The adsorption characteristics of chromium ions in chrome electroplating wastewater on low cost adsorbent have been conducted. Adsorbent was prepared from bovine bone waste of NaOH activated at various concentrations (0.2 to 0.8 M). Its adsorption such as adsorption isotherms and adsorption thermodynamics as well as adsorbent physico-chemical characteristics (surface active sites, crystallinity and crystal size, surface morphology and elementals composition). The result showed that amount of adsorbent surface active sites increased because of NaOH activated, the highest at 0.4 M NaOH concentration (AT0.4 adsorbent). X-ray diffraction patterns of the adsorbents showed a wide peaks and crystal size as nanocrystalline. The surface morfology was stack of aglomerates and leached of Ca and Mg due to increase Na. The adsorption result of adsorbents to chromium ions showed that the highest adsorption ability on AT0.4 adsorbent. It was suitable for Freundlich adsorption isotherm model as physical adsorption and endothermic but the tendency to be spontaneous process.

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Biodiesel production from waste cooking oil in two steps reaction of esterification and transesterification is low efficient, due to twice methanol consumption and need more reaction time. Optimizing reaction conditions of CaO as a matrix of solid catalyst prepared from crab shell (green CaO) and modified by K2O/TiO2 for converting waste cooking oil to biodiesel have been carried out. Catalytic process of waste cooking oil to biodiesel took place in one step reaction of esterification and transesterification. The research result showed that optimum conditions in its one step reaction such as methanol to oil molar ratio was 9:1, amount of CaO/K2O-TiO2 catalyst to oil was 5% and reaction time of 60 minutes with biodiesel yield was 88.24%. Physical and chemical properties of biodiesel which produced from one step reaction of esterification and transesterification of waste cooking oil were suitable with Indonesian National Standard (SNI-04-7182-2006) namely density at 40oC of 850 kg/m3, kinematic viscosity at 40oC of 3.32 cSt, water content of 0.046%, iodine number of 59.25 g I2/100g and acid value of 0.29 mg KOH/g. Gas chromatography-mass spectrometry (GC-MS) analysis of biodiesel formed fatty acid methyl esters from conversion of waste cooking oil.