Effect of pyrolysis conditions on chemical properties of carbonized rice husks for efficient NH4+ adsorption

Abstract

Ammonium ions (NH4+) are commonly found in contaminated water and are a contributing factor to water eutrophication. Carbonized rice husk, derived from various biomass sources, possesses a porous structure, and its characteristics are influenced by the feedstock and pyrolysis conditions. Hence, this study aimed to investigate the applicability of carbonized rice husk as an absorbent for NH4+ removal. The adsorption kinetics were analyzed using the Pseudo-first-order and Pseudo-second-order models, while the adsorption characteristics were assessed using the Langmuir and Freundlich isotherms. The adsorption rate of NH4+ by carbonized rice husk increased until 240 min and then gradually approached equilibrium state. Notably, the highest NH4+ adsorption rate was observed in pH 7.1 carbonized rice husk 36.045 mg/g∙min. Moreover, the NH4+ adsorption capacity exhibited an increase with increasing concentration and quantity of the solution. The pH of the carbonized rice husk was found to influence the NH4+ adsorption process, with higher pH values corresponding to increased NH4+ adsorption rates. The NH4+ sorption rate carbonized rice husk was higher in pH 11.0 at 31.440 mg/g compared to pH 6.1 (7.642 mg/g) and pH 7.1 (10.761 mg/g). These findings highlight the impact of pyrolysis conditions on the adsorption characteristics of carbonized rice husk.

Neutral rice husk biochar amendment effectively mitigates ammonia emissions and improves Chinese Cabbage yield in different nitrogen rates condition

“…Biochar, a carbonrich material, is obtained through the pyrolysis of agricultural residues, biomass, and organic waste ingredients under relatively high temperatures and oxygen-limited conditions 7,9,10,11,12 . It has garnered attention for its distinctive characteristics, such as carbon (C) sequestration 7,13 , promotion of plant growth 14,15 , enhancement of soil pH 4 , optimization of soil health 12 , provision of a habitat for microorganisms 13 , and the adsorption of heavy metals and nutrient contents 4,16 .…”

“…Furthermore, biochar has the ability to absorb organic N, ammonium ions (NH 4 + ), and gaseous NH 3 through its functional groups and microspores, resulting in reduced N losses 15 . These properties of biochar are evident in the reduced N loss observed in agricultural soils treated with N fertilizers in the presence of biochar 18 .…”