Anaerobic digestion (AD) can remove substantial amount of organic load when applied in treating d... more Anaerobic digestion (AD) can remove substantial amount of organic load when applied in treating distillery effluent but it is ineffective in colour reduction. Conversely, photodegradation is effective in colour reduction but has high energy requirement. A study on the synergy of a combined AD and ultra violet (UV) photodegradation treatment of distillery effluent was carried out in fluidized bed reactors to evaluate pollution reduction and energy utilization efficiencies. The combined process improved colour removal from 41% to 85% compared to that of AD employed as a stand-alone process. An overall corresponding total organic carbon (TOC) reduction of 83% was achieved. The bioenergy production by the AD step was 14.2 kJ/g total organic carbon (TOC) biodegraded while UV lamp energy consumption was 0.9 kJ/mg TOC, corresponding to up to 100% colour removal. Electrical energy per order analysis for the photodegradation process showed that the bioenergy produced was 20% of that required by the UV lamp to photodegrade 1 m(3) of undiluted pre-AD treated effluent up to 75% colour reduction. It was concluded that a combined AD-UV system for treatment of distillery effluent is effective in organic load removal and can be operated at a reduced cost.
Ultra-Violet (UV) photocatalytic degradation and anaerobic digestion (AD) were applied in the tre... more Ultra-Violet (UV) photocatalytic degradation and anaerobic digestion (AD) were applied in the treatment of methylene blue (MB) dye. South African natural zeolite was used as a catalyst support and biomass support in the photocatalysis and AD process respectively. It was found that UV photocatalysis pre-treatment of MB dye before the AD process improved its biodegradability. This resulted in higher biogas production coefficient compared to the non-UV pre-treated MB dye.
... Mike Masukume 1 , Maurice S. Onyango 1 , Ochieng Aoyi 2 and Fred Otieno 3 ... Column study an... more ... Mike Masukume 1 , Maurice S. Onyango 1 , Ochieng Aoyi 2 and Fred Otieno 3 ... Column study and breakthrough analysis were carried out to get an understanding of the effects of inlet flow rate, adsorbent mass, initial concentration and column diameter on the adsorption of ...
The formation of colored intermediate compounds during photocatalytic degradation of phenol repre... more The formation of colored intermediate compounds during photocatalytic degradation of phenol represents the risk of single-handedly employing ultraviolet visible (UV-Vis) spectrophotometry for the determination of residual phenol concentration. Moreover, the widely used titania (TiO2) photocatalyst is hindered by the high recombination rate of electron-hole pairs. In this study, phenol was photodegraded in the presence of sol gel synthesized TiO2 and silver doped titania (Ag-TiO2), under UV illumination. Spectrophotometric determination of residual phenol concentration was done using high performance liquid chromatography (HPLC) and UV-Vis spectrophotometry. Scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) spectroscopies revealed the successful introduction of the Ag dopant into the TiO2 lattice. The UV-Vis and photoluminescence (PL) spectroscopic analyses revealed restrained electron hole-pair recombination and reduced energy bandgap in Ag-TiO2. Ag-TiO2 showed better photocatalytic efficiency than TiO2, in line with the observed optical properties. Optimal conditions of 3% dopant loading, initial pH of 4 and catalyst loading of 1 g/L were determined for the degradation process. Formation of colored intermediates resulted in higher analytical values for residual phenol obtained from UV-Vis as compared to those obtained from HPLC analyses. For high affirmation of the reproducibility of photodegradation results, UV-Vis spectrophotometry should, therefore, be employed alongside other analytical techniques.
