Preparation Of Iron Pillared Rectorites And Their Simultaneous Removal Mechanism Of Heavy Metals And Organic Pollutants

With the acceleration of industrialization,the problem of combined pollution in water caused by heavy metals and organics is becoming more and more serious.The long-term exposure and accumulation of heavy metals and organic pollutants not only aggravate the risk of water quality deterioration,but also seriously increase the difficulty of treatment.The traditional process is usually treated in sections.This method has the disadvantages of long operating time,high cost,complex operation and easy to cause secondary pollution.In recent years,developing technology to simultaneous remove heavy metal-organics combined pollution has become a hot spot in environment field.In order to solve the problems of low reaction efficiency,weak catalytic stability and high cost,a novel heterogeneous Fenton simultaneous removal system based on iron-pillared rectorite catalyst was constructed from the design and synthesis of cheap and efficient catalyst.The influence of different organic pollutants on heavy metal ions reduction by heterogeneous Fenton was studied from the molecular structure level.Based on the intermediate products during heterogeneous Fenton degradation process,the interactive removal way of heavy metals and organic pollutants was revealed.Moreover,the synchronous oxidation-reduction mechanism of organic pollutants and heavy metals was studied in depth,and the mechanism of simultaneous oxidation-reduction of organic pollutants and heavy metals was studied.It will provide theoretical basis for heterogeneous Fenton system to treat combined pollutants in water.The main work is summarized as follows:（1）Iron-pillared rectorite catalysts（Fe-R-2）were prepared in situ by using Rhodamine B（Rh B）to induce iron during Fenton oxidation process.The preparation method takes the secondary waste iron-mud as the iron source and cheap rectorite as the carrier,which can significantly reduce the preparation cost.The characterization results showed that Fe OOH was the main form of iron active species.Although Rh B was completely degraded in the preparation process,more Fe OOH entered into the rectorite layer due to the induction of Rh B,which on the one hand led to the increase of the layer spacing,on the other hand led to the increase of mesopores.In addition,the introduction of Rh B in the preparation process can significantly improve the conductivity and electron transfer ability.（2）Fe-R-2 catalyst was used in heterogeneous Fenton system to degrade organic pollutants in water.Taking Tetracycline hydrochloride（TC）as a target pollutant.Under the same conditions,the degradation activity of Fe-R-2 is 2.34 times of that of Fe-R-0 which obtained without Rh B during preparation.Under the condition of 0.2 g/L catalyst and 10m M H₂O₂,TC（initial concentration of 100 mg/L）could be completely degraded within 60min.Fe-R-2 catalyst could maintain the degradation performance in a wide p H range（3.60-9.06）.Additionally,the activity of Fe-R-2 did not decrease significantly after 5 cycles.Fe-R-2 also showed excellent catalytic degradation ability toward Rh B and Acid Red G（ARG）.The mechanism study indicated that·OH radical played an important role in TC degradation.（3）Based on the excellent catalytic ability of Fe-R-2,a combined pollution system was constructed by adding heavy metals into a single organic pollutant system,and the simultaneous oxidation-reduction ability of Fe-R-2 toward the combined pollution was investigated.Cr（Ⅵ）and TC were selected as research object.The results reveal that the presence of TC increased the Cr（Ⅵ）reduction rate 47.4-fold in the Fe-R-2/H₂O₂/LED system owing to the generation of reductive intermediates which effectively reduce Cr（Ⅵ）to Cr（III）,while consuming hydroxyl radicals and suppressing the reoxidation of Cr（III）.Under LED light radiation,Fe-R-2 can catalyze H₂O₂to simultaneous removal of Cr（Ⅵ）and TC with high efficiency.The reduction rate and degradation rate are 98.1%and 97.5%respectively within 150 min,and the COD removal rate reach up to 80%.Moreover,Fe-R-2catalyst can operate efficiently in a wide p H range（3.81-8.01）,and still has a good catalytic activity after 5 cycles.It is worth noting that Fe-R-2 has better performance under actual sunlight radiation than LED.Fe-R-2/H₂O₂/LED system also shows excellent activity in simultaneously removing Cr（Ⅵ）and other pollutants such as Rh B and ARG.This work may shed light on the design of green,efficient and recyclable heterogeneous catalysts,and advance the practical utility of heterogeneous Fenton-like process for combined contaminants remediation.