A general synthetic method to make Fe3O4-δ (activated magnetite) is the reduction of Fe3O4 by H2 atmosphere. However, this process has an explosion risk. Therefore, we studied the process of synthesis of Fe3O4-δ depending on heat-treatment conditions using FeC2O4·2H2O in Ar atmosphere. The thermal decomposition characteristics of FeC2O4·2H2O and the δ-value of Fe3O4-δ were analyzed with TG/DTA in Ar atmosphere. β-FeC2O4·2H2O was synthesized by precipitation method using FeSO4·7H2O and (NH4)2C2O4·H2O. The concentration of the solution was 0.1 M and the equivalent ratio was 1.0. β-FeC2O4·2H2O was decomposed to H2O and FeC2O4 from 150˚C to 200˚C. FeC2O4 was decomposed to CO, CO2, and Fe3O4 from 200˚C to 250˚C. Single phase Fe3O4 was formed by the decomposition of β-FeC2O4·2H2O in Ar atmosphere. However, Fe3C, Fe and Fe4N were formed as minor phases when β-FeC2O4·2H2O was decomposed in N2 atmosphere. Then, Fe3O4 was reduced to Fe3O4-δ by decomposion of CO. The reduction of Fe3O4 to Fe3O4-δ progressed from 320˚C to 400˚C; the reaction was exothermic. The degree of exothermal reaction was varied with heat treatment temperature, heating rate, Ar flow rate, and holding time. The δ-value of Fe3O4-δ was greatly influenced by the heat treatment temperature and the heating rate. However, Ar flow rate and holding time had a minor effect on δ-value.

Activated magnetite (Fe3O4-δ) was applied to reducing CO2 gas emissions to avoid greenhouse effects. Wet and dry methods were developed as a CO2 removal process. One of the typical dry methods is CO2 decomposition using activated magnetite (Fe3O4-δ). Generally, Fe3O4-δ is manufactured by reduction of Fe3O4 by H2 gas. This process has an explosion risk. Therefore, a non-explosive process to make Fe3O4-δ was studied using FeC2O4·2H2O and N2. FeSO4·7H2O and (NH4)2C2O4·H2O were used as starting materials. So, α-FeC2O4·2H2O was synthesized by precipitation method. During the calcination process, FeC2O4·2H2O was decomposed to Fe3O4, CO, and CO2. The specific surface area of the activated magnetite varied with the calcination temperature from 15.43 m2/g to 9.32 m2/g. The densities of FeC2O4·2H2O and Fe3O4 were 2.28 g/cm3 and 5.2 g/cm3, respectively. Also, the Fe3O4 was reduced to Fe3O4-δ by CO. From the TGA results in air of the specimen that was calcined at 450˚C for three hours in N2 atmosphere, the δ-value of Fe3O4-δ was estimated. The δ-value of Fe3O4-δ was 0.3170 when the sample was heat treated at 400˚C for 3 hours and 0.6583 when the sample was heat treated at 450˚C for 3 hours. Fe3O4-δ was oxidized to Fe3O4 when Fe3O4-δ was reacted with CO2 because CO2 is decomposed to C and O2.

Transformed cassava plants were successfully produced from friable embryogenic calli derived from leaf lobes byAgrobacterium tumefaciens-mediated transformation. We used A. twnefaciens strain LBA4404 containing pCAMmPHY whichcontained a binary vector with