Abrar Muslim

Simulation of Free Chlorine Decay and Adaptive Chlorine Dosing by Discrete Time-Space Model for Drinking Water Distribution System

An ideal drinking water distribution system (DWDS) must supply safe drinking water with free chlorine residual (FCR) in the form of HOCl and OCl- at a required concentration level. The FCR as a disinfectant decreases over time due to chemical reactions in the bulk phase and at the pipe wall in the DWDS. In order to supply drinking water with the FCR concentration within the safety range of 0.2-0.6 mg/l at the points of water consumption, it is important to develop a dynamic model of the FCR using a discrete time-space model (DTSM) that accounts for free chlorine transport in the axial direction by convection, diffusion and the decay kinetic. A DTSM has been developed using Finite Difference Method (FDM) to predict the FCR in single pipes in the DWDS. The DTSM has been computed using Matlab 7.0.1 and tested with step inputs and rectangular pulse inputs to estimate the FCR at any point in the pipes over time. Data found in the literature have been used to validate the DTSM. The modelling and simulation study shows that the water velocity significantly affects the FCR concentration distribution along the pipe. Due to the fluctuation of the drinking water demand, a model-based adaptive chlorine dosing scheme is proposed to control the proper injection of chlorine.

Adsorption of Copper Complexes on Anion Exchange Resin in Non- Ammoniacal and Ammoniacal Thiosulfate Leaching Systems

The leaching of copper using thiosulfate reagent as an alternative reagent to cyanide has been investigated since it is almost presented in gold thiosulfate leaching. This paper addressed the investigation of adsorption of copper complexes on anion exchange resin in non-ammoniacal and ammoniacal thiosulfate leaching systems.The work provided the experimental procedures for the adsorption of copper complexes on strong based anion exchange resin in non-ammoniacal and ammoniacal resin-solution systems. The result showed that increasing ammonia in the solution resulted in the diminishing total copper complexes on the resin. As the solution pH of resin-solution systems was maintained by the ammonia solution added in the system, the same effect of ammonia on the total copper complexes on resin was also shown. Overall, non-ammoniacal resin-solution system gave much better adsorption isotherm of copper complexes on resin, and the dominant species copper complexes on the strong based anion exchange resin was expected to be Cu(S2O3)35-based on leaching modelling.

Adsorption of Cu(II) Ions in Aqueous Solutions by HCl Activated Carbon of Oil Palm

Activated carbon was prepared from oil palm empty fruit bunch (OPEFB) by pyrolysis at 873.15 K in a furnace and chemical activation using 0.01 M HCl. Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and BET (Brunauer, Emmett and Teller) surface area analyses were taken into account to investigate the chemical functional group, to characterise the surface morphology and to determine total surface area the OPEFB AC, respectively. Experiments in batch mode were conducted to investigate Cu(II) adsorption capacity by the OPEFB AC whereas the system consisted of 1 g the OPEFB AC in 100 mL Cu(II) aqueous solution with initial concentration in the range of 10-70 mg/L, magnetic stirring at 75 rpm, room temperature of 300.15 K (± 2 K), at 1 atm and neutral pH over contact time in the range of 0-150 min. As the result, Cu(II) adsorption capacity increased exponentially over contact time and initial concentration. The Cu(II) adsorption kinetics followed the pseudo second order kinetics with the correlation coefficients (R 2), kinetics rate constant and equilibrium adsorption capacity being 0.98, 4.81 mg/g and 0.15/min, respectively for initial Cu(II) concentration being 58.71 mg/L. In addition, Cu(II) adsorption isotherm followed the Langmuir equation with the R2 value, the mono-layer and over-all adsorption capacity being 0.99, 5.92 mg/g and 0.17 L/mg, respectively.

Modelling and simulation of gold thiosulphate elution in ammoniacal thiosulphate resin solution system

Abstract The gold thiosulphate complex and gold thiosulphate–sulphite complex are formed in the adsorption and elution of gold thiosulphate in ammoniacal thiosulphate resin solution (ATRS) systems. This work proposed a mathematical model of gold thiosulphate elution based on mechanistic approach to predict the gold thiosulphate concentration along bed volumes. Adsorption experiment was conducted to highlight the charge distribution for thiosulphate, trithionate and gold thiosulphate adsorbed on resin at equilibrium. The proposed model was simulated to demonstrate the effect of parameter on the GTC and GTSC concentration in elution. Multivariable optimization approach was taken into account to obtain an optimal value of the GTC and GTSC elution parameters. As the results, the optimal anion exchange coefficients of GTC and GTSC elution were worked out becoming approximately 2.4E-04 and 1.5E-04 m2/s, respectively, with the optimal percentile of occupied sites for the GTC and GTSC being approximately 4.06 and 8.15%, respectively, for 0.2 M trithionate with the absence and presence of sulphite, respectively. Overall, the model-based results were in very good agreement with the results based on experimental data referenced with the correlation coefficient (R2 is approximately 0.9 and 0.94 for the GTC and GTSC, respectively).

Mechanistic Model-Based Speciation of Copper Complexes Adsorbed on Resin in an Ammoniacal Thiosulphate Resin-Solution System

Leaching and adsorption of copper complexes simultaneously occur in ammoniacal thiosulphate resin-solution systems. The reaction requires good control-independent variables to minimize reagent consumption as well as to obtain optimal adsorption of copper complexes on resin. This work proposed the development of a mechanistic model for the speciation of copper complexes in such a system. A set of experiments was conducted to validate the mechanistic model, and a comparison of the results showed that the mechanistic model is in very good agreement with the measurement-based result with the correlation coefficient (R2) being 0.997. In addition, the effect of independent variables was investigated. The effect of initial thiosulphate concentration on the most dominant copper complex species of Cu(S2O3)35− (S)(s) on resin and the possibility to minimize the reagent for the optimal concentration of species were investigated. In addition, a constraint was needed in the concentration of ammonia in solution to achieve the optimal adsorption of CuNH3(S2O3)23–(s) complex.

Modelling of Chlorine Contact Tank and the Combined Applications of Linear Model Predictive Control and Computational Fluid Dynamics

A dynamic model is developed to present chlorine decay in chlorine contact tank, and a single-input single-output (SISO) model that presents both chlorine dosing and decay process is developed in Simulink of Matlab software with considerations of the process disturbances of temperature and stagnant flow in the tank. A computational fluid dynamics (CFD) model of chlorine transport and decay in the tank is also developed with the use of mixture multiphase model to present the chlorine mixing and decay models in the tank. To optimally control free chlorine residual (FCR) concentration in the SISO system, a linear model predictive control (LMPC) is designed using the SISO system and LMPC control algorithm. The LMPC control objective is to regulate the optimal mass flow rates of gaseous chlorine to control the chlorine decay process inputs/outputs within the constraints. The results on the LMPC simulation using reference data from a real water plant show that the LMPC can control the FCR concentration in the tank within the constraint by regulating the optimal mass flow rates of gaseous chlorine. Commercial CFD software, FluentTM, has been used in this study to simulate the FCR distribution in the CCT channel based on the LMPC result.