Superficial Modification Of Porous Ceramics Filter Media And Its Treatment Of Simulating Oil Field Produced Water Based On Coalescence Filter Mechanism

Along with the rapid development of global industry, most of the oilfields in China havecome to the late development period, oil moisture content was increased, therefore output ofthe oilfield produced water constantly enhanced. As a high pollution resource, oilfieldproduced water was complex with ingredient, high with salinity and oil content, and it woulddamage the social environment and human health if it was directly discharged withouttreatment. So, more and more researchers are exploring and studying new technique includingphysical, chemical, physical-chemical process, biochemical process and some othercombination process to treat oily wastewater. As a special physical-chemical method,coalescence was more concerned by scholars both at home and abroad because of its uniqueoil removal mechanism. As a result, developing stable, effective coalescence material andnew method was rather important. Porous ceramic filter material was a typical coarse grainedmaterial, and it has advantages such as stability, high porosity, none secondary pollution,strong regeneration, so it was widely used in oily wastewater treatment. But it was of not sohigh lipophobicity itself, and its effect of treating wastewater was not so ideality. So, it isnecessary to modify the filter material or combined with other technologies.In this paper, porous ceramic filter media was modified respectively with aluminatecoupiling agent and polyethylene glycol （PEG）, for the purpose of improving its property oflipophilicity or lipophobicity. The filter media of before and after modification weredetermined by FTIR, SEM, density, porosity and contact angle to water. Also, the effect ofdealing with simulating oily wastewater was tested when compared to its combination withmagnetic separation. The influence factors of oily wastewater treatment were investigatedthoroughly, for example, column height, filter velocity, quality of orginal wastewater, strengthof magnetic field, and so on. Main research achievements are as follows:（1） When aluminate coupiling agent was oil wet modifier and evaluation index was oilrate, the L₉（3⁴） orthogonal experiment was used to optimize the modification process oflipophilicity. The results showed that the best modification parameters included aluminatecoupling agent （5%）, temperature （90℃）, modification time （20min） and coating time （one）.The FTIR of modified porous ceramic filter media came out some characteristic adsorptionpeaks like-CH₃and-CH₂, which came from aluminate coupiling agent. The density ofmodified filter was smaller than original and pretreatment media, which was because of theoil-wet coating on the surface that closed the porosity partly. The presence of modifieroccupied part of the channel of the modified filter media, thus the porosity inside it decreased.It can be seen from SEM that the number of holes on the surface of modified media was lessand the amount of aluminum and oxygen that tested by elemental analysis was much morethan pretreatment media. The contact angle to water of modified filter media was increased by90°to pretreatment media. In a word, all the results showed that the lipophilic modification was successful. At a speed of15m/h and after20min, and oil removal rate of modified filterincreased from65.18%to96.46%compared with pretreatment filter. The breakthroughcurves showed that the modified media was more stable and efficient operation, and theefficiency was more significant.（2） Polyethylene glycol （PEG） was used to improve the lipophobicity of filter mediausing L₉（3⁴） orthogonal experiment. The results showed that: the best modification processparameters included polyethylene glycol （PEG）（3.5%, modified liquid quality score）,modification temperature （80℃）, and modification time （30min）. New-OH adsorption peakappeared at1384cm^-1and its peak at3434cm^-1was widen obviously, and-CH stretchingvibration adsorption peak appeared at2900cm^-1in FTIR of modified media, which all causedby the coating of polyethylene glycol on the media. It was measured and calculated that thedensity, porosity and contact angle to water were reduced when the porous ceramic filtermedia was modified, and its hydrophilicity was improved, but it was its too thin coating ofPEG that their changing extent was not much. The oil removal rate of the original andpretreatment was68.59%and76.52%separately, and it increased to97.00%after beingmodified. The regular of oil and turbidity removal rate with time was compared amongoriginal, pretreatment and modified filter media. The result was that, the removal rate wassignificantly improved when the media was modified, and its oil and turbidity removal ratecould remain above90%for a long time, which suggested its efficiency and stability.