Journal of environmental chemical engineering, Jun 1, 2016
Abstract Coal, just like other fossil fuels such as oil and natural gas, is mainly used as a non-... more Abstract Coal, just like other fossil fuels such as oil and natural gas, is mainly used as a non-renewable source of energy. It is a physically unique mineral resource almost totally composed of organic matter (carbon), and a smaller percentage of elements such as hydrogen, oxygen, sulphur, and nitrogen. It is believed that underground coal deposits formed about 250–300 million years ago, when much of the Earth was a swamp covered with thick forest and plant growth. This review explores the use of coal, not as an energy source used for generating electricity, but as a low cost adsorbent in water and wastewater treatment processes. In fact, today, coal-based adsorbents still attract considerable interest in their usage. The review critically analyses the chemical composition, ion-exchange and sorption properties of coal. The use of the as-received coals, demineralized coals, sulphonated coals, calcium-loaded coals, chitosan-doped coals, activated carbon, coal fly ash, and coal fly ash derived-zeolite has also been extensively discussed. It is evident from this review that although the pollutant exchange capacities of various types of coal-based adsorbents are significantly lower in comparison to other forms of adsorbents, the substantially lower cost of coal shows a great potential for the utilization of coal as a means to remove a range of pollutants from water and wastewater effluents. However, due to the scarcity of consistent cost information, cost comparisons are difficult to make, and consequently, in this review, such comparisons were not done for the coal-based adsorbents.
This work involves the treatment of model groundwater containing arsenic with the use of chemical... more This work involves the treatment of model groundwater containing arsenic with the use of chemically modified zeolite. A finite volume stirred tank reactor was used to study the effects of the variables; sorbent grain fraction and sorbent dose, on arsenic reaction kinetics. The results are modelled using the pseudo-second order and second-order reversible rate equations. Equilibrium arsenic uptake and residual sum of squares evaluated from the two models are compared. From them, the arsenic sorption onto the active sites is consistent with a pseudo-second order mechanism. The initial sorption rate which drives the uptake rate was found to be in the same order of magnitude for all the grain fractions but decreased with an increase in the sorbent dose. Furthermore, based on the pseudo-second order mechanism, Thiele moduli were determined and their values suggested that intraparticle diffusion may play a significant role in arsenic uptake.
Anaerobic digestion (AD) can remove substantial amount of organic load when applied in treating d... more Anaerobic digestion (AD) can remove substantial amount of organic load when applied in treating distillery effluent but it is ineffective in colour reduction. Conversely, photodegradation is effective in colour reduction but has high energy requirement. A study on the synergy of a combined AD and ultra violet (UV) photodegradation treatment of distillery effluent was carried out in fluidized bed reactors to evaluate pollution reduction and energy utilization efficiencies. The combined process improved colour removal from 41% to 85% compared to that of AD employed as a stand-alone process. An overall corresponding total organic carbon (TOC) reduction of 83% was achieved. The bioenergy production by the AD step was 14.2 kJ/g total organic carbon (TOC) biodegraded while UV lamp energy consumption was 0.9 kJ/mg TOC, corresponding to up to 100% colour removal. Electrical energy per order analysis for the photodegradation process showed that the bioenergy produced was 20% of that required by the UV lamp to photodegrade 1 m(3) of undiluted pre-AD treated effluent up to 75% colour reduction. It was concluded that a combined AD-UV system for treatment of distillery effluent is effective in organic load removal and can be operated at a reduced cost.
Ultra-Violet (UV) photocatalytic degradation and anaerobic digestion (AD) were applied in the tre... more Ultra-Violet (UV) photocatalytic degradation and anaerobic digestion (AD) were applied in the treatment of methylene blue (MB) dye. South African natural zeolite was used as a catalyst support and biomass support in the photocatalysis and AD process respectively. It was found that UV photocatalysis pre-treatment of MB dye before the AD process improved its biodegradability. This resulted in higher biogas production coefficient compared to the non-UV pre-treated MB dye.
... Mike Masukume 1 , Maurice S. Onyango 1 , Ochieng Aoyi 2 and Fred Otieno 3 ... Column study an... more ... Mike Masukume 1 , Maurice S. Onyango 1 , Ochieng Aoyi 2 and Fred Otieno 3 ... Column study and breakthrough analysis were carried out to get an understanding of the effects of inlet flow rate, adsorbent mass, initial concentration and column diameter on the adsorption of ...
