Research Of Ammonia Nitrogen Electrode Based On Nanocomposite Material Modified For Water Quality

Ammonia-N is one of the main forms of nitrogen in aquaculture water and,is an indispensable source of protein synthesis in aquatic organisms.With the development of agricultural and industrial production in recent years,it is serious that release of ammonia nitrogen to environment is keeping increasing,it has greatly affected the ammonia-N concentration in aquaculture water.What is more,high ammonia-N concentration will makes toxic to aquatic organism,even kills them all,which threatens aquaculture production safety;what is the worse,high ammonia-N can makes water eutrophication,destroys the ecological balance,and harms the health of aquatic organisms.Therefore,the real time detection of ammonia-N is of great significance in preventing the deterioration of aquaculture water and aquatic organism disease,in ensuring the safety of aquatic products.In the process of ammonia-N detection in the water,due to the effect of physical and biological process,such as temperature,pH,atmosphere-ocean air exchange,sedimentation,biological absorption and release,it is difficult to achieve fast in-situ detection of ammonia-N and to achieve ideal accuracy.To solve the low accuracy,low anti-interference,complicated detection process,expensive maintenance,and off-line detection,a high-performance ammonia-N electrode using a combination of nanotechnology and electrochemical sensing is built,electrochemical behavior of NH3/NH4+ on nanometer electrode is studied.The sensing performance of ammonia-N electrode was verified,and applying sensor to detect ammonia-N in aquaculture water was validated.Specific work has been done as follows:(1)To handle with the high operation temperature,low sensitivity,and long response/recover time of detecting ammonia-N using only one kind metal nanomaterial or semiconductor metallic oxide,Fe2O3 is doped with Ag nanoparticles forming a new nanocomposite by chemical reduction method and hydrothermal synthesis method,which built a new type of NH3/NH4+ detection electrode.Further,the structure and elements of Ag/Fe2O3 are validated through qualitative and quantitative analysis.By the meantime,electrochemical response analysis of this modified electrode to NH3/NH4+ is experimented.The experimental results show that the electrode has a good linear response in the concentration range of 0-40?M(R2=0.961),the minimum detection limit is 0.89?M,the precision is 0.63%,and the electrode has good stability(2.33%)and repeatability(0.14%).So this new electrode based on Ag/Fe2O3 modified provided a new reliable detection method for the ammonia detection in water.(2)To deal with the low sensitivity and limited selectivity using pure CNTs to ammonia-N detection,Ag2O nanoparticle was modified into CNTs forming a new nanocomposite can improve the selectivity of ammonia-N,which built a novel electrode based on Ag2O/CNTs.The structure of Ag2O/CNTs is validated through characterization study,it also provides more reaction site,strengthens detection sensitivity to NH3/NH4+.Response performance of this modified electrode to NH3/NH4+ by C-V method is experimented.The experiment showed that this electrode had a good linear response to ammonia-N(R2=0.991)in the range of 0-130 ?g,the detection limit was 8.68 ?M,the linearity error was 10.54%,and RSD was 4.41%.So the electrode based on Ag2O/CNTs has good sensing performance and is suitable for the high-concentration detection of ammonia-N in aquaculture water.(3)Aiming at the problems of low sensitivity and precision in trace ammonia-N detection in water,Fe2O3/rGO nanocomposites was synthesize by wet chemical method,and a novel trace ammonia-N detection electrode was constructed based on Fe2O3/rGO nanocomposites.Through the characterization of Fe2O3/rGO nanocomposites,the structure and composition of the composites were verified.And,it is also proved that the high conductivity of rGO is the main factor to improve the sensitivity of ammonia-N detection.The electrochemical behavior of ammonia-N on Fe2O3/rGO modified electrode was studied by cyclic voltammetry method,the experimental results show that the electrode based on Fe2O3/rGO has good sensitivity and anti-interference performance for trace ammonia-N detection.The linearity was within the range of 0-1.0?M(R2=0.964).and the detection limit was 0.188 ?M,the linearity error was 34.07%,the precision RSD was 1.33%,Modified electrode based on Fe2O3/rGO-provides a new reliable method for the detection of trace ammonia-N in water.(4)A portable ammonia-N detector integrating electrochemical analysis and ammonia-N detection was designed and developed using above three kinds of nanocomposites modified electrodes,achieving electrochemical performance analysis,calibration,signal detection and acquisition.Based on the three-electrode measurement system,the hardware modular,program of low level computer,software of host computer are designed and development,achieving the performance analysis of the modified electrode using chemical analysis means,such as cyclic voltammetry.Electrode calibration and ammonia-N detection were performed using the constant potential method;data was acquired and processed by the host computer software.Finally,the actual measurement and validation were carried out in the fish pond and crab aquaculture water.The portable ammonia nitrogen detector can realize real-time in-situ measurement of ammonia-N in the aquaculture water.And the measurement accuracy and measurement range can well meet the actual application requirements in aquaculture.