表面活性剂用量对有机膨润土稳定性的影响

The effect of cetyltrimethylammonium bromide dosage on the stability of organobentonite

为研究有机膨润土的稳定性,通过添加不同用量的表面活性剂(十六烷基三甲基溴化铵)对有机膨润土进行改性处理。将制成的有机膨润土加入清水中,通过不同振荡时间、振荡强度、超声处理时间、温度、pH值及不同浓度盐溶液的处理后,测定离心得到的上清液中总有机碳(TOC)的含量。结果表明,相同处理条件下(超声处理除外),有机膨润土的稳定性均随着改性时表面活性剂用量的增加而逐渐降低。当表面活性剂用量小于或等于膨润土阳离子交换量(CEC)时,制备的有机膨润土比较稳定。振荡时间、振荡强度及反应温度对有机膨润土稳定性的影响不明显;增加超声波处理时间、pH值过高或过低均会降低有机膨润土的稳定性;提高处理溶液中的NaCl、CaCl2浓度,可增加有机膨膨润土尤其是高表面活性剂用量的改性有机膨润土的稳定性。因此,为避免有机膨润土的二次污染,在利用表面活性剂制造有机膨润土时,应根据膨润土的阳离子交换量确定适宜的表面活性剂用量,并使溶液pH值处于中性范围。

The present paper intends to report the authors＇ experimental findings on the effects of cetyltrimethylammonium bromide （CTMAB） dosage on the stability of organobentonite. As is known, CTMAB is one of the surfactants that is usually used for producing organobentonites. A lot of researches in this field prove experimentally that adding CTMAB helps to increase the interlayer space of organobentonites, while within the interlayer the increase of the organic content helps to absorb the organic infectants with the organobentonites. However, the CTMAB absorbed by the bentonite interlayer is also likely to get released again from the layer, which is likely to cause water contamination and in turn threaten the existence of the microorganisms in the soil, for CTMAB functions as disinfectants. Therefore, what this paper is to take interest in is just how to avoid such subsequent contaminations. For our experimental purposes, we have used different dosages of CTMAB to get the synthetic organobentonites. When clean water solution is added by organobentonites and treated for different shaking durations or ultrasonic durations and intensities with pH and salt concentration. Then, the solution with organobentonite can be centrifuged with the total organic carbon （TOC） of the supernatant being determined for the stability of the organobentonite. Thus, we have found from our experiments that the stabihty of organobentonites tends to decline with the increase of the amount of cationic surfactant in same conditions. When cationic surfactant used was less than or equal to CEC of bentonite, the organic-bentonite obtained would appear quite stable. However, the organic-bentonite would be less stable on the condition that the cationic surfactant is thicker than that of bentonite. In such situations, hardly any effect could be found on the stability of organic-bentonite by changing the shaking intensity, duration or temperatures. However, ultrasonic wave, lower or higher pH of solution may help to reduce the stability of the organic bentonite. Furthermore, NaCl and CaCl2 may have a positive effect on its stability.