The formation of colored intermediate compounds during photocatalytic degradation of phenol repre... more The formation of colored intermediate compounds during photocatalytic degradation of phenol represents the risk of single-handedly employing ultraviolet visible (UV-Vis) spectrophotometry for the determination of residual phenol concentration. Moreover, the widely used titania (TiO2) photocatalyst is hindered by the high recombination rate of electron-hole pairs. In this study, phenol was photodegraded in the presence of sol gel synthesized TiO2 and silver doped titania (Ag-TiO2), under UV illumination. Spectrophotometric determination of residual phenol concentration was done using high performance liquid chromatography (HPLC) and UV-Vis spectrophotometry. Scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) spectroscopies revealed the successful introduction of the Ag dopant into the TiO2 lattice. The UV-Vis and photoluminescence (PL) spectroscopic analyses revealed restrained electron hole-pair recombination and reduced energy bandgap in Ag-TiO2. Ag-TiO2 showed better photocatalytic efficiency than TiO2, in line with the observed optical properties. Optimal conditions of 3% dopant loading, initial pH of 4 and catalyst loading of 1 g/L were determined for the degradation process. Formation of colored intermediates resulted in higher analytical values for residual phenol obtained from UV-Vis as compared to those obtained from HPLC analyses. For high affirmation of the reproducibility of photodegradation results, UV-Vis spectrophotometry should, therefore, be employed alongside other analytical techniques.
Journal of environmental chemical engineering, Jun 1, 2016
Abstract Coal, just like other fossil fuels such as oil and natural gas, is mainly used as a non-... more Abstract Coal, just like other fossil fuels such as oil and natural gas, is mainly used as a non-renewable source of energy. It is a physically unique mineral resource almost totally composed of organic matter (carbon), and a smaller percentage of elements such as hydrogen, oxygen, sulphur, and nitrogen. It is believed that underground coal deposits formed about 250–300 million years ago, when much of the Earth was a swamp covered with thick forest and plant growth. This review explores the use of coal, not as an energy source used for generating electricity, but as a low cost adsorbent in water and wastewater treatment processes. In fact, today, coal-based adsorbents still attract considerable interest in their usage. The review critically analyses the chemical composition, ion-exchange and sorption properties of coal. The use of the as-received coals, demineralized coals, sulphonated coals, calcium-loaded coals, chitosan-doped coals, activated carbon, coal fly ash, and coal fly ash derived-zeolite has also been extensively discussed. It is evident from this review that although the pollutant exchange capacities of various types of coal-based adsorbents are significantly lower in comparison to other forms of adsorbents, the substantially lower cost of coal shows a great potential for the utilization of coal as a means to remove a range of pollutants from water and wastewater effluents. However, due to the scarcity of consistent cost information, cost comparisons are difficult to make, and consequently, in this review, such comparisons were not done for the coal-based adsorbents.
This work involves the treatment of model groundwater containing arsenic with the use of chemical... more This work involves the treatment of model groundwater containing arsenic with the use of chemically modified zeolite. A finite volume stirred tank reactor was used to study the effects of the variables; sorbent grain fraction and sorbent dose, on arsenic reaction kinetics. The results are modelled using the pseudo-second order and second-order reversible rate equations. Equilibrium arsenic uptake and residual sum of squares evaluated from the two models are compared. From them, the arsenic sorption onto the active sites is consistent with a pseudo-second order mechanism. The initial sorption rate which drives the uptake rate was found to be in the same order of magnitude for all the grain fractions but decreased with an increase in the sorbent dose. Furthermore, based on the pseudo-second order mechanism, Thiele moduli were determined and their values suggested that intraparticle diffusion may play a significant role in arsenic uptake.
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