Study On The Remediation Of Iron-manganese Contaminated Groundwater By Insoluble Humic Acid/Tourmaline Composite Particles

Iron-manganese groundwater exists widely throughout our country,and how to economically and efficiently repair the iron-manganese groundwater has become the focus.In view of this background,the preparation of new adsorption materials for removing iron and manganese is the key to research and application.This article selects the combination of inorganic compound tourmaline（TM）and natural organic polymer humic acid（HA）,which is carbonized at 330°C to convert the humic acid into insoluble humic acid（IHA）,and adding the modification reagent natural polymer starch,prepared insoluble humic acid/tourmaline composite particles（TM/IHA）,the specific research results are as follows:（1）Through single factor experiments and orthogonal experiments,the best conditions for iron and manganese removal by tourmaline were determined,and adsorption isotherm models and adsorption kinetic models were established.Microscopic characterizations such as XRD,FTIR,SEM and EDS reveal the mechanism of iron and manganese removal.The result shows:the optimal conditions for treating 100 ml of composite water sample with Fe²⁺content of 25mg/L and Mn²⁺content of 10 mg/L for tourmaline are:iron tourmaline particle size is 300 mesh,dosage is 15 g/L,reaction time 240 min,p H 6,The reaction temperature is 35°C,at this time,the removal rates of Fe²⁺and Mn²⁺are 99.25%and 94.89%,respectively.TM can buffer the p H of the solution to make the p H after the reaction reach neutral.Through orthogonal test analysis,the influence order of tourmaline adsorption on Fe²⁺and Mn²⁺is:dosage of tourmaline>p H value>reaction time.The adsorption of Fe²⁺and Mn²⁺by TM was in accordance with the pseudo second order kinetic model and Langmuir model.The results of microscopic characterization show that TM is composed of Na Fe₃Al₆（BO₃）₃Si O₆O₁₈（OH）₄,and the surface agglomeration is serious,the pore distribution is uneven,and it has the characteristics of small particle size and large specific surface area.The adsorption of Fe²⁺and Mn²⁺in groundwater is coexisted by physical adsorption and chemical adsorption.The study found that TM is very easy to agglomerate and is difficult to separate from water,and the Mn²⁺effluent does not meet the discharge standard,so it cannot be directly applied to repair the groundwater contaminated by iron and manganese,and a suitable carrier should be selected for modification.（2）Through single factor experiments,the best TM/IHA composite particles prepared under the conditions of tourmaline and insoluble humic acid mixing ratio,mixing time,calcination temperature and calcination time are studied.The result shows:the best preparation conditions for TM/IHA composite particles are:dissolve the pretreated HA in 0.1 mol/L Na OH,then add tourmaline powder at the ratio of TM:HA=2:3,adjust the p H to 6.0,and then The mixture is placed in a shaker（30°C,150 r/min）and shaken for 18 hours,and the precipitate is collected,and then washed with deionized water.The wet solid material is dried in an oven at60-70°C,ground and sieved,and then added to 95°C Gelatinized etherified starch（1/10）was mixed to form adsorbent particles with a particle size of 3-5 mm,which were calcined in a muffle furnace at 330°C for 90 min to form TM/IHA composite particles.（3）Through single factor test and response surface test,the best conditions for iron and manganese removal by tourmaline were determined,and the desorption and reusability of TM/IHA were discussed.The mechanism of simultaneous removal of iron and manganese is revealed through adsorption isotherm model,kinetic model and microscopic characterization.The result shows:the optimal conditions for TM/IHA composite particles to treat 100ml of Fe²⁺content 25 mg/L and Mn²⁺content 10 mg/L composite water sample are:TM/IHA dosage 10 g/L,p H 6,reaction time 240 min,temperature 35°C,the speed is 150 r/min,and the removal rates of Fe²⁺and Mn²⁺are 99.98%and 99.65%,respectively.After five cycles of regeneration,the removal rate of Fe²⁺and Mn²⁺is reduced by about 10%.TM/IHA has good reusable performance and has great potential for removing metals in water.Through the RSM test design,the single-factor influence on Fe²⁺and Mn²⁺was obtained as dosage>p H>reaction time,and the absolute error between the predicted value and the test value was verified by the verification test to be 0.05%and 0.13%,both lower than 5%,confirming that the test model is reliable.The adsorption process conforms to the Langmuir model and the quasi second order kinetic model,and the intra particle diffusion is not the only rate limiting step in the adsorption process.The adsorption process of Fe²⁺and Mn²⁺by TM/IHA is spontaneous,endothermic,and sustainable,and tends to be single-layer adsorption.Through XRD,FTIR,BET and SEM-EDS analysis,it is confirmed that the TM/IHA composite particles are mainly composed of C,O,H,N,Al,Si,B and other elements,retaining the crystal structure of the raw material,and the surface is rich in silicon and oxygen,alkyl and silanol groups.Studies have shown that physical adsorption,surface coordination adsorption,chemical precipitation,and ion exchange are the main interaction mechanisms for TM/IHA to adsorb Fe²⁺and Mn²⁺.（4）Through dynamic experiments,the removal effect of TM/IHA on iron and manganese was determined under the conditions of different adsorbent filling quality,different flow rate,and different influent concentration.The result shows:the penetration curve of TM/IHA composite particles for Fe²⁺and Mn²⁺ions is affected by the bed height,flow rate and influent concentration.Reducing the flow rate and influent concentration and increasing the bed height will prolong the operation time of the dynamic column.If the bed height is too low,the penetration point has not reached the expected treatment effect.When the bed height is too high,not only the removal efficiency of Fe²⁺and Mn²⁺is slow,but also the utilization rate of the adsorbent is reduced.If the flow rate is too low,it is easy to cause longitudinal back-mixing in the column.When the flow rate is too large,the Fe²⁺and Mn²⁺ions pass through the adsorption layer faster,resulting in a decrease in the total amount of adsorption.The increase of influent concentration not only reduces the removal rate,but also greatly shortens the total operating time of the dynamic column,and reduces the amount of treated water.Therefore,the bed height,flow rate and influent concentration should be determined on the basis of ensuring a certain adsorption capacity,taking into account factors such as column length and column diameter.Moreover,the dynamic adsorption process of Fe²⁺and Mn²⁺by TM/IHA is more suitable for fitting with Yoon-Nelson model.This thesis contains 70 pictures,26 tables,and 100 references.