The present study focuses on the adsorption of organic matter mainly COD from pretreated landfill leachate of Lamdeng Khunou Solid Waste Management Plant, Manipur, India through the employment of H3PO4 treated activated carbon derived from Parkia speciosa (Petai) pods (PPAC). The adsorbent was analyzed for morphological and surface characterization by various methods including, Field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray Analysis (EDAX), Brunauer–Emmett–Teller (BET) surface area and pH at zero point charges ( pHZPC). The impacts of adsorption processes such as initial pH, temperature, equilibrium time and dose of adsorbent were considered to evaluate the performance of PPAC. At 20 °C, PPAC showed maximum COD removal of 93% within 90 min contact time, at optimum pH 2. Adsorption kinetic was able to explain by Lagergren’s pseudo-second-order equation and intraparticular diffusion models suggesting the combined behavior of both the physical and chemical adsorption of COD on PPAC. Through thermodynamics and isotherm studies, the adsorption of COD on PPAC is revealed to be exothermic with maximum monolayer coverage of 200 mg COD/g PPAC. The performance of the PPAC adsorbent is also compared with other existing reported adsorbents for treating leachate.

The adsorption process using GAC is one of the most secured methods to remove of phosphate from solution. This study was conducted by impregnating Cu(II) to GAC(GAC-Cu) to enhance phosphate adsorption for GAC. In the preparation of GAC-Cu, increasing the concentration of Cu(II) increased the phosphate uptake, confirming the effect of Cu(II) on phosphate uptake. A pH experiment was conducted at pH 4-8 to investigate the effect of the solution pH. Decrease of phosphate removal efficiency was found with increase of pH for both adsorbents, but the reduction rate of GAC-Cu slowed, indicating electrostatic interaction and coordinating bonding were simultaneously involved in phosphate removal. The adsorption was analyzed by Langmuir and Freundlich isotherm to determine the maximum phosphate uptake(qm) and adsorption mechanism. According to correlation of determination(R2), Freundlich isotherm model showed a better fit than Langmuir isotherm model. Based on the negative values of qm, Langmuir adsorption constant(b), and the value of 1/n, phosphate adsorption was shown to be unfavorable and favorable for GAC and GAC-Cu, respectively. The attempt of the linearization of each isotherm obtained very poor R2. Batch kinetic tests verified that ~30% and ~90 phosphate adsorptions were completed within 1 h and 24 h, respectively. Pseudo second order(PSO) model showed more suitable than pseudo first order(PFO) because of higher R2. Regardless of type of kinetic model, GAC-Cu obtained higher constant of reaction(K) than GAC.

The impregnated activated carbons were prepared by the incipient wetness method with the contents of KIO3 varied from 1.0~10 wt% as the impregnation material. The specific surface area and micropore volume of the rice hulls activated carbon were 2,600~2,800 m2/g and 1.1~1.4 cc/g, respectively. With increasing the contents of impregnation materials, the surface area and micropore volume decreased by 3~21%. However, The amounts of hydrogen sulfide adsorbed increased by 2.1~2.8 times depending on the impregnation content. The optimum contents of KIO3 were 2.4 wt%. Although the breakthrough time and adsorption capacity of hydrogen sulfide decreased with increasing temperature in the case of the unimpregnated activated carbons, they increased by 1.2~ 3.2 times for the case of the impregnated activated carbons. The optimum aspect ratio(L/D) was 1.0 and the adsorption amount of hydrogen sulfide enhanced with increasing the gas flow rate. The regeneration temperature was determined as 400℃ from the TGA experiment. The adsorption capacity of hydrogen sulfide with the impregnated activated carbon decreased gradually as the regeneration continued. The hydrogen sulfide adsorption amount of the regenerated activated carbon up to 4 times was still higher than that of the unimpregnated activated carbon.

In this paper, impregnated activated carbon fiber (IACF) was manufactured to pitch-based activated carbon fibers (ACF) with potassium hydroxide (KOH) by using wet impregnation method to raise nitrogen oxides (NOx) adsorptivity. The properties of IACF were observed using EPMA, TGA and DSC and NOx adsorptivity was observed at high and low temperature. Before and after adsorption was analyzed using ToF-SIMS for examine surface characterization of adsorbed NOx. The results showed that the better adsorptivity appeared for increasing KOH ratio. So, NOx adsorptivity showed result that is proportional between KOH and the adsorbed amount. On the other hand, adsorbent that manufactured without washing was better NOx adsorptivity than adsorbent that manufactured with washing. The behavior of adsorption show that crossing time of NO and NO2 delayed for a rising adsorptivity. And NO ratio increased but NO2 ratio decreased according as KOH ratio increases. NOx was confirmed through surface analysis that remain in NO2- and NO3- form on IACF surface.

Activated carbons with high surface area of 2,600 m2/g and high pore volume of 1.2 cc/g could be prepared by KOH activation of rice hulls at a KOH:char ratio of 4:1 and 850℃. In order to increase the adsorption capacity of hydrogen sulfide, which is one of the major malodorous component in the waste water treatment process, various contents of Na2CO3 and KIO3 were impregnated to the rice-hull activated carbon. The impregnated activated carbon with 5 wt.% of Na2CO3 showed improved H2S adsorption capacity of 75 mg/g which is twice of that for the activated carbon without impregnation and the impregnated activated carbon with 2.4 wt.% of KIO3 showed even higher H2S adsorption capacity of 97 mg/g. The improvement of H2S adsorption capacity by the introduction of those chemicals could be due to the H2S oxidation and chemical reaction with impregnated materials in addition to the physical adsorption of activated carbon.

Adsorption and desorption characteristics of methyl iodide at high temperature conditions up to 250℃ by TEDA-impregnated activated carbon, which is used for radioiodine retention in nuclear facility, was experimentally evaluated. In the range of temperature from 30℃ to 250℃, the adsorption capacity of base activated carbon decreased sharply with increasing temperature but that of TEDA-impregnated activated carbon showed higher value even at high temperature ranges. Especially, the desorption amount of methyl iodide on TEDA-impregnated carbon represented lower value than that on unimpregnated carbon. The breakthrough curves of methyl iodide in the fixed bed packed with base carbon and TEDA-impregnated activated carbon at high temperature were compared. TEDA-impregnated activated carbon would be applicable to adsorption process up to 150℃ for the removal of radioiodine in a nuclear facility.

Functionalized adsorbent has been synthesized by piperazine(Pz) on activated carbon. Quantitative estimations of CO2 were undertaken using gas chromatography with GC/TCD and the prepared adsorbents were characterized by BET surface area and FT-IR. It was also studied effect of various parameters such as piperazine loadings and adsorption temperature. The specific surface area decreased from 1212.0 m2/g to 969.8 m2/g by impregnation and FT-IR revealed a N-H functional group at about 1400 cm-1 to 1700 cm-1. The CO2 adsorption capacity at 20℃ and 50∼100℃ was as follow: AC > Pz(10)-AC> Pz(30)-AC> Pz(50)-AC at 20℃ and Pz(10)-AC > AC > Pz(30)-AC> Pz(50)-AC at 50∼100℃. Therefore, for high temperature flue gas condition, the Pz(10)-AC showed the highest adsorption capacity due to physical adsorption and chemical adsorption by amino-group content. The results suggest that activated carbon impregnated with Pz is an effective adsorbent for CO2 capture from real flue gases above 50℃.