Effect of CH3COOH and K2CO3 on Hydrothermal Pretreatment of Water Hyacinth (Eichhornia crassipes)

Excessive amounts of fast-growing water hyacinth have densely invaded many canals, lakes, and rivers throughout Thailand, damaging the ecology of local waterways. Water hyacinth is a typical lignocellulosic material and is recognized as a potential source of renewable energy. In this study, hydrothermal pretreatment accompanied by enzymatic hydrolysis of dried water hyacinth is investigated in the temperature range 160–220 °C, using a hydrothermal ball-mill reactor; this enables hydrothermal pretreatment and ball-mill pulverization to be conducted simultaneously. The effects of CH3COOH and K2CO3 on the liquid composition were investigated experimentally (C CH3COOH = 0.5–1.0 wt %, C K2CO3 = 0.5 wt %). In the absence of CH3COOH and K2CO3 at 220 °C, a glucose yield of 0.267 was obtained. The highest glucose yield of 0.855 was achieved at 200 °C with C CH3COOH = 0.75 wt % and water hyacinth intake = 10 wt %. In the presence of 0.5 wt % K2CO3, a glucose yield of 0.195 was obtained at 220 °C. The addition of K2CO3 did not suppress hydrolysis in the hydrothermal pretreatment. The autocatalytic effect of acid production in the hydrothermal pretreatment is therefore not large. A pseudofirst-order kinetic model with regard to cellulose content was developed to explain the conversion mechanism of cellulose to glucose in the hydrothermal pretreatment process.