Irvan Dahlan

Waste Material Adsorbents for Zinc Removal from Wastewater: A Comprehensive Review

This review examines a variety of adsorbents and discusses mechanisms, modification methods, recovery and regeneration, and commercial applications. A summary of available researches has been composed by a wide range of potentially low-cost modified adsorbents including activated carbon, natural source adsorbents (clay, bentonite, zeolite, etc.), biosorbents (black gram husk, sugar-beet pectin gels, citrus peels, banana and orange peels, carrot residues, cassava waste, algae, algal, marine green macroalgae, etc.), and byproduct adsorbents (sawdust, lignin, rice husk, rice husk ash, coal fly ash, etc.). From the literature survey, different adsorbents were compared in terms of Zn2

Selection of metal oxides in the preparation of rice husk ash (RHA)/CaO sorbent for simultaneous SO2 and NO removal.

In this work, the removal of SO(2) and NO from simulated flue gas from combustion process was investigated in a fixed-bed reactor using rice husk ash (RHA)/CaO-based sorbent. Various metal precursors were used in order to select the best metal impregnated over RHA/CaO sorbents. The results showed that RHA/CaO sorbents impregnated with CeO(2) had the highest sorption capacity among other impregnated metal oxides for the simultaneous removal of SO(2) and NO. Infrared spectroscopic results indicated the formation of both sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) species due to the catalytic role played by CeO(2). Apart from that, the catalytic activity of the RHA/CaO/CeO(2) sorbent was found to be closely related to its physical properties (specific surface area, total pore volume and average pore diameter).

Evaluation of various additives on the preparation of rice husk ash (RHA)/CaO-based sorbent for flue gas desulfurization (FGD) at low temperature.

This paper examines the effectiveness of 10 additives toward improving SO2 sorption capacities (SSC) of rice husk ash (RHA)/lime (CaO) sorbent. The additives examined are NaOH, CaCl2, LiCl, NaHCO3, NaBr, BaCl2, KOH, K2HPO4, FeCl3 and MgCl2. Most of the additives tested increased the SSC of RHA/CaO sorbent, whereby NaOH gave highest SSC (30mg SO2/g sorbent) at optimum concentration (0.25mol/l) compared to other additives examined. The SSC of RHA/CaO sorbent prepared with NaOH addition was also increases from 17.2 to 39.5mg SO2/g sorbent as the water vapor increases from 0% RH to 80% RH. This is probably due to the fact that most of additives tested act as deliquescent material, and its existence increases the amount of water collected on the surface of the sorbent, which played an important role in the reaction between the dry-type sorbent and SO2. Although most of the additives were shown to have positive effect on the SSC of the RHA/CaO sorbent, some were found to have negative or insignificant effect. Thus, this study demonstrates that proper selection of additives can improve the SSC of RHA/CaO sorbent significantly.

Anaerobic wastewater treatment using anaerobic baffled bioreactor: a review

Anaerobic wastewater treatment is receiving renewed interest because it offers a means to treat wastewater with lower energy investment. Because the microorganisms involved grow more slowly, such systems require clever design so that the microbes have sufficient time with the substrate to complete treatment without requiring enormous reactor volumes. The anaerobic baffled reactor has inherent advantages over single compartment reactors due to its circulation pattern that approaches a plug flow reactor. The physical configuration of the anaerobic baffled reactor enables significant modifications to be made; resulting in a reactor which is proficient of treating complex wastewaters which presently require only one unit, ultimately significant reducing capital costs. This paper also concerns about mechanism, kinetic and hydrodynamic studies of anaerobic digestion for future application of the anaerobic baffled reactor for wastewater treatment.

Sorption of SO2 and NO from simulated flue gas over rice husk ash (RHA)/CaO/CeO2 sorbent: Evaluation of deactivation kinetic parameters

In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO(2) sorbent for SO(2) and NO sorptions were investigated in a laboratory-scale stainless steel fixed-bed reactor. Data experiments were obtained from our previous results and additional independent experiments were carried out at different conditions. The initial sorption rate constant (k(0)) and deactivation rate constant (k(d)) for SO(2)/NO sorptions were obtained from the nonlinear regression analysis of the experimental breakthrough data using deactivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 °C. The activation energy and frequency factor for the SO(2) sorption were found to be 18.0 kJ/mol and 7.37 × 10(5)cm(3)/(g min), respectively. Whereas the activation energy and frequency factor for the NO sorption, were estimated to be 5.64 kJ/mol and 2.19 × 10(4)cm(3)/(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO(2)/NO sorptions.

