At present, the methods of phosphorus removal from wastewater with chemical precipitation method, electrolytic method, microorganism method and biological method, physical adsorption method, soil treatment method and membrane technology processing method, etc.The adsorption method with its large capacity, less energy consumption, small pollution, removal of the advantages of fast and recycled, has been widely used in the phosphorus removal.The studies of phosphorus adsorption by directly with a single material is mature, are now the main direction of the research was carried out on the material used in the study of the adsorption of phosphorus, modified in adsorption of modified materials research.
　　Phosphorus removal by adsorption are research status
　　1. The activated carbon
　　In recent years the study of activated carbon for adsorption, mostly in modified form, by enhancing chemical adsorption ability of active carbon to improve the effect of phosphorus removal.
　　Iron activated carbon has a good effect on adsorption of phosphorus, compared with iron activated carbon (AC - Fe) and iron oxide activated carbon (AC/O - Fe) found that by nitric acid oxidation of activated carbon (AC)/N - Fe) capable of carrying more Fe, thus forming a large number of active site in the surface of activated carbon, the higher than AC - Fe phosphorus adsorption effect.Including AC/N - Fe Ⅱ and AC/N - Fe Ⅲ adsorption process are mainly composed of surface adsorption and diffusion in the granules, and AC/N - Fe Ⅱ than AC/N - Fe Ⅲ particle diffusion ability, the activation energy is higher, so the comprehensive research show that the AC/N - Fe Ⅱ on phosphorus adsorption effect is better than that of AC/N - Fe Ⅲ.
　　Solution of ACF - La phosphorus adsorption capacity of NO3 -, SO42 -, CO32 - and variation.ACF - LaOH adsorption of phosphorus is the main mechanism of the ligand exchange, electrostatic effect and Lewis acid-base reaction.PH increase will weaken the ligand exchange, and the ability of electrostatic interactions, and enhance the ability of Lewis acid-base reaction, fewer comprehensive adsorption quantity.The ACF - LaFe adsorption of phosphorus found that ACF - LaFe with a large number of net positive charge, make its maximum adsorption capacity higher than that of ACF - LaOH, maximum adsorption capacity at room temperature is up to 29.44 mg/g, coexisting anions have adverse effects on adsorption of phosphorus, order: F - > SO42 - > NO3 - > Cl -.
　　2. The biomass,
　　Biomass is mainly refers to the nature of all living can grow organic material.Used in the project of adsorption of organic matter and its waste is biomass adsorbent.Biomass adsorbent has the following advantages: the material of low cost, wide distribution;High porosity, large surface area.Surface layer contained more hydroxyl, simple modification, and high activity of phosphate radical ion reactions;Insoluble in water, easy separation.In recent years the research of biomass adsorbent mollusk shells, shell, bagasse, etc.
　　In research with oyster shell adsorption initial concentration of 10 mg/L of phosphorus found that when the reaction temperature rose from 20 ℃ to 30 ℃ and shell size from 590 microns to 180 microns, can increase the adsorption capacity of oyster shells, oyster shell is rich in adsorption sites, and adsorbent more environmentally friendly than most.
　　T. with calcined eggshell (CWE) adsorption of phosphorus from waste found that CWE adsorption of phosphorus removal rate at pH 2 ~ 10 can be greater than 99%, and get the best dosing adsorbent mass concentration of 2 g/L;The existence of other anions on the effects of a CWE adsorption of phosphorus, phosphorus adsorption CWE after due to contains a lot of calcium, magnesium and phosphorus, can be used as a fertilizer and soil conditioner;Attached iron hydroxide waste shell of phosphorus adsorption rate soon.
　　W. study of modified bagasse adsorption of phosphorus, found that the effect of adhesion of Fe2 + bagasse (0.06 mol/g) ratio not attached Fe2 + of bagasse in the adsorption of phosphorus efficiency increased by 45%, the concentration of carboxymethyl modified bagasse adherent Fe2 + than unmodified bagasse increased by 80%, only need to do a little bit for raw materials of chemical modification, phosphorus adsorption performance can get greatly optimized.
　　3. The metal oxide (hydrogen)
    (1).Metal oxide
    Metal oxide has a large surface area, many hydroxyl groups and choose the advantages of high adsorption.
