A STATISTICAL ANALYSIS OF A PACKED TOWER DEHUMIDIFIER

ABSTRACT

A dehumidifier is the heart of a liquid desiccant cooling system. In these systems, air is dehumidified using liquid desiccants and cooled with heat exchangers and/or evaporative coolers [I]. A Statistical Analysis Software (SAS) regression analysis was performed on experimental data from a packed tower desiccant dehumidifier tested at Texas Tech. The purpose of this analysis was to determine simple functional relationships for the liquid desiccant dehumidifier for use in computer models of liquid desiccant space cooling systems.

Six factors and four dependent variables were defined and four regression models were determined. These regression models were reduced to three factor models. The packed tower regression analysis showed Texas Tech's “Cost Effective Liquid Desiccant” (CELD) to be a well behaved stable desiccant solution.     

Biosorption properties of dried Neurospora crassa for the removal of Burazol Blue ED dye

Biosorption potential of dried Neurospora crassa for Burazol Blue ED was studied with respect to pH, equilibrium time, biomass concentration and temperature to determine equilibrium and kinetic model parameters. The most suitable pH, equilibrium time and biomass concentration were determined as 1 ± 0.2, 60 min and 1.6 g L^− 1, respectively, at 20 °C ± 1.0. The equilibrium data was best described by the Langmuir isotherm model. The maximum biosorption capacity (q_m) of biomass obtained from the Langmuir fit was 110.1 mg g^− 1 biomass at 30 °C. The overall biosorption process was best described by the pseudo-second-order kinetic model. The biosorption process was found to be favored at higher temperatures.     

Kinetics and thermodynamics of lead (II) adsorption on lateritic nickel ores of Indian origin

The lead adsorption from aqueous solution was studied in batch experiments using two typical Indian origin nickel lateritic ores having high (46.29%) and low iron content (28.56%) coded as NH and NL respectively. The adsorption was found to be strongly dependent on pH of the medium showing increase in uptake of Pb(II) from 11.0 to 53% and 8.2 to 44% for NH and NL samples respectively with the increase in pH in the range of 2.0–5.23. The time data generated at different temperatures for both the samples fitted well to second-order kinetic model and Elovich equation. The later is indicative of a chemisorption process. The +ve ΔH° values (8.90 and 10.29 kJ mol⁻¹ for NH and NL samples) support the endothermic nature of adsorption. The +ve ΔS° values (28.56 and 29.40 kJ mol⁻¹ K⁻¹ for NH and NL respectively) suggest that the adsorption occurs with internal structural changes. The activation energy was estimated to be 7.6 and 3.12 kJ mol⁻¹ for NH and NL respectively. The thermodynamic activation parameters were also evaluated using Eyring equation. The loading capacities of NH and NL were estimated to be 44.4 and 28.45 mg g⁻¹ respectively under the experimental conditions: adsorbent concentration 2 g l⁻¹, time 30 min, temperature 308 K and pH 5.23. Data fitted well to Langmuir and Freundlich isotherm models for NH while in case of NL only Langmuir isotherm showed good fit. Due to high loading capacities and favorable kinetics, these materials can be utilized for Pb(II) removal from aqueous solutions.     

Removal of 2,4-D, MCPA and Metalaxyl from water using Lewatit VP OC 1163 as sorbent

The objective of this study was to investigate the use of organic polymer resin Lewatit VP OC 1163 to remove the pesticides MCPA, 2,4-D, and Metalaxyl. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data obtained from three measurements (SAC₂₅₄, COD, and KMnO₄ Demand) of pesticide adsorption. The adsorption capacities of the pesticides studied followed the order: Metalaxyl > 2,4-D > MCPA. S-type isotherms were obtained, which indicates a moderate interaction between adsorbate molecules and adsorbent. A series of column tests were performed to determine the breakthrough curves using organic polymer resin Lewatit VP OC 1163. The good adsorbability of Metalaxyl on Lewatit VP OC 1163 could be confirmed by the column experiments. The ionic characters of MCPA and 2,4-D are responsible for the short breakthrough times in the Lewatit VP OC 1163 column. It has been concluded that lower the pK_a value, the greater is the adsorption for the uncharged (neutral) organic polymer resin. The key parameters that can be derived from this overview are thus, in order of relative influence: pK_a, solubility, and hydrophobicity.     

STUDIES ON THE ADSORPTION OF FURFURAL FROM AQUEOUS SOLUTION ONTO LOW-COST BAGASSE FLY ASH

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (pH₀), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be pH₀ ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10^-13 m²/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS⁰) and heat of adsorption (ΔH⁰) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG⁰) indicates the feasible and spontaneous adsorption of furfural on BFA.