Synthesis of Activated Carbon from Citric Acid Residue by Phosphoric Acid Activation for the Removal of Chemical Oxygen Demand from Sugar-Containing Wastewater

Abstract

Over 2 million tons of citric acid residue (CAR) are generated from citric acid production in China each year. Thus, it is of great significance to find a suitable method for recycling the waste products of citric acid fermentation. Herein, activated carbon (AC) samples were prepared from CAR with phosphoric acid activation. Effects of impregnation ratio, activation time, and activation temperature on pore structure and surface functional group formation were evaluated. AC prepared by 1.5 h of pyrolysis in nitrogen at 550°C from CAR and phosphoric acid at an impregnation ratio of 2.0 (CAR-AC-2.0) had the largest specific surface area (786 m 2 /g) and total pore volume (0.71 mL/g). The surface morphologies and chemical properties of AC samples were characterized by scanning electron microscopy, thermogravimetric analysis, elemental analysis, and Fourier transform infrared spectroscopy (FTIR), and their adsorption capacities for methylene blue (MB) and iodine were tested. There were rare functional groups on the surfaces of CAR-AC-2.0, and the adsorption amounts of CAR-AC-2.0 for iodine and MB reached up to 729 and 121 mg/g, respectively. CAR-AC-2.0 was an ideal adsorbent for removing organic matters from solutions and wastewater. Adsorption efficiency of CAR-AC-2.0 for chemical oxygen demand (COD) from sugar-containing wastewater was 291.6 mg/g, and the removal efficiency was 80.9% when the dosage was 15 g/L. This study provided a new strategy for removing COD from fermentation wastewater with high efficiency and low cost.

Effects of Phosphate and Thermal Treatments on the Characteristics of Activated Carbon Manufactured from Durian (Durio zibethinus) Peel

“…The significant difference between the morphology of AC (Figure 3) and C (Figure 2) is the formation of porosity as a result of the activation of phosphoric acid on carbon to produce new products in the form of phosphate esters and polyphosphates [24]. The morphology of the durian peel carbonized at 300 °C showed a wrinkled carbon surface without the pores because the durian peel carbon has not been able to decompose the volatile content [48,49].…”

“…It is due to the intensive interaction between the phosphoric acid molecules and the carbon structure. So, the carbon decomposes into cellulose to form phosphates oxide (P 2 O 5 ), which forms pores [24]. The pore size decreased sharply as the activator concentration increased from 10% to 20%.…”

Kinetic studies on the adsorption of uranium on a mesoporous impregnated activated carbon

“…The micropore diameter of the PAC was 1.81 nm while the mesopore diameter (r -, nm) was calculated according to the following Equation ( 4 The pore size distribution of PAC showed the micro/mesoporosity (Figure 2b). Actually, the behavior of pistachio nutshell with phosphoric acid creates a high surface area and allows the development of both micropores and mesopores in the activated carbon [19].…”

“…The linearized form of the D-R model is assumed as Equation ( 18), ln q e = ln q m − βε 2 (18) where β is the activity coefficient related to mean adsorption energy (mol 2 /J 2 ) and ɛ is the Polanyi potential. Where, The Polanyi potential [54] can be designed using the Equation (19),…”

Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater

“…During the process of biomass gasification, liquefaction and combustion, biomass pyrolysis technology is indispensable for converting biomass to liquid fuel or other valuable chemical products [8][9][10] . Recently, many studies have focused on the potential of biofuel production from microalgae cultivated in wastewater [11][12][13][14] .…”