Abstract: With the development of modern industry, waste mineral processing, metallurgy, chemical industry, electroplating and other industries often leads to emissions of heavy metals in soil and water contamination. Hg, Cd, Pb, Cr, As, which are biotoxic, and heavy metal pollutants such as Zn, Cu, Co, Ni, which are toxic, cannot be biodegraded, tend to be enriched in living organisms, causing various diseases and environment. Causes serious harm. Traditional techniques for controlling heavy metal pollution include chemical precipitation, permeable membranes, ion exchange, and activated carbon adsorption, but these methods are generally costly. The use of mineral materials derived from geological surface and mine waste, which are low in price and easy to process, is used to treat heavy metal pollution. It has the advantages of wide material source, low cost, high energy saving and high removal rate, and is attracting extensive attention from environmental engineering circles at home and abroad. 1.1 Surface area The purification of heavy metal contaminants by mineral materials includes the adsorption of minerals and the surface reactions of minerals and heavy metals. Based on the adsorption and surface reactions of mineral surfaces, the migration and transformation of heavy metals in soil and water can be realized, and heavy metal pollution can be effectively prevented. Mineral materials play a unique role in the field of heavy metal pollution control and environmental remediation. The development of a wide variety of natural mineral materials with abundant reserves and the rational modification of natural mineral materials with certain purification functions are new ways to control heavy metal pollution. The method has the advantages of simple equipment, simple operation and small secondary pollution. With the deepening of people's understanding of the mechanism of mineral purification, the continuous development and application of processing methods and technologies for mineral materials, and the continuous exploration of technological transformation and industrialization processes, the practical application level of mineral materials in environmental protection will continue to increase.
Construction hoist is vertical transport machinery driving by pinion and rack, mainly used on construction site for transportation of personal and materials. As a permanent or sub-permanent external elevator, it also applies to store house, dock, high tower, high chimney, etc.
There are single cage and double cages hoist. According to the need gets rid of one cage of double cages the hoist will be changed to single cage hoist. SC Construction Hoist is equipped with reliable electrical and mechanical safety device. It is efficient and safety vertical transporting equipment.
BQ supplying all kinds of construction hoist spare parts, including Construction Hoist Mast Section, Passenger Hoist Cage, Construction Hoist Anchorage Frame, Anti Fall Safety Device, Construction Hoist Overload Protector, Construction Hoist Reducer, Sliding Contact Line, Construction Hoist Motor, Passenger Hoist Rope Pulley, Construction Hoist Roller, Electromagnet Brake, etc.
Construction Hoist Spare Parts,Passenger Hoist Rope Pulley,Construction Hoist Roller,Electromagnet Brake,Spare Parts Counter Roller SHEN YANG BAOQUAN BUSINESS CO., LTD , https://www.sysuspendedplatform.com 1 structural characteristics of mineral materials
The surface of a mineral material usually refers to the interface between minerals and the atmosphere, minerals and liquids, or two solid minerals. The larger the specific surface area of ​​the mineral, the stronger the adsorption capacity. The surface of natural minerals is extremely rough, with a large specific surface area and a high surface free energy. By mechanical crushing or chemical treatment, the particle size of the mineral can be reduced and the specific surface area can be increased. Many layered, caged minerals easily reach high specific surface area under the same volume, which is beneficial to remove harmful substances in soil and water by surface adsorption.
1.2 Channel Structure <br> Many mineral materials have a pore structure. The space network structure of zeolite is filled with cavities and pores. The pores constructed by SiO and AlO tetrahedron are filled with cations such as Na and Ca. They are weakly connected with SiAl backbone and can be replaced by other cations without destroying the crystal. grid. The pores in the crystal structure of the manganese ore are constructed of MnO octahedron and filled with K+ or the like, and the pore size is close to that of the zeolite.
Common feldspar minerals also have a good pore structure, and the pore size allows water molecules to pass. Pyrolusite, apatite, tourmaline, serpentine, and vermiculite are a mineral having a pore structure. The main component of clay minerals is a layered silicate mineral with a small particle size. It has a two-dimensional grid-like SiO tetrahedral skeleton. The tetrahedral and octahedral sheets form a structural unit layer by sharing active oxygen, sometimes Na. The cations such as K and Ca are filled in the interstices between the unit layers, that is, in the interlayer region. Parallel fiber tunnel pores in sepiolite and palygorskite account for more than half of the fiber volume, and the internal surface area is considerable.
1.3 Surface activity <br> Mineral materials have strong surface activity. Since the lattice plane of the mineral surface is suddenly cut off, it is easy to produce a polar surface with excessive charge density, and the polar surface easily reacts with molecules or ions in a medium such as air or water to form a stable isolated surface.
Almost all oxide and silicate minerals undergo hydroxylation reactions when they come into contact with water to form a surface site where protonation or surface ionization can occur, thereby coordinating with other inorganic ions or with complex ions. A coordination reaction occurs. The ionization reaction on the surface of the mineral forms a proton charge, and the coordination reaction produces a surface coordinating charge. The unequal exchange of atoms in some mineral skeleton structures also produces a constant charge with ion exchange function, which will make the mineral The surface is charged. Some minerals have a "naked" metal surface that forms an acid accepting electron's acid position. It often combines with water molecules to form a proton-providing Bronsted acid site. Salt minerals and sulfide minerals also have a base on the surface which can be dissociated or polymerized in solution. The hydroxylation, chargeability, Lewis acid sites and Bronsted acid sites that occur on the surface of the mineral cause the surface phase to be different from the internal ones, giving the minerals a strong surface activity. 2 purification of mineral materials
2.1 adsorption
Adsorption is the most common and main retention mechanism for heavy metals. Adsorption includes surface adsorption and ion exchange adsorption. Surface adsorption is the enrichment of matter on the surface, and the surface adsorption of mineral materials is closely related to its surface properties. Minerals that are normally exposed to the air oxidize or carbonize rapidly, and minerals in water tend to form variable charge surfaces, which tend to increase the surface adsorption activity of minerals. In addition, the large external surface area of ​​the mineral material, the large internal surface area in the pores and the complex micromorphology also contribute to surface adsorption, thereby reducing heavy metal contaminants in the environment.
