Ultrasonic assisted direct contact membrane distillation hybrid process for membrane scaling mitigation

Abstract

• Ultrasonic assisted membrane distillation hybrid process was designed.• The effect of ultrasonic irradiation on membrane scaling was investigated.• Ultrasonic irradiation can effectively mitigate CaSO 4 membrane scaling.• CaCO 3 had little effect on permeability with or without ultrasonic irradiation.• Ultrasonic irradiation can restrain silica colloid deposit and maintain flux. G R A P H I C A L A B S T R A C Ta b s t r a c t a r t i c l e i n f o A novel ultrasonic assisted direct contact membrane distillation hybrid process was designed and the effect of ultrasonic irradiation on membrane scaling mitigation during membrane distillation process was investigated. Under ultrasonic irradiation, ultrasonic wave refreshed the liquid-membrane interface continuously and reduced concentration polarization in the boundary layer adjacent to membrane surface simultaneously. Therefore, ultrasonic irradiation could mitigate membrane scaling caused by CaSO 4 and prevented the permeate flux decline. Although the ultrasonic irradiation could restrain the crystal size of CaCO 3 deposits and clean membrane surface, the experimental results demonstrated that it was not necessary to introduce ultrasonic irradiation into membrane distillation process for CaCO 3 membrane scaling mitigation. Due to fast precipitation rate, the concentration of CaCO 3 solution would not cause notable permeate flux decline in the absence of ultrasonic irradiation. There would be a gradual permeate flux decline during the concentration process of silica solution because of the formation and deposition of colloidal polysilicic acid on membrane surface. The ultrasonic irradiation caused the zeta potential of silica colloids to approach neutral and enhanced the tendency of colloid deposit, but the membrane surface could be effectively kept clean and the permeate flux was hardly affected by concentration factor increasing.

Ultrasonic-assisted removal of inorganic scales in high-salinity wastewater treatment using membrane distillation

“…12c). The mitigation of fouling due to membrane scaling was also found in previous study [33] but it was applied only during the MD operation.…”

“…However, ultrasound must be used carefully because it may damage the membranes [30,31]. Ultrasonic irradiation has been used for cleaning of microfiltration (MF) and ultrafiltration (UF) membranes and found to be cost-effective [23,24,27,[32][33][34][35]. However, relatively little information is available on the effectiveness of ultrasonic-assisted cleaning technique for MD membranes [36].…”

The use of ultrasound to mitigate membrane fouling in desalination and water treatment

“…Ultrasound can also mitigate calcium sulfate and silica colloid fouling in the MD process. In a study by Hou et al [109] on direct contact MD, the ratio of flux to initial flux was maintained at 93% and 97% in case of calcium sulfate and silica fouling, respectively, due to the shock waves and microstreaming produced by the ultrasound. In addition, ultrasound can also enhance the flux by reducing the temperature polarization in the MD process [111,112].…”

Seawater desalination using air gap membrane distillation-an experimental study on membrane scaling and cleaning

“…As a result, repetitive membrane scaling and cleaning in AGMD of seawater will inevitably lead to deterioration in process performance. In this context, effective scaling prevention techniques, including but are not limited to anti-scalant addition [14 -16], utilization of ultrasonic and gas bubbling [17,18], or process optimization [9,19,20], are highly recommended.…”