H2O2 modified-hydrochar derived from paper waste sludge for enriched surface functional groups and promoted adsorption to ammonium

Abstract

Abstract Background This work investigated adsorption behaviors of NH4+ onto H2O2 modified paper waste sludge-derived hydrochar (HPSH). Methods Effect of various operational parameters, including modification ratio, solution pH, adsorbent dosage, initial NH4+ concentration and contact time on NH4+ adsorption was studied. Besides, the NH4+ adsorption isotherms, kinetics and thermodynamics at different operational temperatures were systematically investigated. The textural, morphology, crystalline structure and surface chemistry characteristics of hydrochars were analyzed. Specially, NH4+ adsorption mechanisms controlled by enriched oxygen-containing surface functional groups by treatment of H2O2 onto hydrochars were deeply discussed. Significant findings The results showed that the optimal treatment ratio between H2O2 and PPSH was 40. Characterization data indicated H2O2 modification increased the oxygen-containing functional groups on the hydrochar surface. The maximum adsorption capacity of HPSH-40 was 7.941\xa0mg/g which was higher that of PPSH about double. NH4+ adsorption onto hydrochars was well described by the pseudo-second-order model and Langmuir isotherm. The thermodynamic studies showed NH4+ adsorption onto hydrochars was endothermic in nature. The mechanisms of NH4+ adsorption onto hydrochars included π-cation interaction, cation exchange, surface complexation and electrostatic attraction which were attributed to the vital role of enriched oxygen-containing surface functional groups on hydrochar s surface.