    Iron oxide in phosphorus adsorption by electrostatic adsorption and spherical ball within complex chemical adsorption [11].Magnetic iron oxide nanoparticles in the initial mass concentration of phosphorus was 2 ~ 20 mg/L, adsorbent additive mass concentration is 0.6 g/L, the reaction time of 24 h, the maximum phosphorus adsorption capacity for 5.03 mg/g, in the pH = 11.1, adsorption capacity, fell sharply to 0.33 mg/g.
    Hydrous zirconia l. research found that when phosphorus adsorption temperature from 25 ℃ to 65 ℃, the adsorption capacity by the 53 to 67 mg/g, mg/g and in 12 h to reach adsorption equilibrium, in the pH = 12, about 74% of the phosphorus to desorption.Zirconium oxide nanoparticles of phosphorus adsorption rate soon, in the pH = 6.2 can reach maximum adsorption capacity of 99.01 mg/g, is one of the tallest adsorbent adsorption capacity, high concentrations of coexisting anions have little impact on the adsorption of phosphorus, the adsorption of the optimum pH of 2 ~ 6, adsorption capacity in pH over 7 fell sharply [14].
    (2).Hydrotalcite
    In the study of MgAl - CO3 hydrotalcite adsorption of phosphorus, it found that, when the initial concentration of phosphorus in 25 to 100 mg/L, can be reached within 30 minutes adsorption equilibrium, the phosphorus removal rate over 99%.MgAlZr - CO3 hydrotalcite on phosphorus adsorption is very high, the choice of adsorption of ions in the solution of the sort as HPO42 - > > SO42 - > Cl -, NO3 -, this is because the phosphate ions directly with interlayer Zr (Ⅳ) ion complexing reaction happened.
    Hydrotalcite adsorption of phosphorus research ZnAl - 2-300, found that the effect of sludge dewatering liquid when the temperature rose from 25 ℃ to 30 ℃, hydrotalcite phosphorus adsorption capacity increased, the water temperature to 50 ℃, hydrotalcite adsorption capacity and reduced to 25 ℃.Roasting ZnAl hydrotalcite can increase the surface area and increase the porosity, calcination temperature is 300 ℃ when the phosphorus removal effect is best, and spinel at 600 ℃ so as to reduce the surface area.
    Colloid hydrotalcite nano piece in pH 4.5 ~ 11 in phosphorus removal effect is good, after the adsorption of phosphorus of adsorbent can be used as a common growth of the algae ulva fertilizer.
    4. Silicon-based mesoporous molecular sieve
    Research of fly ash and a pot of MCM - 41 prepared, adsorption of phosphorus found in the pH = 10 MCM - 41 - the CFA - 10 has the largest gap size 0.98 cm3 / g, 1 020 m2 / g the highest specific surface area and the lowest n (Si) : n (Al), and 25 ℃ are the adsorption capacity of 64.2 mg/g, 53.5 mg/g than the SBA - 15, 31.1 mg/g of MCM - 41 and diatomite 62.7 mg/g.In the research of lanthanum 2 amino modified MCM - 41 found when phosphorus adsorption, the adsorption rate and adsorption capacity of adsorbent is very high, the maximum adsorption capacity of 54.3 mg/g, pH 3.0 ~ 7.0 for adsorption reaction optimum pH, the presence of Cl - and NO3 - in the solution of phosphorus removal effect is very small, while the existence of F - and SO42 - influence is obvious.
    J. contrast of pure, amino faculties and condensation of SBA - 15, found that the maximum adsorption capacity were 2.018, 59.890, 69.970 mg/g, adhered on the surface of the inner hole of the amino of reinforcement learning affinity is relatively pure SBA - 15 of the reason of higher adsorption capacity.
    5. Clay minerals content
    Clay minerals content is the main mineral composition of clay rock and soil.They are some of the water containing aluminum, magnesium silicate minerals, are the main ingredients of soils and sediments, its structure is characterized by a water-bearing layer structure.Often used for adsorption of clay minerals content of kaolinite, bentonite, vermiculite, attapulgite and deer bog soil, etc.
    Research by hydrochloric acid and modified calcined kaolin on phosphorus adsorption effect, found that the hydrochloric acid modified kaolin surface area increases, thus a lot of Al, Si and other active point, adsorption of phosphorus ability stronger, the mass fraction of 9% acid modified kaolin in the initial mass concentration of 20 mg/L of phosphorus adsorption of phosphorus effect best, 25 mL solution removal rate was 81.8%, 500 ℃ calcination modification of kaolin in the Al element to show the best state of activation, the removal rate of phosphorus in the solution of 99.5%.Compared with unmodified, modification and acid modified kaolinite calcined found that acid modified kaolinite is the one of the biggest phosphorus adsorption capacity, adding a small amount of kaolin can significantly reduce the phosphate solution.
