Abstract: In order to optimize the preparation conditions of lignin quaternary ammonium salt embedding urea and explore its application in the slow-release fertilizer production, lignin quaternary ammonium salt-urea (GCL-QA-U) crosslinked by glutaraldehyde was synthesized through inverse suspension method using trimethyl lignin quaternary ammonium salt (L-QA) as raw material, the Span 80 as dispersing agent, and glutaraldehyde as the crosslink agent. Its structure was characterized by FT-IR. The effects of the conditions, i.e., the dosage of crosslink agent, rotate speed, reaction time,and the dosage of dispersing agent, on the embedding of urea were discussed so as to obtain the best process conditions and product. Slow-release performance was then measured by water soluble and soil column leaching method. The results showed that quaternary amine group were successfully grafted. Urea was embedded in the L-QA, in which nitrogen content was 1.98 % and nitrogen content of GCL-QA-U was 2.88 %. The best process conditions of GCL-QA-U was the dosage of glutaraldehyde 4 mL, reaction time 2 h, rotate speed 200 r/min, and the dosage of dispersing agent 1.0 mL. And the maximal embedding rate of urea in GCL-QA-U was 41.61 %. The water soluble and soil column leaching method concluded that the urea accumulatived release amount were 5 % and 3.86 % during 24 h, respectively. The urea accumulatived release amount were 79.47 % and 74.80 % during 28 day, respectively. The slow-release effect of GCL-QA-U met the standard of slow-release fertilizer (GB-T23348—2009).

Key words: trimethyl lignin quaternary ammonium salt, urea, embedding, glutaraldehyde, slow-release