A zero-waste one step method to produce carboxy nanocellulose from the untreated barley and wheat straws

Abstract

A zero-waste simple method was developed to produce carboxy nanocellulose directly from the untreated barley and wheat straw by treating with nitric acid (55%) and sodium nitrite at 40 °C for 12 h. This method significantly reduced the need for toxic chemicals such as TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)-oxyl) and radical generating chemicals. The process also reduced the usage of corrosive bases and acids and energy demand during the pretreatment process for the multi-step acid hydrolysis of biomass. Moreover, the by-product can be easily neutralized with the addition of NaOH, and the neutralized solution can be concentrated to obtain sodium nitrate which can be utilized as a fertilizer. The current method produces rod shaped and spherical particles of carboxy nanocellulose from the barley and wheat straw respectively with lower crystallinity (ca. ⁓30% of crystallinity index) than the barley and wheat straw itself (ca. ⁓60% of crystallinity index) as evidenced from the grazing incidence X-ray diffraction (GIXRD) technique. The conductometric titration revealed a high concentration (ca. ⁓2.6 mmol/g) of surface carboxylic (-COOH) acid groups and this result is supported by the high zeta potential value (ca ⁓-40mV) for the synthesized carboxy nanocellulose.

Keywords:

• Carboxy nanocellulose
• barley straw
• wheat straw
• nitric acid oxidation

Acknowledgments

Dr. Sanmitra Barman sincerely acknowledges Center for Advanced Materials and Devices (CAMD) at BML Munjal University for providing infrastructure for carrying out experiments. Dr. Barman sincerely thanks Mr. Ashish Dhillon from the department of chemistry, IIT Delhi for help in carrying out few characterizations at the central instrumentation facility at IIT Delhi. Lastly, Dr. Barman sincerely thanks Dr. Soumik Siddhanta from the department of chemistry IIT Delhi, for providing valuable suggestions during the writing of the manuscript.

Authors’ contributions

Sanmitra Barman conceptualized, performed the experiments, analyzed the data for all the characterizations and wrote the manuscript. Sambhunath Bera performed the GIXRD and analyzed the GIXRD data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data are avaialable at 10.6084/m9.figshare.24449122