Straw is an important fiber material for virgin pulp production in some Asian countries.However,the cooking black liquor from straw is relatively difficult to recover using conventional Tomlinson process due to the presence of silica.Gasification with direct causticization has been thought a promising way to recover wood kraft black liquor thus drawn a lot of attentions in some North America and Nordic countries.Whether the concept is suitable for straw black liquor is not clear yet due to the possible interaction between silica and direct causticization agents.This paper took TiO2 and recycled Na2O?3TiO2 as direct causticization agents,and found that it is different in silica transfer mechanism between these two agents.As to TiO2,most of silica retained in the solid residue after hydrolysis,while nearly all of the silica transferred to hydrolyzing derived white liquor when using Na2O?3TiO2.This characteristic means that straw black liquor direct causticization process may need further lime causticization to improve the sodium recovery efficiency.Enlightened by chlor-alkali industry,the straw black liquor was treated by electrolysis method to recover NaOH and hydrogen at cathode,and leaving low sodium black liquor and precipitated silica at anode.The low sodium and silica content straw black liquor from electrolysis experiment was conducted direct causticization recycling using Na2O?3TiO2 again,and obtained a sodium recovery efficiency of no less than 85%.The results show a technical feasibility of straw black liquor direct causticization process if silica could be removed effectively.