Tonni Agustiono Kurniawan

Low-cost adsorbents for heavy metals uptake from contaminated water: a review

In this article, the technical feasibility of various low-cost adsorbents for heavy metal removal from contaminated water has been reviewed. Instead of using commercial activated carbon, researchers have worked on inexpensive materials, such as chitosan, zeolites, and other adsorbents, which have high adsorption capacity and are locally available. The results of their removal performance are compared to that of activated carbon and are presented in this study. It is evident from our literature survey of about 100 papers that low-cost adsorbents have demonstrated outstanding removal capabilities for certain metal ions as compared to activated carbon. Adsorbents that stand out for high adsorption capacities are chitosan (815, 273, 250 mg/g of Hg(2+), Cr(6+), and Cd(2+), respectively), zeolites (175 and 137 mg/g of Pb(2+) and Cd(2+), respectively), waste slurry (1030, 560, 540 mg/g of Pb(2+), Hg(2+), and Cr(6+), respectively), and lignin (1865 mg/g of Pb(2+)). These adsorbents are suitable for inorganic effluent treatment containing the metal ions mentioned previously. It is important to note that the adsorption capacities of the adsorbents presented in this paper vary, depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentration of adsorbate.

Removal of Co(II) and Ni(II) ions from contaminated water using silica gel functionalized with EDTA and/or DTPA as chelating agents.

In this study, the removal of Co(II) and Ni(II) ions from contaminated water was investigated using silica gel materials functionalized with both ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA). The modified adsorbents were characterized using elemental analysis, surface area and pore size analysis, and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode. The optimum conditions for the removal of both metals at an initial concentration of 10mg/L were 2g/L of dose, pH 3, 50 rpm of agitation speed and 4h of contact time. The removal of Co(II) and Ni(II) by EDTA- and/or DTPA-modified silica gels was substantially higher than that by their unmodified form. The maximum Co(II) and Ni(II) uptakes by the EDTA-modified silica gel were 20.0 and 21.6 mg/g, comparable to their adsorption capacities by DTPA-modified silica gel (Co(II): 16.1mg/g; Ni(II): 16.7 mg/g). At the same concentration of 10mg/L, the removal of both metals by the modified adsorbents ranged from 96% to 99%. The two-site Langmuir model was representative to simulate adsorption isotherms. The kinetics of Co(II) and Ni(II) adsorption by modified silica gels followed pseudo-second-order.

Removal of refractory compounds from stabilized landfill leachate using an integrated H2O2 oxidation and granular activated carbon (GAC) adsorption treatment.

This study investigated the treatment performances of H(2)O(2) oxidation alone and its combination with granular activated carbon (GAC) adsorption for raw leachate from the NENT landfill (Hong Kong) with a very low biodegradability ratio (BOD(5)/COD) of 0.08. The COD removal of refractory compounds (as indicated by COD values) by the integrated H(2)O(2) and GAC treatment was evaluated, optimized and compared to that by H(2)O(2) treatment alone with respect to dose, contact time, pH, and biodegradability ratio. At an initial COD concentration of 8000 mg/L and NH(3)-N of 2595 mg/L, the integrated treatment has substantially achieved a higher removal (COD: 82%; NH(3)-N: 59%) than the H(2)O(2) oxidation alone (COD: 33%; NH(3)-N: 4.9%) and GAC adsorption alone (COD: 58%) at optimized experimental conditions (p< or =0.05; t-test). The addition of an Fe(II) dose at 1.8 g/L further improved the removal of refractory compounds by the integrated treatment from 82% to 89%. Although the integrated H(2)O(2) oxidation and GAC adsorption could treat leachate of varying strengths, treated effluents were unable to meet the local COD limit of less than 200 mg/L and the NH(3)-N of lower than 5 mg/L. However, the integrated treatment significantly improved the biodegradability ratio of the treated leachate by 350% from 0.08 to 0.36, enabling the application of subsequent biological treatments for complementing the degradation of target compounds in the leachate prior to their discharge.

Degradation of chelating agents in aqueous solution using advanced oxidation process (AOP)

This article presents an overview with critical analysis of technical applicability of advanced oxidation process (AOP) in removing chelating agents from aqueous solution. Apart from the effect of metals for chelating agents as a major influencing factor, selected information such as pH, oxidants dose, concentrations of pollutants and treatment performance is presented. The performance of individual AOP is compared. It is evident from our literature survey that photocatalysis with UV irradiation alone or coupled with TiO(2), ozonation and Fentons oxidation are frequently applied to mineralize target pollutants. Overall, the selection of the most suitable AOP depends on the characteristics of effluents, technical applicability, discharge standard, regulatory requirements and environmental impacts.

