Response surface modeling and optimization of direct contact membrane distillation for water desalination

• Regression models were established by response surface methodology in DCMD process.
• The models were proved to be able to predict the responses accurately.
• Interaction effects of operational and module-configural factors were investigated.
• Optimal conditions for multi-objectives were determined and confirmed.

Response surface methodology was applied for modeling and optimization of direct contact membrane distillation (DCMD) for water desalination with PVDF hollow fiber membrane. The optimization objectives included average permeate flux, water productivity per unit volume of module, water production per unit energy consumption, and a comprehensive index to find out a balance among high water flux, high production, and low energy consumption. Effects of both operating parameters and configuration parameters of membrane module, including inlet temperatures of feed and permeate, flow velocity of feed solution, module packing density, and length-diameter ratio of module, on the objectives were investigated. The models for predicting the objectives were developed and statistically validated by analysis of variance. The binary interaction effects of the variables on the objectives were illustrated and discussed. All of the objectives were significantly influenced by the interaction effects of the variables. Under the optimum conditions, 67.1 kg/(m2·h) average permeate flux, 4.9825 × 104 kg/(m3·h) water productivity per unit volume of module, 2.1839 × 10− 4 kg/kJ water production per unit energy consumption, and comprehensive index of 0.7587 were obtained within investigated experimental range. The experimental and predicted results are in good agreement confirming the validity of the models.

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