (WDPT), and repellency index (RI) illustrated that biocrusts improve water utilization in kaolin-treated groups by delaying the time of water infiltration, especially in 1:500 group. After 86 days post inoculation, a series of common bacteria appeared in the biocrusts such as actinobacteria and acidobacteria and decomposed metabolites from cyanobacteria as energy source to supply their own life activities. This study gains new insights on clay minerals on biocrust development and puts forward a new approach for rapid artificial biocrust establishment to reverse desertification.

The purpose of this paper is to provide an overview of the Climate Change (CC) in the Central African Republic (CAR). Many researches on strategies to fight CC and reduce Green House Gas (GHGs) emissions have been conducted. However, implementation poses a serious problem at different levels including political, economic and socio-environmental. CC is seen as one of the greatest challenges of the 21st century. The CAR, like other countries of the world, has ratified the Kyoto Protocol on 1st January 2008, which aims to reduce the GHGs emissions responsible for CC. Almost all sectors (Energy, Agriculture, Forest, Health, Transport, Economy...) are affected by CC. GHGs are abundant in the Earth's atmosphere. In the absence of efficient meteorological equipment and stations to save accurate data, the CAR and even Africa in general is considered a "black hole" of climate information which must be used by the Intergovernmental Panel-evolution of Climate change (IPCC) to evaluate effects of CC on the continent. Despite its low level of GHGs emissions, the CAR reaffirms its adherence to the principle of collective responsibility. Pursuant to 1CP / 19 (Further advancing the Durban Platform) by these ambitious measures to meet this challenge. Thus, in the CAR, political, military and economic constraints are obstacles to the implementation of strategies to fight CC. Given its low level of development, 80% of rural population, forests and lands of the CAR are the most affected by CC; These impacts in all sectors are very difficult to assess due to the lack of reliable data, of its very weak economy and the multiple armed conflicts that do not make the collection and updating of data easy, almost half of the territory 14 prefectures on 16 have been occupied by armed groups.

This paper aims at demonstrating the significance of biochar risk evaluation and reviewing risk evaluation from the aspects of pyrolysis process, feedstock, and sources of hazards in biochar and their potential effects and the methods used in risk evaluation. Feedstock properties and the resultant biochar produced at different pyrolysis process influence their chemical, physical, and structural properties, which are vital in understanding the functionality of biochar. Biochar use has been linked to some risks in soil application such as biochar being toxic, facilitating GHGs emission, suppression of the effectiveness of pesticides, and effects on soil microbes. These potential risks originate from feedstock, contaminated feedstock, and pyrolysis conditions that favor the creation of characteristics and functional groups of this nature. These toxic compounds formed pose a threat to human health through the food chain. Determination of toxicity levels is a first step in the risk management of toxic biochar. Various sorption methods of biochar utilized low-cost adsorbents, engineered surface functional groups, and nZVI modified biochars. The mechanisms of organic compound removal was through sorption, enhanced sorption, modified biochar, postpyrolysis thermal air oxidation and that of PFRs degradation was through activation, photoactive functional groups, magnetization, and hydrothermal synthesis. Emissions of GHGs in soils amended with biochar emanated through physical and biotic mediated mechanisms. BCNs have a significance in reducing the health quotient indices for PTEs risk contamination by suppressing cancer risk arising from consumption of contaminated food. The degree of environmental risk assessment of HM pollution in biomass and biochars has been determined by using potential ecological risk index and RAC while organic contaminant degradation by EPFRs was considered when assessing the environmental roles of biochar in regulating the fate of contaminants removal. The magnitude of technologies’ net benefit must be considered in relation to the associated risks.

The porous La(III)- montmorillonite hydrogel beads (La-MMT_hb) with stable structure were fabricated via hydrogen-bond and electrostatic interactions for arsenic removal from water. The structural characteristics of La-MMT_hb and its sorption performances for As(V) were evaluated. The results showed that porous La-MMT_hb were clearly observed by scanning electron microscopy, and the addition of lanthanum significantly increased the specific surface area. The maximum adsorption capacity of La-MMT_hb for As(V) was 58.75 mg/g, reached within 4 h, at the optimum pH of 4 with optimum La dosage of 1%. The mechanism of adsorption can be attributed to the electrostatic forces between La(III) and H2AsO4− at pH 4, ion exchange of O H groups on the surface of adsorbent with H2AsO4− and complex chelate formation as.-NH3-H2AsO4 and -La-O-As.