Modeling biogas production from organic fraction of MSW co-digested with MSWI ashes in anaerobic bioreactors

This study aims at investigating the effects of MSW incinerator fly ash (FA) and bottom ash (BA) on the anaerobic co-digestion of OFMSW with FA or BA. It also simulates the biogas production from various dosed and control bioreactors. Results showed that suitable ashes addition (FA/MSW 10 and 20 g L(-1) and BA/MSW 100 g L(-1)) could improve the MSW anaerobic digestion and enhance the biogas production rates. FA/MSW 20 g L(-1) bioreactor had the higher biogas production and rate implying the potential option for MSW anaerobic co-digestion. Modeling studies showed that exponential plot simulated better for FA/MSW 10 g L(-1) and control bioreactors while Gaussian plot was applicable for FA/MSW 20 g L(-1) one. Linear and exponential plot of descending limb both simulated better for BA/MSW 100 g L(-1) bioreactor. Modified Gompertz plot showed higher correlation of biogas accumulation than exponential rise to maximum plot for all bioreactors.

Nanoadsorbents for Remediation of Aquatic Environment: Local and Practical Solutions for Global Water Pollution Problems

The authors present an overview with critical analysis of technical applicability of various nanoadsorbents such as carbon nanotubes, nano-zerovalent iron, and metal oxides–based and polymeric nanoparticles in treating contaminated water. To highlight their performance, selected information such as synthesis method, pH, dose required, pollutants concentrations, reaction time, and treatment efficiency is presented based on the literature survey of 276 articles (1989–2010). Their advantages and drawbacks in applications are evaluated. Nanoadsorbents that stand out for outstanding performance are compared to bulk activated carbon. The implications of nanoadsorbents to public health and their way forward for facilitating environmental sustainability are also discussed.

Biological processes for treatment of landfill leachate

This review presents an overview with critical analysis of the technical applicability of biological treatments for landfill leachate. A particular focus is given to activated sludge (AS), sequencing batch reactors (SBR), aerated lagoons (AL), and upflow anaerobic sludge blankets (UASB). Their advantages and limitations in application are evaluated. Selected information is presented such as pH, hydraulic retention time (HRT), organic loading rate (OLR), characteristics of leachate and treatment performance. It is evident from the literature survey of 188 papers (1976-2010) that none of the individual biological treatments presented is universally applicable for removing recalcitrant contaminants from leachate. Among the biological treatments reviewed, AS, SBR and UASB are the most frequently applied. These treatments are effective not only to remove over 90% of COD with a concentration ranging from 3500-26 000 mg L(-1), but also to achieve 80% of NH(3)-N removal with a concentration ranging from 100-1000 mg L(-1). A combination of physico-chemical and biological treatment into an integrated process is effective for leachate treatment. Almost complete removal of COD and NH(3)-N was reported for combined reverse osmosis (RO) and UASB with an initial COD concentration of 35 000 mg L(-1) and NH(3)-N concentration of 1600 mg L(-1). Integrated Fentons oxidation and AS could achieve about 98% and 99% of COD and NH(3)-N removal, respectively, with initial COD and NH(3)-N concentrations of 7000 mg L(-1) and 1800 mg L(-1). Overall, the selection of the most suitable treatment for leachate depends on its characteristics, technical applicability and potential constraints, effluent limit required, cost-effectiveness, regulatory requirements and long-term environmental impacts.

Effects of spiked metals on the MSW anaerobic digestion

This study aimed to investigate the effects of eight metals on the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) in bioreactors. Anaerobic bioreactors containing 200 mL MSW mixed completely with 200 mL sludge seeding. Ca and K (0, 1000, 2000 and 6000 mg L−1) and Cr, Ni, Zn, Co, Mo and W (0, 5, 50 and 100 mg L−1) of various dose were added to anaerobic bioreactors to examine their anaerobic digestion performance. Results showed that except K and Zn, Ca (~728 to ~1461 mg L−1), Cr (~0.0022 to ~0.0212 mg L−1), Ni (~0.801 to ~5.362 mg L−1), Co (~0.148 to ~0.580 mg L−1), Mo (~0.044 to ~52.94 mg L−1) and W (~0.658 to ~40.39 mg L−1) had the potential to enhance the biogas production. On the other hand, except Mo and W, inhibitory concentrations IC50 of Ca, K, Cr, Ni, Zn and Co were found to be ~3252, ~2097, ~0.124, ~7.239, ~0.482, ~8.625 mg L−1, respectively. Eight spiked metals showed that they were adsorbed by MSW to a different extent resulting in different liquid metals levels and potential stimulation and inhibition on MSW anaerobic digestion. These results were discussed and compared to results from literature.

Treatment of Contaminated Water Laden with 4-Chlorophenol using Coconut Shell Waste-Based Activated Carbon Modified with Chemical Agents

This laboratory study investigates the performances of coconut shell waste-based activated carbon (CSBAC) in removing 4-chlorophenol (4-CP) from contaminated water. To improve its removal for target compound, the surface of CSBAC was modified with TiO2, NaOH, and/or HNO3. Under optimized conditions at the same initial concentration of 25 mg/L, the NaOH-treated CSBAC could remove 91% of 4-CP, compared to the HNO3-oxidized CSBAC (60%) or the TiO2-coated CSBAC (72%). Although the NaOH-treated CSBAC could remove 91% of 4-CP, the adsorption treatment using this adsorbent alone was unable to meet the effluent limit of lower than 1 mg/L. Therefore, subsequent biological processes are required to complement the removal of 4-CP from wastewater.