    With lanthanum modified bentonite adsorption of phosphorus found in fresh water and salt water, pH of more than 8.1, the combination of the bentonite and phosphorus ability affected by larger, because the CO32 - solubility in hard water is higher, the effect more apparent in hard water.With hydrochloric acid and calcination method of modified bentonite adsorption of phosphorus research found that the phosphorus removal effect of modified bentonite increased with the increase of the acid concentration, 500 ℃ calcination of modified bentonite in initial mass concentration of phosphorus for 10 mg/L, pH = 9 for phosphorus removal rate can reach 92.77%, 0.47 mg/L residual phosphorus concentration has reached the level A of integrated wastewater discharge standard.
    Research in La (OH) 3 modified vermiculite adsorption of phosphorus found that vermiculite at 25 ℃ maximum adsorption capacity, 79.6 mg/g, 2 mg/L with the modified vermiculite secondary low concentration of phosphate processing, 10 min phosphorus removal rate can reach 97.9%, makes the mass concentration of phosphorus dropped below 50 mu g/L, in the solution F -, Cl -, NO3 -, SO42 - the existence of the phosphorus removal effect can be neglected, but 0.1 mol/L CO32 - is to make the removal rate of phosphorus decreased to 54.3%.The calcination temperature on the effect of attapulgite adsorption of phosphorus was found, in the calcining temperature of 200 ~ 900 ℃, 700 ℃ calcination of attapulgite has the maximum adsorption capacity, 5.2 mg/g.Research deer bog soil on phosphorus adsorption experiments found that the adsorption process of the top 110 min for quick response, to more than 24 h after 110 min for the slow response, maximum adsorption capacity of 2.13 mg/g, due to the adsorption of optimum pH = 6, the deer bog soil phosphorus in waste water by adsorption generally do not need to adjust pH.
    6. Other
    In addition to the above a few kinds adsorbent, iron ore, graphene and gel, etc. Also can be used as the adsorbent phosphorus.The water iron ore on phosphate adsorption experiment found that get the maximum adsorption capacity in pH = 4, 104.8 mg/g;While in the pH = 7 adsorption capacity of 77.8 mg/g.The adsorbent can be directly used in municipal sewage processing (pH 6.5 ~ 7.3), in the solution existence of Cl -, NO3 -, SO42 - will have little impact on the phosphorus removal.Research on phosphorus adsorption on the magnetite, goethite mixed phase, in the initial phosphorus concentration of 51.8 mg/L, pH = 2 congenial and magnetite, goethite and mass concentration of 10 g/L, magnetite, goethite removal rate reached 94.16% of phosphorus in the solution.In initial phosphorus mass concentration of 100 mg/L and the temperature of 30 ℃, graphene for phosphorus adsorption capacity is 89.37 mg/g (32).Gel with adsorption of Cu water without any processing directly used for adsorption of phosphorus, according to a study in the pH = 6.1 when the gel has the maximum phosphorus adsorption capacity of 87.62 mg/g, coexisting anions on the order of the phosphorus removal effect of C5H7O5COO - > SO42 - > HCO3 - > Cl - > NO3 -, the first two, the latter two.
　　conclusion
    Phosphorus removal by adsorption are compared to other phosphorus removal technology has a large capacity, less energy consumption, small pollution, quick removal and the advantages of the recycled, but there are also many shortcomings of its own: coexistence ions has significant effects on the modified activated carbon and phosphorus;Biomass adsorption capacity is small;The change of pH had a great influence on metal oxide adsorption capacity;Several specific anion effect on silicon-based mesoporous molecular sieve;Clay minerals content widespread adsorption capacity of small defects.
    Therefore, in the later study, the phosphorus removal by adsorption are mainly to delve into several aspects:
    (1).To take into account the above disadvantages to choose the appropriate modification;
    (2).On the adsorption of modified principle of research, the current research focus on removal efficiency, lack of system theory and model for describing the principle and process of phosphorus;
    (3).Research on adsorbent of subsequent processing, does not pay attention to the subsequent processing after the adsorption of phosphorus, often can cause secondary pollution, is not conducive to environmental protection, can put the waste development for plant fertilizer or soil conditioner, etc.With the development of adsorbent modified and theoretical research thorough, adsorption method in wastewater phosphorus removal and control eutrophication of water body is bound to play an important role.