Preparation Of Porous Functional Materials Based On Sludge And Geopolymers And Research On Sewage Purification Performance

Water eutrophication has become a global problem due to it not only poses a major threat to the ecological environment,but also threatens human health,economic and social sustainable development.Excessive phosphorus content is an important reason for the water eutrophication.Therefore,seeking environmentally friendly materials to achieve efficient recycling of phosphorus-containing sludge and purificating of phosphorus-containing sewage has become a research hotspot.Geopolymers have advantages such as naturally available,environmentally friendly,low cost,easy to recycle,and non-toxic.The geopolymer-based porous materials for the treatment of phosphorus-containing sewage is an important path prepared through modification and loading of different elements,which is endowed with high adsorption and excellent mechanical properties.Phosphorus-containing sludge also has the elemental composition and structural characteristics of geopolymers,and can be recycled into a catalyst for the degradation of organic pollutants.It not only realizes the recycling and utilization of phosphorus-containing sludge,but also can be used to remove organic pollutants in wastewater.In this paper,5S@Fe-500,HCK@Zr,and Fe Mn/K-400 nanocomposite materials were synthesized using geopolymer sludge and kaolin as carriers,respectively.By recycling phosphorus-containing sludge,adsorbing inorganic phosphorus and activating peroxymonosulfate(PMS)to degrade organic phosphorus in phosphorus-containing sewage,the recycling of phosphorus-containing sludge and purification of phosphorus-containing sewage were realized.The contents are mainly divided into the following three parts:(1)Sludge-based biochar material loaded with nano-Fe₃O₄(x S@Fe-y)was fabricated via hydrothermal carbonization process and employed as catalyst to activate PMS for degrading organic dyes in wastewater.Benefiting from the proper iron content,porous structure and the good dispersibility of nano-Fe₃O₄ on the catalyst surface,the proposed 5S@Fe-500 catalyst not only exhibited excellent catalytic activity and durability in the activation of PMS to degrade Rhodamine B(Rh B),which was almost completely removed in 10 min(50 m L 50mg·L^-1Rh B),but also performed broad application prospects in pollutant degradation,such as Methylene blue(MB)and Congo red.The free radical quenching test and electron spin-resonance spectroscopy(ESR)detection demonstrated that O₂·^-,SO₄·^-,·OH and ¹O₂were generated during the process of catalyst activation of PMS.Based on this,a possible reaction pathway for degrading Rh B with the aid of 5S@Fe-500 was put forward.It is believed that this work offers a promising reuse method of converting the waste phosphorus-containing sludge to a high efficiency and low-cost nano magnetic catalyst to activate PMS for degrading refractory organic pollutants in aquatic surroundings.(2)Kaolin was successively modified by means of calcination,acidization,pore-forming and Zr doping to prepare HCK@Zr adsorbent with high selective adsorption effect on phosphate.The characterization results showed that the Zr-doped three-dimensional porous modified kaolin adsorbent with relatively large specific surface area was successfully prepared,and Zr was uniformly dispersed on the surface of HCK@Zr.Adsorption experiments illustrated that HCK@Zr had the best adsorption effect on PO₄^3-when the p H was 10 and the addition amount of Zr O(NO₃)₂ was 50%(m _Zr/m_total)during the synthesis,and the adsorption capacity was up to 12.43 mg·g^-1.The adsorption behavior was in accordance with the pseudo-second order kinetic and Frenudlich adsorption model.In addition,HCK@Zr has a good selective adsorption performance for PO₄^3-when both Cl^-and SO₄^2-exist.HCK@Zr adsorbent is chemically stable,economical and pollution-free,with highly selective adsorption of phosphate and excellent reusability,which is expected to be applied in the treatment of phosphorus-containing sewage and phosphorus recovery.(3)Kaolin was used as the three-dimensional framework,and Fe Mn/K catalyst was prepared by growing Fe Mn binary oxide on the kaolin framework by hydrothermal and redox methods.PMS was activated to realize the degradation of Bis(p-nitrophenyl)phosphate(BNPP).The experimental results showed that the degradation efficiency of Fe Mn/K-400catalyst for the BNPP solution with a concentration of 10 mg·L^-1 was as high as 97.81%in360 min,and it exhibited excellent reusability in four rounds of cyclic degradation experiments.In addition,the catalytic activity of Fe Mn/K-400 catalyst was higher than that of Fe Mn-400,and the ESR test showed the content of O₂·^-,SO₄·^-and·OH radicals in Fe Mn/K-400/PMS system are higher than that in Fe Mn-400/PMS system,which was due to the fact that the skeleton structure of kaolin changed the electronic structure of the elements in the Fe Mn binary oxide and increased the ratio of adsorbed oxygen species and Fe²⁺in the catalyst,thereby enhancing the reaction activity of the catalyst to PMS.