（3） As permanent magnetic form field, porous ceramic filter media of before and afterlipophilicity or lipophobicity modification were combined respectively with magneticseparation. And processing mode of filter media, combining ways and mass ratio of filter andferroferric oxide （Fe₃O₄）, magnetic field intensity, filter velocity, filter column height andparticle size of Fe₃O₄were discussed to weigh the effect. The original material with particlesize0.8¹.6mm was mixed equably with Fe₃O₄particle by a mass ratio of3:1, and the oiland turbidity removal rate was92.22%and91.09%respectively with column height320mm,filter speed15m/h, magnetic intensity5B0, Fe₃O₄particle size0.8¹.6mm. When the originalmaterial particle size was2.8⁴mm, and its mass ratio to Fe₃O₄was1:1with column height320mm, filter speed5m/h, magnetic intensity5B0, Fe₃O₄particle size0.8¹.6mm, then itsoil and turbidity removal rate could reach97.91%and97.70%partly. Method of breakthroughcurves was used to compare efficiency of removal rate. The ct/c0of lipophobicitymodification was0.2781（which meant oil removal rate was72.19%） while the column runcontinuously to135min, but the running time decreased to100min when it was combinedwith magnetic separation, that was, the treatment ability was reduced by35min or so. Whenthe hydrophobic oil modified filter media was combined with magnetic separation, its oilremoval efficiency could remained around98%for about175min, and the oscillationamplitude was small. The treatment efficiency with was greatly improved compared to thefilter media alone without magnetic separation, and the filter column could remain stable andefficient for a long time relatively. All the results above showed that, the removal rate of both oil and turbidity would increase when the filter media was combined with magnetic separation,expect for lipophilicity modification meida.（4） The self-made inorganic-organic composite flocculant was adopted to deal with oilfield produced water in a simple dynamic simulation equipment. In this experiment, the oilywastewater first deposited in the coagulation sedimentation tank, and then loop throughcollision coalescence filtration-magnetic separation device and wetting coalescence filtrationequipment. Compared with the independent operating experiment, the filtering speed in thiscontinuation experiment was faster, the processing water capacity was bigger, and the runningtime was longer. Importantly, the efficiency was greatly improved after combination withmagnetic separation. A series of continuous experiments were carried out to study the effectfactors of treatment, such as flocculant dosage, filter velocity, column height, and feed waterquality and so on. The figures proved that, this dynamic device could used to deal with oilywastewater with oil content was low and middle, and the effect was significant. When the oilconcentration of original wastewater was61.23mg/L, turbidity89NTU, column height400mm, filter velocity27.5m/h, magnetic intensity8B0, flocculating agent concentration1.5mg/L, and the standing time30min, the filter column could operate almost10h with its oilremoval rate80%and turbidity removal rate next to90%. Namely, the oil content andturbidity was4.91mg/L and4.03NTU separately after the wastewater was treated. As a result,the oil concentration could satisfy the A1level of “recommended injection water quality fordetrital rock oil reservoirs and analyzing methods”. So, the processing ability of this devicewas strong, and its operation cycle time is long.（5） The lipophilicity modification porous ceramic filter media was employed to treat oilfield produced wastewater mainly relied on a mechanism of wetting coalescence. Oils in thewastewater could be adsorbed and massed by the lipophilicity groups on the media, and whenthe oils got larger, they would gather to big drops and then fall off from the surface in order tosupply sufficient space to the oil droplets subsequent. The process could last till the filtermedia was saturated. At the same time, as the size of lipophilicity media was small, theinterspace among them was little, which made oils collided easily with each other except forwetting coalescence. Unlike lipophilicity filter media, the mechanism of lipophobicity wasmainly collision coalescence long with wetting coalescence. The probability of collisionbetween oil and oil was augmented based on the lipophobicity groups, and the odds of oilsgrowing up relied on collision coalescence was added, which made the oil drops beintercepted and removed easily. When the porous ceramic filter media was combined withmagnetic separation, the existence of Fe₃O₄and magnetic field played a very important role ineliminate oils in addition to its coalescence function. It was magnetic separation effect that notonly made oil layering with demulsification, but also attracted some suspended solids thatbeing magnetized by magnetic effect, thus oil droplets that adsorbed onto suspended solidswere removed. The oil removal mechanism in the self-made dynamic simulation device wasan effective combination of coalescence filtration, magnetic separation and integration of coagulation sedimentation, which greatly improved the processing efficiency of oil fieldproduced water.