Physicochemical Problems of Mineral Processing; ISSN 2083-3989

"Amorphous Ni(OH)2 coating on nanostructured nickel scaffolds with rational archietcture have been successfully fabricated by a facile process of templated-directed electrodeppsition and surface oxidation treatment. Nitrocellulose membrane with interconnected fibers and fiber diameter of a few hundred nanometers was used to fabricate nanoprpous nickel (NPN) at low cost. The as-prepared NPN has interconnected pore channels with pore diameter of a few hundred nanometers providing enough inner space for the formation of Ni(OH)2 nanosheets and short pathways for fast diffusion of electrolyte ions. Upright self-supported nickel nanowire array (USNWA) and self-supported nickel nanowire array (INWA) were fabricated with porous polycarbonate template and porous polyester template, respectively. Both of USNWA and INWA can be used as miniature conductive scaffolds ensuring excellent electrical/ionic conductivity, and providing large surface area. The amorphous Ni(OH)2 nanosheets coating on the miniatuer nickel scaffold was converted from the metallic surface by oxidation treatment. The conversion of metallic surface to amorphous Ni(OH)2 nanosheets creates a stable core-shell structure, a low contact resistane and guarantees a high utilization of Ni(OH)2. Because of the material and architecture advantages, the Ni(OH)2@NPN/USNWA/INWA show enhanced electrochemical performance of ultrahigh specific capacities more than 3500 F g-1 at a current density of 5 A g-1, remarkable rate capability and excellent cycling stability. The asymmetric supercapacitor of Ni(OH)2@INWA//rGO delivers a high energy density of 53 Wh kg-1 at a power density of 395 W kg-1, and an energy density of 31 Wh kg-1 can be maintained at a power density of 4973 W kg-1. It also shows long-term stability with 91 % retention of the initial capacitance after 10000 cycles at a current density of 2 A g-1. The excellent electrochemical performance of Ni(OH)2@NPN/USNWA/INWA makes them promising for supercapacitor applications."

Chalcopyrite flotability were investigated in four common chloride salts. The results indicated that NaCl, KCl, CaCl2 increased chalcopyrite recovery while MgCl2 decreased its recovery. The monovalent salts played an insignificant role while divalent salts apparently decreased the contact angle of chalcopyrite, regardless of the presence of collectors. Furthermore, the zeta potential was increased in divalent salts and even changed from negative to positive values in MgCl2, highly due to Mg(OH)2 precipitation on chalcopyrite surface. In addition, molecular dynamics simulation indicated that Mg(OH)2 precipitates on chalcopyrite (112) surface stabilized the liquid layer and formed a hydrophilic barrier to inhibit SBX adsorption Refereed/Peer-reviewed

Due to regional shortage of freshwater, the use of saline/seawater for Cu-Mo sulfide ore flotation has received considerable attention. However, the effects of various salts, especially the cations present in seawater, onmolybdenite flotation and the mechanisms involved remain unclear due to the complexity of the solutions applied. In this work, the influence of some commoncations (i.e., Na+, K+, Ca²⁺ and Mg²⁺) with sulfate(SO4²⁻) anions on molybdenite flotability was investigated in the absence of flotation reagents (i.e., frothers and collectors) at pH 10. Flotation results indicated a greater depression of molybdenite recovery with increased sulfate salt concentration. The underlying mechanisms responsible for the deleterious effects in the presence of Na+ and K+ can be attributed to the increased repulsive forces between molybdenite particles and bubbles owing to increased molybdenite oxidation to produce e.g., MoO4²⁻ and HMoO4⁻. However, the increased depression observed in the presence of Mg²⁺ and Ca²⁺ is likely due to the adsorption of precipitated Mg(OH)₂ and CaMoO₄, respectively, onto molybdenite surfaces. These clearly show the different depressing mechanisms due to monovalent and divalent sulfates on molybdenite flotation in the absence of flotation reagents, to reveal the influence of these sulfate salts on its natural flotability. Refereed/Peer-reviewed

In order to minimize fresh water usage, much attention has been paid to the flotation using saline or sea water. However, the effects of various ions in these waters on froth properties in flotation are not fully understood. In this study, the effects of electrolyte solutions containing NaCl, KCl, CaCl2, and MgCl2 at different concentrations in the presence of terpenic oil as a frother were investigated on froth performance, dynamic froth stability (DFS). It was found that KCl had the best synergistic effects with terpenic oil in reducing the solution surface tension. In the presence of terpenic oil, the DFS and half-life time were reduced with the increased ion concentration. Dynamics foamability index measurements (DFI) confirmed that the increased ion concentration increased the foamability, as frother did. In addition, Gibbs adsorption isotherm suggested that the amount of terpenic oil adsorbed at the gas-liquid interface was increased with the increased ion concentration. This study therefore indicated that the presence of ions can reduce the froth stability but not decline foamability due to terpenic oil, enlighting the application of saline or sea water in defoaming process in flotation. Refereed/Peer-reviewed

