Veera Gnaneswar Gude

Optimization of direct conversion of wet algae to biodiesel under supercritical methanol conditions.

This study demonstrated a one-step process for direct liquefaction and conversion of wet algal biomass containing about 90% of water to biodiesel under supercritical methanol conditions. This one-step process enables simultaneous extraction and transesterification of wet algal biomass. The process conditions are milder than those required for pyrolysis and prevent the formation of by-products. In the proposed process, fatty acid methyl esters (FAMEs) can be produced from polar phospholipids, free fatty acids, and triglycerides. A response surface methodology (RSM) was used to analyze the influence of the three process variables, namely, the wet algae to methanol (wt./vol.) ratio, the reaction temperature, and the reaction time, on the FAMEs conversion. Algal biodiesel samples were analyzed by ATR-FTIR and GC-MS. Based on the experimental analysis and RSM study, optimal conditions for this process are reported as: wet algae to methanol (wt./vol.) ratio of around 1:9, reaction temperature and time of about 255 °C, and 25 min respectively. This single-step process can potentially be an energy efficient and economical route for algal biodiesel production.

Optimization of microwave-assisted transesterification of dry algal biomass using response surface methodology

The effect of microwave irradiation on the simultaneous extraction and transesterification (in situ transesterification) of dry algal biomass to biodiesel was investigated. A high degree of oil/lipid extraction from dry algal biomass and an efficient conversion of the oils/lipids to biodiesel were demonstrated in a set of well-designed experimental runs. A response surface methodology (RSM) was used to analyze the influence of the process variables (dry algae to methanol (wt/vol) ratio, catalyst concentration, and reaction time) on the fatty acid methyl ester conversion. Based on the experimental results and RSM analysis, the optimal conditions for this process were determined as: dry algae to methanol (wt/vol) ratio of around 1:12, catalyst concentration about 2 wt.%, and reaction time of 4 min. The algal biodiesel samples were analyzed with GC-MS and thin layer chromatography (TLC) methods. Transmission electron microscopy (TEM) images of the algal biomass samples before and after the extraction/transesterification reaction are also presented.

Potable water recovery from As, U, and F contaminated ground waters by direct contact membrane distillation process.

In this study, the feasibility of the direct contact membrane distillation (DCMD) process to recover arsenic, uranium and fluoride contaminated saline ground waters was investigated. Two types of membranes (polypropylene, PP; and polytetrafluoroethylene, PTFE) were tested to compare the permeate production rates and contaminant removal efficiencies. Several experiments were conducted to study the effect of salts, arsenic, fluoride and uranium concentrations (synthetic brackish water with salts: 1000-10,000 ppm; arsenic and uranium: 10-400 ppb; fluoride: 1-30 ppm) on the desalination efficiency. The effect of process variables such as feed flow rate, feed temperature and pore size was studied. The experimental results proved that the DCMD process is able to achieve over 99% rejection of the salts, arsenic, fluoride and uranium contaminants and produced a high quality permeate suitable for many beneficial uses. The ability to utilize the low grade heat sources makes the DCMD process a viable option to recover potable water from a variety of impaired ground waters.

Membrane Distillation for Desalination and Other Separations

Membrane distillation is an emerging membrane technology used for desalination of seawater or brackish water, solution concentration, recovery of volatile compounds from aqueous solutions and other separation and purification processes. Membrane distillation differs from other membrane technologies in that the driving force for separation is the difference in vapor pressure of volatile compound across the membrane, rather than total pressure. The main advantage of membrane distillation over the conventional thermal distillation is that membrane distillation could occur at a much lower temperature than the conventional thermal distillation. The membranes used in membrane distillation are hydrophobic, which allow water vapor to pass through but not liquid solution. The vapor pressure gradient is created by heating the feed solution and cooling/purging the condensate in the permeate side. Therefore, membrane distillation enables separation to occur below the normal boiling point of the feed solution and could utilize low-grade heat from alternative energy sources. The objective of this review is to cover the basic principles and configurations of membrane distillation process, membrane physical characteristics, heat and mass transfer characteristics, and the effect of operating conditions. Also, major applications of this new technology in desalination, food industry and environmental protection, and latest patent developments and future trend in membrane distillation are presented.