Ion exchange adsorption is a phenomenon in which the analogous image substitution causes the mineral to form a permanent charge, which is a phenomenon of balancing the charge ions in the environment. Ion exchange adsorption can occur on the surface of the mineral material, in the pores and in the interlayer domains. The Ca 2+ energy in the lattice of the apatite surface is widely exchanged and adsorbed with Pb 2+ , Cd 2+ , Hg 2+ , Zn 2+ , etc., thereby removing heavy metal ions. The Na + , K + , Ca 2+ and the like in the pores of the natural zeolite have high exchange selectivity, and the smaller the hydrated ionic radius, the easier the ions enter the zeolite grid for ion exchange. The interlaminar domains of clay minerals have a large amount of negative charge and strong ion exchange adsorption for heavy metal ions.
2.2 Surface reaction
The ability and type of mineral surface to react with molecules or ions in the medium is determined by the surface properties of the mineral and the chemical nature of the reactants. The surface coordination reaction of the hydroxylated surface with ions in the solution by electrostatic interaction is a common surface reaction. For example, Pb 2+ can coordinate with the surface of kaolinite, and Cu, Zn, Ni plasma can be matched with the quartz surface. Body or dual ligand morphological binding.
The bases S 2- and S 2 2- on the surface of sulfide minerals have a tendency to give electrons, and the surface reduction ability is strong. The surface redox reaction and its precipitation conversion, some high-priced heavy metal ions CrO 2 4 , AsO 3 4- etc. converts the sulfur on the surface of the sulfide into elemental S or S 2 O 2 3- , SO 2 4- which can enter the solution , and is itself reduced and precipitated on the surface of the mineral. When contacted with a carboxyl group, a carbonyl group, an amine group or the like in a natural organic matter, the Lewis acid site on the surface of the mineral also reacts with a heavy metal ion in the solution to form a plurality of ternary complexes. 3 purification mechanism of heavy metal pollution by mineral materials
3.1 Clay minerals <br> Clay minerals have high dispersion and large specific surface area up to 800 m 2 / g, and the gap between structural unit layers is large. The interlayer domains have a net negative charge structure property, which is easy to occur with heavy metal ions. Exchange adsorption. Due to the presence of hydroxyl groups in the outer layer of the structural unit, the bond force between the unit layers is weak, and heavy metal ions can enter the interlayer to cooperate with the hydroxyl groups. Therefore, the adsorption of heavy metals by clay minerals is mainly carried out in the form of complexation of heavy metal ions with hydroxyl groups. The adsorption selectivity of heavy metal ions is affected by the layer charge distribution of minerals, the heat of hydration of heavy metal ions, the electricity price, the ionic radius and Control of factors such as effective ionic radius. Generally, the higher the electricity price of heavy metal ions, the smaller the radius and the stronger the adsorption between clay minerals.
3.2 Salt minerals
In addition to Langmuir type and Freudlich type, the adsorption isotherms of calcite on Cu 2+ , Pb 2+ , Zn 2+ , Cd 2+ , Ni 2+ , Ag + and Cr 3+ are also expressed as adsorption amount and ion equilibrium concentration . The linear relationship and the straight line show two types of mutations at the highest ion concentration, indicating that the effect of calcite on heavy metal ions is a surface reaction involving multiple modes. The main mechanism is surface adsorption and surface precipitation.
Calcite can be used to immobilize toxic ions on calcium carbonate according to this mechanism, thereby reducing the bioavailability of heavy metals.
Sulfide minerals have good adsorption to heavy metal ions such as Cr 2+ , Pb 2+ , Cd 2+ , Hg 2+ , etc. The surface hydroxylation and slightly soluble can change the pH value of the solution, with ion reaction or surface The redox reaction produces more sites of adsorption, resulting in different types of surface reactions with different heavy metal ions at the interface. The adsorption of heavy metals by sulfides can be divided into linear type, exponential type and Langmuir type. The surface adsorption constant is related to the pH value of the system, the ionic strength, the initial concentration of the adsorbate, the temperature, etc. The pH value affects the adsorption properties of sulfides. The most significant effect, and the response of different heavy metal ions to pH changes, can adjust the acidity to achieve the best adsorption effect on different heavy metal ions.
3.3 <br> mineral soil common oxide and iron oxide, manganese oxide fine particles, large surface area, having a surface charge characteristics associated with the pH, trace heavy metals ions can enrich soil and mineral soil particle surface The surface of the oxide film. The adsorption of heavy metals by iron oxide minerals is divided into exchange adsorption and specific adsorption.
When the pH of the system is higher than the zero point, the surface of the oxide is negatively charged, and some of the cations are usually adsorbed on the outer layer of the diffusion layer without selectively compensating for the surface charge, and exchange adsorption occurs. Due to the high zero point of iron oxide, the mineral surface is positively charged in the normal pH range, and the heavy metal ions can be directly bonded to the surface hydroxyl and hydration groups in the iron oxide coordination shell, and adsorbed to the Stern of the electric double layer. Layer, which is the main form of oxide surface adsorption, called obligate adsorption.
Iron oxide minerals have strong specific adsorption and fixation properties for heavy metals, and the specific adsorption of heavy metal ions is not easy to migrate in soil or other environments. 4 Conclusion