Sea water has been used in flotation plants, showing a promising way to save fresh water usage. Previous studies indicated that divalent salts in sea water played negative roles in chalcopyrite flotation, but not much work have been conducted to understand the eliminating mechanisms. This study systematically investigated the effects of divalent cations of Ca2+ and Mg2+ on natural flotability of chalcopyrite in the absence of collectors and frothers. The reduced recovery was mainly due to the adsorption of Mg and Ca hydroxyl complexes and precipitation on chalcopyrite surfaces, giving rise to a less hydrophobic surface. The addition of sodium hexametaphosphate (SHMP), however, significantly improved chalcopyrite recovery. Species calculation, contact angle, zeta potential, FTIR and XPS analyses were conducted to understand the influencing mechanisms of divalent ions and the beneficial effects of SHMP on chalcopyrite recovery. The primary mechanism was that SHMP prevented the adsorption of positively charged Mg and Ca compounds or precipitation with hydrophilic properties such as Mg(OH)2 on chalcopyrite surfaces, confirmed by the Derjguin-Landau-Verwey-Overbeek (DLVO) theory. Secondly, SHMP reacted with Mg2+ and Ca2+ to form dissolvable complexes, thereby declining the formation of insoluble Mg2+ and Ca2+ compounds or precipitation. Refereed/Peer-reviewed

Chalcopyrite leaching process is hindered predominantly due to the passivation layers formed on its surface. The impurity salts normally present in the leaching systems may influence chalcopyrite leaching process. In this work, density functional theory (DFT) was carried out to investigate the influence of Mg 2+ and Ca 2+ on chalcopyrite (0 0 1)-S surface using Materials Studio. The results indicated that the presence of CaSO 4 contributed to the breakage of S–S bonds on chalcopyrite (0 0 1)-S surface. Although Ca 2+ was not found to bond with any of the S atoms derived from broken S 2 2− bond, a stable structure of Ca–SO 4 –Fe was formed. Similarly, the adsorption of MgSO 4 on chalcopyrite (0 0 1)-S surface contributed to the breakage of S 2 2− bond, forming a complex and stable structure of S–Mg–SO 4 –Fe as new passivation layers due to the bonding effects between Mg 2+ and a S atom from the broken S 2 2− bond. The formation of these new structures covered on chalcopyrite (0 0 1)-S surface, further reducing chalcopyrite leaching rates. This study, therefore for the first time, reveals the influencing mechanisms of Mg 2+ and Ca 2+ sulfates on chalcopyrite leaching at an atomic level.

Seawater has been considered as an alternative to freshwater for flotation. However, many ions in seawater were reported to depress molybdenite (MoS2), with the depressing mechanisms being insufficiently understood. In this study, the influence of divalent ions (e.g., Ca2+ and Mg2+) and dispersant on MoS2 flotation was systematically investigated. It was found that the detrimental effects of Ca2+ and Mg2+ on the natural flotability of MoS2 were mainly due to the attachment of formed CaMoO4 precipitates and Mg(OH)2 colloids onto MoS2 surface. However, the addition of sodium hexametaphosphate (SHMP) reduced the negative effects. Various measurements, including contact angle, zeta potential, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), were conducted to understand the influencing mechanisms of divalent ions and the beneficial effects of SHMP on MoS2 flotation. In addition, the Extended Derjguin&ndash, Landau&ndash, Verwey&ndash, Overbeek (EDLVO) theory was applied to investigate the total interaction energy between MoS2 particles and formed colloids, revealing that the reduced attraction force between MoS2 and Mg(OH)2 colloids in the presence of SHMP primarily resulted in the increased MoS2 recovery. In addition, SHMP combined with Mg2+ and Ca2+ to form dissolvable complexes, thereby reducing insoluble Mg2+ and Ca2+ compounds or precipitation. Thus, this study demonstrated for the first time two influencing mechanisms of SHMP in improving MoS2 recovery in the presence of Ca2+ and Mg2+.

Hydrometallurgical processing of chalcopyrite is hindered predominantly due to the passivation layers formed on the chalcopyrite surface. However, the effects of impurity cations released from the gangue are not yet well understood. Density functional theory (DFT) calculations were carried out to investigate monovalent cations of Na+ and K+ on chalcopyrite (001)-S surface using Materials Studio. The results show that the 3d orbital of Fe and 3p orbital of S predominantly contribute to their activities during chalcopyrite oxidation and dissolution processes. In addition, SO42- is more likely to be adsorbed on one Fe site in the presence of Na+, while it is preferentially adsorbed on two Fe sites in the presence of K+. However, the adsorption of both Na2SO4 and K2SO4 on the chalcopyrite (001)-S surface contributes to the breakage of S-S bonds, indicating that the impurity cations of Na+ and K+ are beneficial to chalcopyrite leaching in a sulfuric environment. The adsorption energy and partial density of states (PDOS) analyses further indicate that the adsorption of Na2SO4 on chalcopyrite (001)-S surface is favored in both -BB (bidentate binuclear) and -BM (bidentate mononuclear) modes, compared to the adsorption of K2SO4. Refereed/Peer-reviewed