Gadjah Mada University

About: Gadjah Mada University is a education organization based out in Yogyakarta, Indonesia. It is known for research contribution in the topics: Population & Adsorption. The organization has 17307 authors who have published 21389 publications receiving 116561 citations. The organization is also known as: University of Gajah Mada & Universitas Gadjah Mada.

Adsorption of mercury(II) on dithizone-immobilized natural zeolite

Abstract: Adsorption of Hg(II) ions onto selective adsorbent of dithizone-immobilized natural zeolite (DIZ) from Wonosari, Yogyakarta, Indonesia has been investigated in batch mode. Some parameters influencing immobilization of dithizone and adsorption of Hg(II) were optimized including effect of temperature and reaction time on the effectiveness of dithizone immobilization as well as effect of pH, contact time and initial concentration of Hg(II) ion on the efficiency of the Hg(II) adsorption. Preliminary application of the adsorbent in the removal of Hg(II) ion in river water spiked with Hg(II) was also studied. The FT-IR and XRD analytical results show that the surface of natural zeolite can be modified by immobilization of selective organic ligand towards Hg(II) ions. The optimum conditions for the adsorption of Hg(II) is achieved at pH 5 and 90 min of contact time. Kinetics and adsorption isotherm studies suggest that the capacity, affinity and selectivity of the DIZ in adsorbing hazardous metal ions such as Hg(II) is significantly improved compared to those of non-immobilized activated natural zeolite (AZ). The Hg(II) adsorption capacity for AZ and DIZ at optimum condition is 8.0 and 13.1 μmol/g, respectively and the both adsorption follows first-order reaction. It has also been demonstrated that the DIZ adsorbent may be applied in the removal of Hg(II) ion in the river water spiked with Hg(II) ion up to 99.36% from the initial concentration of 8 mg L −1 in two serial batch adsorptions.

Coastal flood management in Semarang, Indonesia

Abstract: Semarang is one of the biggest cities in Indonesia and is nowadays suffering from coastal flooding. Land subsidences, high water tide, and inadequate structural measures play important roles in the coastal inundations. Structural and non-structural methods for controlling coastal flooding including dykes, drainage systems, pump stations, polder systems, coastal-land reclamations, coastal planning and management, public education, as well as the establishment of an institutional framework for disaster management have been implemented in the Semarang coastal area. Although some improvements have been made, the current flood management system has generally failed to address a wide range of coastal inundation problems. Some improvement actions have been proposed including stakeholders involvement on the disaster mitigation. For a long period coastal management, accelerated sea level rises due to global warming should also be taken into account.

Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour

Abstract: Dome-forming volcanoes are among the most hazardous volcanoes on Earth. Magmatic outgassing can be hindered if the permeability of a lava dome is reduced, promoting pore pressure augmentation and explosive behaviour. Laboratory data show that acid-sulphate alteration, common to volcanoes worldwide, can reduce the permeability on the sample lengthscale by up to four orders of magnitude and is the result of pore- and microfracture-filling mineral precipitation. Calculations using these data demonstrate that intense alteration can reduce the equivalent permeability of a dome by two orders of magnitude, which we show using numerical modelling to be sufficient to increase pore pressure. The fragmentation criterion shows that the predicted pore pressure increase is capable of fragmenting the majority of dome-forming materials, thus promoting explosive volcanism. It is crucial that hydrothermal alteration, which develops over months to years, is monitored at dome-forming volcanoes and is incorporated into real-time hazard assessments.