Dissertation/Thesis Abstract

Synthesis of Bi-Functional Activated Carbon for Removal of p-Cresol and Ammonia
by Zhu, Yiying, Ph.D., North Carolina State University, 2016, 232; 10585505
Abstract (Summary)

p-Cresol and ammonia are two major pollutions generally present in industrial, agricultural, and domestic wastewaters, which pose a significant threat to the environment as well as public health. Especially, North Carolina ranks second in swine production in the US and the enormous amount of feces, urine, and unconsumed feed are prone to microbiologically decompose into p-cresol and ammoniacal nitrogen. It is of great importance to minimize these pollutants in the wastewater prior to their release to the environment. The adsorption using activated carbon is highly efficient and easy to adopt compared to other treatment techniques.

Hence, the present research was focused on the use of the agricultural residues to convert into efficient low-cost activated carbons for p-cresol and ammonia uptake. The objectives were to (1) synthesize a highly active alkaline activated carbon for removal of pcresol in aqueous single-solute systems, (2) synthesize an effective acidic activated carbon for adsorption of ammonia in aqueous single-solute systems, and (3) explore a bi-functional activated carbon capable of adsorbing p-cresol and ammonia simultaneously in aqueous double-solute systems.

For the first objective, a coconut shell-based activated carbon (CSAC) was first synthesized via physiochemical activation of zinc chloride. Batch experiments were conducted for p-cresol adsorption to evaluate the performance of the activated carbon. The effects of different operation parameters such as initial adsorbate concentration (25-500 mg L-1), agitation speed (0-200 rpm), solution pH (2-12), and adsorbent dosage (0.50-3 g 100 mL-1) were examined. Kinetic and equilibrium studies were also carried out. The maximum monolayer p-cresol adsorption capacity for CSAC was found to be 30.23 mg g-1 at 293 K, 31.57 mg g-1 at 303 K, and 32.77 mg g-1 at 313 K. To improve the adsorption capacity for p-cresol further, a coconut shell-based activated carbon (CSAC-SH) was prepared using sodium hydroxide. The characterization of CSAC-SH via Brunauer-Emmitt-Teller (BET) surface area analyzer, scanning electron microscope (SEM), and Boehm titration indicated that CSAC-SH has a well-developed microporous/mesoporous structure with a relatively high surface area of 520.16 m2 g-1 and rich in basic surface functional groups. A maximum monolayer p-cresol adsorption capacity of 256.9 mg g-1 (298 K) indicated that CSAC-SH was effective in p-cresol uptake.

For the second objective, an avocado seed based-activated carbon (AAC-MA) was synthesized using methanesulfonic acid. The effects of pH (3-9), adsorbent dosage (1-20 g L- 1), initial ammonia concentrations (50-450 mg L-1) and contact time (0-6 h) on ammonia mitigation were investigated. The pseudo-second order kinetic model and Langmuir isotherm model were found to give the best data correlation to the kinetic and equilibrium data, respectively. A maximum monolayer adsorption capacity of 5.446 mg g-1 was found of ammonia on AAC-MA at 298 K.

For the third objective, the previously obtained activated carbon AAC-MA was further investigated by adsorption of p-cresol from aqueous single-solute systems. AAC-MA showed reasonably well adsorption capacity for p-cresol of 88.03 mg g-1. Further, the same adsorbent was used for simultaneous adsorption of p-cresol and ammonia in the binary mixture system. Equilibrium studies were conducted to determine the adsorption behavior and extended Langmuir isotherm model was found to best suitable to describe the experimental data of both p-cresol and ammonia. Negligible competitive adsorption between p-cresol and ammonia was deduced and 87.79 and 3.393 mg g-1 maximum monolayer adsorption capacities were determined for p-cresol and ammonia in the double solute systems, respectively.

The results indicate that removal of ammonia and p-cresol may be effectively accomplished via activated carbons prepared from agricultural residues. If applied to animal agricultural waste management treatment systems, the odor and other pollutants can be minimized, thereby making animal agricultural sustainable and environment friendly.

Indexing (document details)
Advisor: Kolar, Praveen
School: North Carolina State University
School Location: United States -- North Carolina
Source: DAI-B 78/08(E), Dissertation Abstracts International
Subjects: Agricultural engineering, Chemical engineering, Environmental engineering
Keywords: Activated carbon, Ammonia removal, Cresol, Physiochemical activation, Swine production
Publication Number: 10585505
ISBN: 978-1-369-64183-7
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