Parameters optimization of rice husk ash (RHA)/CaO/CeO2 sorbent for predicting SO2/NO sorption capacity using response surface and neural network models

In this work, the application of response surface and neural network models in predicting and optimizing the preparation variables of RHA/CaO/CeO(2) sorbent towards SO(2)/NO sorption capacity was investigated. The sorbents were prepared according to central composite design (CCD) with four independent variables (i.e. hydration period, RHA/CaO ratio, CeO(2) loading and the use of RHA(raw) or pretreated RHA(600 degrees C) as the starting material). Among all the variables studied, the amount of CeO(2) loading had the largest effect. The response surface models developed from CCD was effective in providing a highly accurate prediction for SO(2) and NO sorption capacities within the range of the sorbent preparation variables studied. The prediction of CCD experiment was verified by neural network models which gave almost similar results to those determined by response surface models. The response surface models together with neural network models were then successfully used to locate and validate the optimum hydration process variables for maximizing the SO(2)/NO sorption capacities. Through this optimization process, it was found that maximum SO(2) and NO sorption capacities of 44.34 and 3.51 mg/g, respectively could be obtained by using RHA/CaO/CeO(2) sorbents prepared from RHA(raw) with hydration period of 12h, RHA/CaO ratio of 2.33 and CeO(2) loading of 8.95%.

Recycled paper mill effluent treatment in a modified anaerobic baffled reactor: start-up and steady-state performance

Start-up period is considered to be the most unstable and difficult stage in anaerobic process and usually takes a long time due to slow-degree adaptation of anaerobic microorganisms. In order to achieve a shorter start-up period, a novel modified anaerobic baffled reactor (MABR) has been developed in this study, where each modified baffle has its own characteristics (form/shape) to facilitate a treatment of recycled paper mill effluent (RPME). The results of physico-chemical characteristics showed that effluent from recycled paper mill consisted of 4328 mg L−1 chemical oxygen demand (COD), 669 mg L−1 biochemical oxygen demand and 501 mg L−1 volatile fatty acid. It also consisted of variety of heavy metals such as zinc, magnesium, iron and nickel at concentrations of 1.39, 12.19, 2.39 and 0.72 mg L−1, respectively. Performance of MABR during the start-up period showed that methane production reached 34.7% with COD removal of 85% at steady state. The result indicates that MABR was successfully operated during the start-up period in treating RPME within a period of less than 30 days.

Pharmaceutical residues in aquatic environment and water remediation by TiO 2 heterogeneous photocatalysis: a review

The occurrence of pharmaceutical compounds in the natural water sources has been reported as early as in the year 1980. Until now, the presence of pharmaceutical compounds in the aquatic environment has been frequently reported in the literature. Moreover, increasing evidence suggests that these contaminants have posed a threat to both humans and ecosystems. In this regard, the present review paper seeks to offer an overview of this environmental issue of pharmaceutical pollution where the subject matters to be reviewed include the effects, sources and mitigation strategies of pharmaceuticals in the aquatic environment. Besides, a review of the fundamentals and mechanisms of heterogeneous photocatalysis technology is also presented in this paper. Heterogeneous photocatalysis is a rapidly expanding technology which has been extensively investigated and applied in wastewater treatment for the remediation of persistent pollutants such as pharmaceutical compounds during the last decade. Furthermore, the ideal photocatalyst titanium dioxide (TiO2), which can collaborate and perform well in the photocatalysis treatment process, is also discussed. The advantages and limitations associated with the application of this treatment method are summarized and discussed in details. Finally, this review paper focuses on the future trend of the photocatalysis technology and identifies the barriers and lacking parts which need to be resolved in the near future.

Review of the mechanism and operational factors influencing the degradation process of contaminants in heterogenous photocatalysis

This paper presents a review of the principles and mechanisms involved in the process of heterogenous photocatalysis. The goal of photocatalysis is to remove persistent organic pollutants as well as microorganisms present in contaminated water. With the help of a semiconductor photocatalyst, solar photons are utilised to generate electron–hole pairs in the oxidation process, forming hydroxyl and superoxide radicals. There are several types of semiconductor photocatalyst available, the most widely used being titanium dioxide (TiO2). The effects of various operating factors influencing the photocatalytic degradation of pollutants, such as pH, catalyst concentration, substrate concentration, light intensity and wavelength, and oxidising agents are discussed. Heterogenous photocatalysis technology has been used in wastewater treatment during the last decade, and has been growing in efficiency ever since. From previous studies of different applications, it will be shown that this process is simple, cost-effective, sustainable and environmentally friendly. However, there are some minor disadvantages associated with its use in water purification, which are presented in this paper.

Application of a pre-hydrolyzed iron coagulant on partially stabilized leachate

AbstractLeachate is a liquid produced from the biodegradation of solid waste in landfill and is normally referred as highly polluted wastewater. Various treatment methods are available and it is highly depended on the characteristics of the leachate. One of the common and simplest methods is using coagulation process. The application of pre-hydrolyzed coagulants in coagulation process is well known for water and wastewater treatment. However, information on the application of pre-hydrolyzed coagulants, especially pre-hydrolyzed iron (PHI), in partially stabilized leachate treatments is not well documented. This study examined the application of PHI on the partially stabilized leachate by determining the optimum basicity ratio, pH, and dose through the removals percentage of suspended solid (SS), color, and chemical oxygen demand (COD). Laboratory jar tests revealed that the optimum PHI basicity ratio, pH, and dosage were 0.1, 5, and 0.2 g/L Fe, respectively. The optimum removals of SS, color, and COD were...