Optimization and scale-up of a new photobleaching agar extraction process from Gracilaria lemaneiformis

An eco-friendly photobleaching extraction process for agar extraction from the red alga Gracilaria lemaneiformis was developed for the benefit of workers' health and environmental safety. Here we report the optimization of key process parameters (alkali modification concentration, photobleaching duration, algal length and screen filter opening size) in order to scale up this new technique. The optimal conditions were found to be modification by 3-5% NaOH, photobleaching for 5 h, using algal fragments 2 -4 cm in length, and a filter screen with a 6 mu m opening. A 20-L agar extraction reactor was thus constructed, and the scale-up of the agar extraction process was tested in six batch experiments. The resulting agar quality was similar to that of the laboratory-scale extraction. In addition, batch-to-batch reproducibility was excellent. The results demonstrate the excellent scale-up ability and potential application of this new photobleaching agar extraction process on a commercial scale. The agar yield and gel strength for 5% NaOH modified agar were 26.8% and 1,897 g cm(-2), while those for 3% NaOH modified agar were 28.2% and 1,287 g cm(-2), respectively. It is clear that the agar yield and quality can be manipulated via alkali modification in this new eco-friendly extraction to meet market demands

Pervaporation Process with PDMS/PVDF Hollow Fiber Composite Membrane to Recycle Phenol from Coal Chemical Wastewater

To treat coal gasification wastewater containing phenol, polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) hollow fiber composite membrane was made by dynamic negative pressure coating method, using PVDF hollow fiber membrane as base membrane, PDMS as modifying membrane material, to improve pervaporation performance of PDMS by the cross-linking modification. The influence of cross-linking agent, PDMS concentration, coating time on pervaporation performance of the composite membrane was investigated. Actual coal chemical wastewater with phenol concentration 1600-1800 mg/L, COD 13000-15000 mg/L was treated by the obtained PDMS/PVDF composite membrane, and at temperature 70℃, the flow rate of 10 L/h, pressure under membrane 3KPa, phenol flux 16.81 g/(m2·h), separation factor reaches 8.103