Diazonuim silica was prepared and used to remove nitrites in wetland waters. Raw silica was chlorinated using phosphorous pentachloride (PCl5). Chlorinated silica was further reacted with ethylenediamine (EDA) under reflux to give aminated silica. Thereafter, aminated silica was protonated to yield diazonium silica which was used as the adsorbent. The prepared diazonium silica material was characterized using Fourier Transform Infrared (FT-IR) showing bands at wavenumbers 1049 and 791 cm-1 of the anti-symmetric and symmetric stretching modes (Si-O-Si) of SiO4. The shift in spectra band of Si-O-Si from 1051cm-1 in raw silica to 1049cm-1, was attributed to diazonium silica. Additionally, a new open chain azo (N=N) group band was found in the region 1575cm-1 -1630cm-1. The physical adsorption parameters examined using batch adsorption system including: pH, initial concentration, contact time and temperature were made using sorption models, adsorption kinetics and thermodynamics. The results obtained showed 3.0 as the optimal pH for adsorption of NO2 -, 303K as the optimal temperature, optimum contact time as 60 minutes and optimal initial concentration as 20ppm. The adsorption capacity of nitrites using diazonium silica adsorbent was achieved at 16.45mg/g. For sorption of nitrites in diazonuim silica, Langmuir isotherm model was obeyed according to correlation coefficient R2 = 0.97182 close to unity. Adsorption kinetics of nitrites in diazonium silica pseudo second order was best obeyed while, thermodynamic parameters revealed that the sorption of nitrites into diazonium silica was exothermic in nature. From the results obtained, diazonium silica is an efficient adsorbent for adsorption of nitrites compared to raw silica.